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Startle Probe Modality: An Investigation of Ethnic Differences


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STARTLE PROBE MODALITY: AN INVE STIGATION OF ETHNIC DIFFERENCES By KATHRYN S. GRAY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2004

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Copyright 2004 by Kathryn S. Gray

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ACKNOWLEDGMENTS I thank my advisor, Lisa M. Brown, for her guidance, advice, and unbridled enthusiasm for the field of social psychology and for life in general. I owe a great deal of gratitude to Margaret Bradley, Peter Lang, and the NIMH Center for the Study of Emotion and Attention for graciously allowing me to utilize their facilities. I thank my committee members, Margaret Bradley, James Algina, and James Shepperd, for their thoughtful comments and suggestions on this thesis. I am forever grateful to my parents for a lifetime of support, encouragement, and unconditional love. I thank Mike Bolen for listening, offering support, and being my best friend. I owe a deep appreciation to Mr. Kreinbihl, my 4 th grade math teacher, who sparked my interest in mathematics; Mr. Pekich, my 11 th grade Chemistry II teacher, who introduced me to the world of research and good science; my brother, Mark, who inspires me in general, but who provided the foundation for my fascination with psychology; and to people in general who not only prompted my interest in social psychology, but who give me the opportunity to study and apply social psychology each day of my life. iii

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TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF FIGURES...........................................................................................................vi ABSTRACT......................................................................................................................vii CHAPTER 1 INTRODUCTION........................................................................................................1 Emotion.........................................................................................................................2 Startle............................................................................................................................3 Affect and Startle...................................................................................................4 Startle Probe Modality...........................................................................................6 Ethnic Differences in Physiology.................................................................................6 Rationale for Current Study..........................................................................................7 Research Question........................................................................................................8 Hypotheses....................................................................................................................9 Ethnic Differences in Startle.................................................................................9 Affective Modulation............................................................................................9 2 METHOD...................................................................................................................10 Participants.................................................................................................................10 Materials and Design..................................................................................................10 Stimuli.................................................................................................................10 Startle Probes.......................................................................................................12 Hearing Test........................................................................................................12 Questionnaires.....................................................................................................13 Startle Eyeblink Measurement and Reduction...........................................................13 Procedure....................................................................................................................14 Analyses......................................................................................................................15 3 RESULTS...................................................................................................................17 Magnitude...................................................................................................................17 Probe Modality....................................................................................................17 Valence................................................................................................................17 iv

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Ethnicity..............................................................................................................19 Probability...................................................................................................................21 Probe Modality....................................................................................................21 Valence................................................................................................................21 Ethnicity..............................................................................................................22 Amplitude...................................................................................................................23 Probe Modality....................................................................................................23 Valence................................................................................................................23 Ethnicity..............................................................................................................24 Tests of Alternative Explanations...............................................................................24 Hearing................................................................................................................24 Subjective Ratings of Startle Probes...................................................................25 4 DISCUSSION.............................................................................................................27 5 CONCLUSION...........................................................................................................32 APPENDIX A PERSONAL NEED FOR STRUCTURE SCALE.....................................................33 B INTERACTION AND AUDIENCE ANXIOUSNESS SCALE................................34 C POST-EXPERIMENTAL QUESTIONNAIRE.........................................................35 LIST OF REFERENCES...................................................................................................38 BIOGRAPHICAL SKETCH.............................................................................................42 v

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LIST OF FIGURES Figure page 3-1 Startle blink magnitude............................................................................................18 3-2 Startle blink magnitude obtained from European American and African American participants ..............................................................................................................20 3-3 The probability of a startle response........................................................................22 3-4 Startle blink amplitude............................................................................................24 3-5 Mean hearing thresholds for each ethnic group at each frequency level.................25 vi

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science STARTLE PROBE MODALITY: AN INVESTIGATION OF ETHNIC DIFFERENCES By Kathryn S. Gray August 2004 Chair: Lisa M. Brown, Ph.D. Major Department: Psychology Ethnic differences in the startle response were assessed. Eyeblink reflexes for European Americans and African Americans were examined in response to acoustic (bursts of noise) and visual (flashes of light) startle probes while viewing 36 pictures representing pleasant, neutral, or unpleasant content. An effect of picture valence was obtained for both ethnic groups in response to both acoustic and visual startle probes. The ethnic groups did not differ in startle reflex probability, magnitude, or amplitude. Taken together, the results suggest that the startle response is a reliable measure of emotion for European Americans and African Americans whether elicited by acoustic or visual startle probes. vii

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CHAPTER 1 INTRODUCTION Imagine sitting at home alone, watching a horror movie. It is late at night. The sky is pitch black except for an intermittent flash of lightening. Raindrops are pounding against the window and tree branches are violently blowing in the wind. All of a sudden, a loud crash of thunder makes you literally jump out of your chair. For a brief moment, you experience a feeling of fear and your body prepares itself for anticipated action. The emotional experience accompanying the physical response serves as a warning that action may be required. Is there an intruder smashing your window? Should you run? Do you need to protect yourself? Your physical response and corresponding emotional state would likely be different if you were watching a comedy film, opposed to a horror movie, at the time the thunder crashed. The preexisting apprehension experienced while viewing a horror movie (in contrast to the relaxed, jovial state experienced while viewing a comedy) exaggerates the physical reaction elicited in response to a sudden, potentially threatening, stimulus. Thus, preexisting emotional states can influence subsequent physiological responses. A wealth of research exists examining emotional and physiological responses in humans. However, despite evidence suggesting ethnic differences in emotional experiences and physiological responses, research on the possibility of ethnic differences in the startle response, specifically, is lacking. Research shows that emotional experiences are influenced by culture (Matsumoto, 1993). Cultures differ in terms of what is considered appropriate emotional expression (Matsumoto, 1990) as well as actual display of emotion (Ekman, 1971; Friesen, 1972, as 1

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2 cited by Matsumoto, 1993). Cultures also differ when judging faces and labeling which emotion they perceive (Matsumoto, 1993). In addition, studies show cultural differences in the subjective experience of emotion, including self-reported emotional experience (e.g., intensity, duration, and control of emotion); verbal and nonverbal expressions; and physiological sensations and reactions (Scherer et al., 1988; Matsumoto et al., 1988). Investigating cultural differences by comparing samples from different countries is a common practice in cross-cultural research on emotion. Although important information is gained by examining international differences, exploring intranational differences is also a fruitful endeavor, especially in ethnically diverse nations such as the United States. Emotion Humans desire to attain pleasant things and to avoid unpleasant things. This hedonistic orientation is not merely a means of self-gratification, but is adaptive in that it functions to promote survival. In humans, the behaviors of moving toward positive things and moving away from negative things are accompanied by emotion (Bradley & Lang, 2000). In addition to reported feelings (e.g., happiness, sadness, fear, anger, and love), emotions possess a biological component, regarded by many theorists as a product of evolution (e.g., Davis & Lang, 2003; Frijda, 1986; Izard, 1977). Emotions function to promote survival and reproduction by signaling situations that require immediate attention, motivating adaptive behaviors, and serving as tools for communication (Leary, Koch, & Hechenbleikner, 2001). Researchers propose a two-factor motivational organization of emotion, suggesting that emotions are organized as responses to stimuli that are either generally positive (appetitive) or negative (aversive) in nature (Dickinson & Dearing, 1979; Konorski, 1967; Lang, Bradley, & Cuthbert, 1998). According to the

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3 motivational organization proposed by Lang et al. (1998), situations that promote survival (e.g., copulation) prime the activation of the appetitive system, whereas situations involving threat (e.g., attack) prime the activation of the defensive system. To scientifically study emotions and the underlying motivational systems, they must be measurable. Emotions can be organized into three measurable systems: language (e.g., cries of distress, self-reported descriptions of feelings), physiological reactions (e.g., heart rate, skin conductance change, reflexes), and behaviors (e.g., approach, avoidance) (Lang, 1993). The elicitation of measurable behavioral responses (e.g., fleeing the room) is difficult, if not impossible, under the current ethical guidelines. Self-report data are often susceptible to social desirability, and people may not always be capable of accurately identifying and reporting their own emotional responses (especially physiological reactions such as subtle changes in facial muscle tension). Thus, poor levels of covariation between these systems often occur (Bradley & Lang, 2000). Although self-report data are useful, it may be helpful for researchers interested in the physiological correlates of emotion to employ physiological measures to acquire supplementary data that self-report measures alone are unable to provide. Startle When presented with a sudden threatening stimulus (e.g., a loud crash of thunder), the defensive system quickly responds with a startle response, or startle reflex, to protect the body from potential injury. The startle response consists of a behavioral repertoire, including: hunching of the shoulders, pulling the head down and forward, clenching of the fists, and quickly closing the eyes (i.e., blinking) (Hunt & Clarke, 1937). The eyeblink is the most stable component of the startle response (Bradley & Lang, 2000; Lang, Bradley, & Cuthbert, 1990) and can be measured by electrodes placed below the

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4 eye, over the orbicularis oculi (the muscle responsible for the eyeblink). Researchers conducting psychophysiological research often utilize the eyeblink as one measure of the startle reflex, and thus, as an indicator that the defensive system is engaged. The startle response serves as a defensive reflex that is heightened in situations providing evidence of threat or other potential harm (e.g., attack) and is inhibited (or decreased) in contexts promoting survival (e.g., sustenance) (Bradley, Cuthbert, & Lang, 1999). Thus, the startle reflex provides one useful physiological measure in the study of emotion. Researchers use a number of measures to quantify the startle response. Startle probability provides information regarding the likelihood of a startle reflex. Startle magnitude provides a useful measure of startle size by averaging across all trials, even trials where no startle reflex occurred. However, a significant difference in startle magnitude between two groups may be caused by 1) the actual size of the startle response being larger in one group compared to the other, 2) the probability of a startle response being greater in one group compared to the other, or 3) both 1 and 2. In contrast to magnitude, which includes all trials, startle amplitude includes only trials where a valid startle response occurred. Amplitude provides information regarding the actual size of the startle response, controlling for possible differences in the probability of a response. Affect and Startle The viewing of emotionally laden stimuli (such as photographs from the International Affective Picture System) is accompanied by a motivational state commensurate with the affective content of the picture. For example, a stimulus that indicates potential threat produces a defensive motivational state, whereas a stimulus signifying pleasantness produces a positive, or appetitive, motivational state. The emotional reactions associated with each motivational state affect the degree to which the

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5 startle reflex is exhibited in response to a startle probe (e.g., a burst of noise, a bright light). That is, the affective valence (i.e., degree of pleasantness or unpleasantness) of the stimulus affects the elicited startle reflex in very predictable ways. Consistent with the previously mentioned motivational priming hypothesis proposed by Lang et al. (1998), the standard finding in psychophysiological research on the startle response is a linear trend corresponding to a relative decrease (or attenuation) of the startle response when attending to a pleasant stimulus, and a relative increase (or potentiation) of the startle response when attending to an unpleasant stimulus, as compared to a neutral stimulus (Bradley et al., 1999; Lang et al., 1990; Vrana, Spence, & Lang, 1988). This affective modulation of the startle response reflects not only the motivational system that is activated (the defensive system) by the startle probe itself but also the motivational system that is activated by the affective valence of the stimulus being attended to at the time the startle probe is presented. A startle probe is, by definition, an unpleasant stimulus intended to evoke a sudden response from the defensive system. According to the affective-match hypothesis (Lang et al., 1990), if the affective valence of the stimulus that is being attended to (i.e., the foreground stimulus) matches that of the startle probe (i.e., unpleasant), the startle response elicited by that probe will be relatively augmented. Relative inhibition of the startle reflex occurs during an affective mismatch; that is, if the foreground stimulus is pleasant during the presentation of an unpleasant startle probe. For example, if a person is already reacting to an unpleasant stimulus, such as a horror movie, the reflex elicited by the presentation of a sudden burst of noise will be greater than if the person were reacting to a pleasant stimulus, such as a comedy film, at the moment of startle probe

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6 presentation. Affective modulation of the startle reflex is not, however, limited to the acoustic startle probe modality. Startle Probe Modality Various probes are used in psychophysiological research to elicit the startle response from human participants, including acoustic (e.g., bursts of white noise) (Lipp et al., 2003; Vrana, 1994), visual (e.g., flashes of bright light) (Bradley et al., 2000), and tactile (e.g., air puffs) (Hawk & Cook, 1997). Individual differences in startle reflex magnitude are found to be stable across startle probe modalities, in that people who respond with relatively large startle reflexes to an acoustic startle probe also respond with relatively large startle reflexes to a visual startle probe (Bradley et al., 2000). Previous research finds that startle responses elicited by an acoustic probe are consistently larger than responses elicited by a visual probe. This difference has been attributed to differences in probe intensity as opposed to differences in modality (Bradley et al., 2000). Regardless of the rated aversiveness of the probe, affective modulation of the startle response is consistently shown regardless of the modality of the startle probe, with larger reflexes elicited when viewing unpleasant compared to pleasant pictures (Bradley et al., 2000; Lang, Bradley, & Cuthbert, 1990). Ethnic Differences in Physiology As previously mentioned, studies have shown ethnic differences in the perceived appropriateness (Matsumoto, 1990), display (Ekman, 1971; Friesen, 1972, as cited by Matsumoto, 1993), and subjective experience (Scherer et al., 1988; Matsumoto et al., 1988) of emotion. In addition, there is an extant literature revealing ethnic differences in physiological responding, specifically between African Americans and European Americans. Studies show that African Americans have lower skin conductance levels

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7 than European Americans (Bernstein, 1965; Johnson & Corah, 1963; Johnson & Landon, 1965; Juniper & Dykman, 1967; Malmo, 1965) and also higher rates of hypertension (Adams, 1932; Anderson, 1989; Haffner et al., 1990; Pappas, Gergen, & Carroll, 1990; Winkleby, Fortmann, & Rockhill, 1993). Recently, Brown, Bradley, and Lang (2002) found ethnic differences in the startle response to an acoustic probe. The results of Brown et al. (2002) showed an ethnic difference in startle magnitude (size of the startle response averaged across all trials, including those trials where no startle occurs) as well as the probability of a startle response. However, their data showed no ethnic difference in the size of the startle response averaged across only those trials where a startle occurs (amplitude) or in affective modulation (the standard valence effect occurs for each ethnic group). Thus, when a startle response did occur, there was no difference in the size of the response between African Americans and European Americans; however, African Americans startled less often than European Americans in response to an acoustic startle probe. Rationale for Current Study The startle reflex is a useful tool for studying emotion. As mentioned above, studies show that startle responses are consistent across probe modalities (i.e., people who exhibit a relatively large startle response to an acoustic probe also exhibit a relatively large response to a visual startle probe) (Bradley et al., 2000). Also, affective modulation occurs across startle probe modalities (Bradley et al., 2000; Lang et al., 1990). Although previous research finds systematic differences in a number of physiological measures between different ethnic groups, a recent search of PsycInfo and PubMed resulted in no entries pertaining to the investigation of ethnic differences in the startle response. Based on the lack of entries in the literature, researchers appear to study

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8 the startle reflex without addressing possible differences between ethnic groups. This oversight may be problematic, especially for researchers collecting data from an ethnically diverse sample. Systematic differences between ethnic groups in startle may confound results if not properly taken into consideration. Recent findings of Brown et al. (2002) showing ethnic differences in startle reflex probability and magnitude between African Americans and European Americans in response to an acoustic startle probe beg the question of why these differences occur. One possible explanation is a difference in hearing between ethnic groups. Research suggests that African Americans are less likely than European Americans to recognize the symptoms and risks associated with excessive noise exposure (Crandell, Mills, & Gauthier, 2004), and thus may be more likely to engage in behaviors that might lead to hearing impairment. A classic sign of noise induced hearing loss is a permanent decrease in hearing sensitivity in the frequency range of 3000-6000Hz (Henderson, Hamernik, Dosanjh et al., as cited by Crandell et al., 2004). Because this is the frequency range of the typical acoustic startle probe, hearing differences may account for differences in startle reflex probability and magnitude, in that African Americans may be less sensitive to an acoustic startle probe compared to European Americans. In addition to why the ethnic difference occurs, the replicability of the effect, the generalizability of the effect to other startle probe modalities, and the generalizability of the startle reflex as an indicator of emotion across ethnic groups (and across startle probe modalities) require further examination. Research Question The current study attempts to answer the following questions: 1) Are the ethnic differences previously found by Brown et al. (2002) in the probability and magnitude of

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9 the startle response specific to the acoustic startle probe modality or the results of more general ethnic differences in defensive responding? 2) Does affective modulation of startle reflex magnitude occur for African American as well as European American participants in response to both acoustic and visual startle probes? Hypotheses Ethnic Differences in Startle If the ethnic differences in startle probability and magnitude in response to an acoustic startle probe found by Brown et al. (2002) are specific to the auditory modality (e.g., due to hearing differences), ethnic differences in the startle reflex are expected in response to an acoustic startle probe but not in response to a visual startle probe. However, if the previously found ethnic differences are indicative of more general ethnic differences in basic defensive responding, ethnic differences are expected in startle reflexes elicited by both an acoustic and a visual startle probe. Affective Modulation Based on previous research examining affective modulation in response to startle probes presented through different modalities (e.g., acoustic and visual), replication of the standard affective modulation effect on startle magnitude is expected for both an acoustic and a visual startle probe for both European Americans and African Americans.

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CHAPTER 2 METHOD Participants Participants were 16 African American (9 female and 7 male) and 16 European American (7 female and 9 male) Introductory Psychology students at the University of Florida. One European American female was paid for her participation in the study while all other students received partial course credit for their participation. The mean age of participants was 18.91 years and all of the students were between 18 and 21 years of age. Materials and Design Stimuli The International Affective Picture System (or IAPS) is a standardized collection of over 700 pictures selected as affect-inducing stimuli (Lang, Bradley, & Cuthbert, 2001). Research shows that the IAPS serves this purpose well, providing photographic images that produce the desired range of emotional reactions, with varying degrees of intensity (Lang et al., 1993). The IAPS contains photographs depicting people, animals, nature, and objects, previously rated for valence (i.e., degree of pleasantness or unpleasantness) and arousal (i.e., intensity of activation). Thirty-six pictures were selected from the IAPS (Lang et al., 2001) for the current study. Pictures were chosen, based on their standardized ratings, to represent three affective valence categories (i.e., pleasant, neutral, unpleasant). The pleasant category was comprised of erotic pictures, including pictures of heterosexual couples and other (i.e., opposite) sex nudes. Neutral pictures included both indoor and outdoor scenes or 10

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11 objects. The unpleasant category consisted of pictures depicting physical threat, including attacking animals and attacking humans. Each of the three valence categories included 12 different pictures. 1 Two different orders of picture presentation were constructed to control for possible effects resulting from viewing pictures in a particular sequence. Each order was arranged in blocks of six, such that there were two exemplars from each of the three stimulus valence categories in each block of six, resulting in one picture from each content category in each block. That is, each block of six pictures contained two erotic pictures (one couple and one other sex nude), two neutral pictures (one inside and one outside neutral scene or object), and two unpleasant threat pictures (one animal attack and one human attack). Each order included identical pictures; however, arrangement occurred so that pictures would not immediately precede or follow the same pictures across blocks. Within each order, the other sex nudes were either of females (viewed by male participants) or of males (viewed by female participants), providing a total of four different picture combinations (i.e., order 1 for males, order 1 for females, order 2 for males, order 2 for females). Each participant was presented with only one picture order. Digitized versions of the IAPS pictures were projected by an LCD projector onto a large (70 x 56) screen, which was positioned approximately 6 feet in front the participant. Picture onset was nearly instantaneous, and each picture was presented for 6 seconds. Between each picture presentation (i.e., trial), an inter-trial interval (ITI) period (ranging 1 IAPS numbers used in this study were: Pleasant: 4002, 4669, 4290, 4652, 4687, 4220, 4310, 4611, 4180, 4658, 4250, 4672 (pictures 4002, 4290, 4220, 4310, 4180, 4250 were erotic pictures of females shown to male participants; pictures 4531, 4520, 4534, 4536, 4533, 4535 were erotic male pictures shown to female participants); Neutral: 7710, 5950, 7283, 5900, 7490, 5500, 7207, 5731, 7170, 5740, 5920, 7237; Unpleasant: 6212, 1050, 1220, 6350, 6313, 1270, 6243, 1280, 1301, 6230, 1930, 6570.

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12 in length from 8s to 16s) occurred when the screen was blank. All pictures were displayed in 32-bit color. Startle Probes The acoustic startle probe consisted of a 50-ms, 95dB burst of white noise, produce by a Coulbourn S81-02 white-noise generator. The stimulus was then gated through a Coulbourn S82-24 amplifier and presented to the participant over TDH-49 headphones. The headphones covered both ears of the participant, providing equal noise intensity to both ears. The visual startle stimulus consisted of a flash of light generated by the simultaneous firing of three professional photography flashguns. The three flashguns were positioned approximately 6 ft in front of the participant, and were not directed toward the participant. The startle probe was presented between 2.5 and 3.5s after each picture onset, as well as during 14 of the inter-trial intervals. During picture viewing, 18 acoustic startle probes were presented (6 per valence) and 18 visual startle probes were presented (6 per valence). Within each block of six pictures, three acoustic and three visual startle probes occurred. Either an acoustic or a visual startle probe was presented during each picture, with the constraint that if an acoustic probe was presented during a particular picture in order 1, a visual probe was presented during that same picture in order 2 (and vice versa). Participants received a total of seven acoustic and seven visual startle probes during inter-trial intervals. Hearing Test To examine hearing differences as a possible explanation for the ethnic differences found by Brown et al. (2002), a hearing test was conducted on each participant using a GSI-17 Audiometer (Grason-Stadler, Inc., Madison, WI). Participants hearing

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13 thresholds were measured in decibels (dB) for 10 different frequencies ranging from 250 Hz-8000 Hz. Questionnaires A pre-experimental questionnaire, comprised of the Personal Need for Structure Scale (Thompson, Naccarato, & Parker, 1989, as cited in Neuberg & Newsom, 1993) and the Interaction and Audience Anxiousness Scale (Leary, 1983) was completed by all participants (see Appendixes A and B, respectively). However, these measures were not relevant to the current investigation and are not mentioned further. A post-experimental questionnaire (see Appendix C), including basic demographic questions and items assessing the participants subjective experience, was administered at the conclusion of the experimental session. Of specific interest to the current study were items assessing the pleasantness of the startle probes. Items asked participants to rate the pleasantness of noises heard over headphones while watching pictures during the course of the experiment and to rate the pleasantness of flashes of light seen while watching pictures during the course of the experiment. Each of these items was scored on a 7-point scale, 1 = unpleasant, 7 = pleasant. All questionnaires are included in the Appendix. Startle Eyeblink Measurement and Reduction The eyeblink component of the startle response was measured by placing two 4mm In Vivo Metric (Healdsburg, CA) miniature electrodes over the inferior orbicularis oculi, using the placement recommended by Fridlund and Cacioppo (1986). Physiological data were acquired using an IBM-compatible computer running VPM version 11.2 data acquisition and reduction software (Cook, 2000). The raw electromyography (EMG) signal was amplified (x30,000), and frequencies below 90 Hz and above 250 Hz were filtered with a Coulbourn S75-01 bioamplifier. The raw signal was rectified and

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14 integrated with a Coulbourn S76-01 contour-following integrator, with a time constant of 200ms. Activity in the orbicularis oculi muscle was sampled at 20 Hz during baseline and picture viewing, with an increase in sampling rate to 1,000 Hz for 50 ms before the onset of the startle probe and for 250 ms after probe onset. The eyeblink data were reduced off-line by using a program that scored each trial for magnitude in analog-to-digital (A/D) units, using an algorithm devised by Globisch, Hamm, Schneider, and Vaitl (1993). Corrugator (frowning muscle) EMG activity was also measured in the experimental sessions but is not relevant to the current hypotheses and therefore is not reported. Procedure Participants were run individually. Participants sat in a recliner in a 9 x 13 dimly lit room. After providing informed consent and completing the pre-experimental questionnaire, a brief hearing test was administered. Participants were notified that a set of earphones would be placed over their ears and a variety of tones would be heard. They were instructed, in accordance with the instruction manual accompanying the GSI-17 Audiometer, to indicate when a tone was heard by raising the hand corresponding to the ear in which the tone was heard, and then lowering the hand when the tone was no longer heard. Participants were familiarized with the tone by receiving a sample tone at 1000 Hz and 40 dB. Hearing threshold was determined by presenting the tone for 1-2 seconds and increasing the volume level by 5 dB after each failure of the participant to respond. The threshold is the minimum volume setting at which the participant indicates that the tone is audible. The setting level (in dB) was then recorded as the hearing threshold. The testing procedure was repeated for each tone frequency setting, 250 Hz, 500 Hz, 1000 Hz,

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15 1500 Hz, 2000 Hz, 3000 Hz, 4000 Hz, 6000 Hz, and 8000 Hz, for the left ear and then for the right ear. Participants were then prepared for physiological recording. The skin under the eye was cleansed with water and a tissue to remove any makeup, oil, etc. that might impede the electrical signal. Electrolyte gel was placed inside the electrode cups as well as gently rubbed on the skin of the participant. Electrodes were then placed on the participant. Participants were instructed to attend to each picture throughout its duration and to remain as still as possible. A set of headphones was placed over the participants ears and was worn throughout the picture-viewing period to provide a channel for administering the acoustic startle probe. The lighting was dimmed, the door closed, and the participant was alone while viewing the pictures. The picture viewing session lasted approximately 17 minutes, after which the electrodes were removed from the participant and a post-experimental questionnaire was administered. Participants were subsequently debriefed, thanked for their participation, and dismissed. Analyses Analyses were conducted to assess effects of startle probe modality, picture valence, and ethnicity on magnitude, probability, and amplitude of the startle response. A 2 (startle probe modality: acoustic, visual) X 3 (picture valence: pleasant, neutral, unpleasant) X 2 (ethnicity: African American, European American) mixed-model ANOVA was conducted in which startle probe modality and picture valence were within subject factors and ethnicity was a between subjects factor. Because only those startle responses occurring while pictures were presented were of interest, startles occurring during inter-trial intervals were not analyzed. In cases where a significant effect of affective valence occurred, pairwise comparisons were subsequently conducted to

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16 determine the pattern of differences between the three levels (pleasant, neutral, unpleasant). All pairwise analyses were Bonferroni corrected for multiple comparisons. Based on the recommendations of Vasey and Thayer (1987) regarding within subject psychophysiological data, the multivariate Wilks Lambda test statistic is reported for all analyses including within subject variables. All means for magnitude and amplitude are reported in A/D units. All means for probability are expressed as a ratio of the number of trials during which a startle response occurred divided by the total number of trials. Data from three participants were excluded from analyses including startle probe modality as a factor due to startle responses that could not be used. Fourteen participants were excluded from analyses involving startle amplitude due to either startle responses that could not be used or lack of a startle response. Startle responses were determined to be unusable if the onset of the eyeblink occurred longer than 150ms after the presentation of the startle probe. Effects of participant ethnicity on hearing threshold were assessed by conducting a mixed-model analysis of variance (ANOVA), with participant ethnicity as a between subjects factor and tone frequency as a within subject factor. Because only the higher frequencies (3000, 4000, 6000, and 8000 Hz) are pertinent to the acoustic startle response (W. K. Berg, personal communication, January, 2004), only analyses involving these frequencies are reported.

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CHAPTER 3 RESULTS Magnitude Probe Modality Consistent with the results of previous studies (e.g., Bradley et al., 2000), startle magnitude was affected by the modality of the startle probe, F (1, 27) = 14.10, p = .001, eta-squared = .343, in that a response elicited by an acoustic probe (M = 180.52, SD = 199.14) was greater than one elicited by a visual probe (M = 56.39, SD = 73.88). Valence The magnitude of the startle reflex was modulated by the affective valence of the picture stimulus, F (2, 26) = 7.60, p < .01, eta-squared = .369. The size of the startle response was different depending on whether the participant was viewing a pleasant picture, neutral picture, or unpleasant picture at the time the startle probe was presented. Picture valence and startle probe modality interacted to produce an effect on startle magnitude, F (2, 26) = 3.66, p < .05, eta-squared = .220. The nature of this interaction was examined more closely by analyzing the effect of picture valence on startle magnitude separately for acoustic and visual startle probes. Replicating previous findings, results revealed a significant effect of picture valence on blink magnitude for the acoustic startle probe, F (2, 30) = 6.83, p < .005, eta-squared = .313. Figure 3-1 (top panel) illustrates the pattern of startle reflex magnitude obtained in response to an acoustic startle probe while viewing affective pictures. 17

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18 100120140160180200Startle Magnitude (A/D Units) PleasantNeutralUnpleasant Acoustic Startle Probe 40506070Startle Magnitude (A/D Units) PleasantNeutralUnpleasant Visual Startle Probe Figure 3-1. Top panel: Startle blink magnitude when elicited by an acoustic startle probe, while viewing pleasant, neutral, or unpleasant pictures. Bottom panel: Startle blink magnitude when elicited by a visual startle probe, while viewing pleasant, neutral, or unpleasant pictures. Planned pairwise analyses revealed that larger blinks were elicited by an acoustic probe when viewing unpleasant (M = 192.36, SD = 199.98) compared to pleasant (M =

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19 136.09, SD = 173.68) pictures, p < .01, and smaller blinks were elicited when viewing pleasant (M = 136.09, SD = 173.68) compared to neutral (M = 190.30, SD = 204.68) pictures, p < .01. No difference in blink magnitude was found when viewing neutral (M = 190.30, SD = 204.68) compared to unpleasant (M = 192.36, SD = 199.98) pictures, p = ns, when elicited by an acoustic probe. Results also revealed a significant effect of picture valence on blink magnitude for the visual startle probe, F (2, 27) = 4.11, p < .05, eta-squared = .233. Figure 3-1 (bottom panel) illustrates the pattern of startle reflex magnitude obtained in response to a visual startle probe. Planned pairwise comparisons revealed that larger blinks were elicited when viewing unpleasant (M = 63.84, SD = 75.49) compared to pleasant (M = 49.28, SD = 67.33) pictures, p < .05. No differences in blink magnitude were found when viewing pleasant (M = 49.28, SD = 67.33) compared to neutral (M = 57.70, SD = 87.43) pictures, p = ns, or when viewing neutral (M = 57.70, SD = 87.43) compared to unpleasant (M = 63.84, SD = 75.49) pictures, p = ns. Ethnicity In contrast to results found by Brown et al. (2002), the magnitude of the startle response did not differ between African American participants (M = 120.45, SD = 168.10) and European American participants (M = 116.45, SD = 174.00), F (1, 27) < 1, p = ns, eta-squared = .000. Ethnicity did not interact with picture valence, F (2, 26) = 1.19, p = ns, eta-squared = .084, or startle probe modality, F (1, 27) <1, p = ns, eta-squared = .026, to affect startle magnitude. The three way interaction between picture valence, startle probe modality, and ethnicity was also not significant for startle magnitude, F (2, 26) = 1.24, p = ns, eta-squared = .087. Thus, the ethnicity of the participant did not affect the pattern of affective modulation obtained in response to either an acoustic or a visual

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20 startle probe. Figure 3-2 illustrates the patterns of startle reflex magnitude obtained from European American and African American participants in response to acoustic (top panel) and visual (bottom panel) startle probes. 100120140160180200220Startle Magnitude (A/D Units) Eur AmAfr Am Pleasant Neutral Unpleasant Acoustic Startle Probe 020406080Startle Magnitude (A/D Units) Eur AmAfr Am Pleasant Neutral Unpleasant Visual Startle Probe Figure 3-2. Startle blink magnitude obtained from European American and African American participants in response to acoustic (top panel) and visual (bottom panel) startle probes.

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21 Probability Probe Modality Replicating previous studies, the probability of a startle response was significantly affected by startle probe modality, F (1, 27) = 19.42, p < .001, eta-squared = .418. The likelihood of an occurrence of a startle response elicited by an acoustic probe (M = .77, SD = .30) was greater than the likelihood of an occurrence of a startle response elicited by a visual probe (M = .46, SD = .35). Valence The picture valence affected the probability of an occurrence of a startle response, F (2, 26) = 3.26, p = .05, eta-squared = .201. Figure 3-3 depicts the pattern of startle response probability obtained while viewing affective pictures. Pairwise comparisons revealed that the likelihood of a startle response was greater when viewing unpleasant (M = .66, SD = .26), compared to pleasant (M = .58, SD = .30) pictures, p < .05. No differences occurred, in terms of probability, between startles elicited while viewing pleasant pictures (M = .59, SD =.29) compared to neutral pictures (M = .60, SD = .27), p = ns, or neutral pictures (M = .60, SD = .27) compared to unpleasant pictures (M = .66, SD = .26), p = ns Startle probe modality and picture valence did not interact to produce an effect on startle response probability, F (2, 26) = 2.71, p = ns, eta-squared = .172.

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22 0.50.550.60.650.7Probability of a Startle Response PleasantNeutralUnpleasant Figure 3-3. The probability of a startle response, averaged across acoustic and visual startle probe modalities, while viewing pleasant, neutral, or unpleasant pictures. Ethnicity Results did not show a significant difference between African American participants (M = .611, SD = .37) and European American participants (M = .614, SD = .38) in the probability of a startle response, F (1, 27) < 1, p = ns, eta-squared = .000. Participant ethnicity did not interact with picture valence, F (2, 26) < 1, p = ns, eta-squared = .053, or probe modality, F (1, 27) < 1, p = ns, eta-squared = .028, to affect the probability of a startle response. The three-way interaction between picture valence, probe modality, and participant ethnicity was also not significant for probability, F (2, 26) < 1, p = ns, eta-squared = .067.

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23 Amplitude Recall that startle amplitude is calculated by averaging startle size over trials where a startle response occurred. Thus, amplitude is an indication of startle size, controlling for probability. Probe Modality The modality of the startle probe affected the amplitude of the startle response, F (1, 16) = 9.55, p < .01, eta-squared = .374. Eye-blinks elicited by acoustic startle probes were larger (M = 254.27, SD = 212.73) than those elicited by visual startle probes (M = 108.97, SD = 69.15). Valence The affective valence of the picture stimulus significantly affected the amplitude of the startle response, F (2, 15) = 6.94, p < .01, eta-squared = .481. Figure 3-4 illustrates the pattern of startle reflex amplitude, across startle probes, obtained while viewing affective pictures. Pairwise analyses revealed larger blinks were elicited while viewing unpleasant (M = 194.15, SD = 127.42) compared with pleasant (M = 150.04, SD = 114.59) pictures, p < .01. Smaller blinks were elicited while viewing pleasant (M = 150.04, SD = 114.59) compared with neutral (M = 200.67, SD = 134.89) pictures, p < .01. Startle responses while viewing neutral pictures (M = 200.67, SD = 134.89) did not differ in amplitude compared with responses while viewing unpleasant (M = 194.15, SD = 127.42) pictures, p = ns Picture valence and startle probe modality did not interact to affect startle amplitude, F (2, 15) = 2.71, p = ns, eta-squared = .266.

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24 100120140160180200220Startle Amplitude (A/D Units) PleasantNeutralUnpleasant Figure 3-4. Startle blink amplitude, averaged across acoustic and visual startle probe modalities, while viewing pleasant, neutral, or unpleasant pictures. Ethnicity African American participants (M = 196.61, SD = 122.76) and European American participants (M = 166.63, SD = 122.76) did not differ in startle amplitude, F (1, 16) < 1, p = n.s, eta-squared = .017. Participant ethnicity did not interact with picture valence, F (2, 15) = 2.72, p = ns, eta-squared = .266, or probe modality, F (1, 16) < 1, p = ns, eta-squared = .005, to affect startle amplitude. The three-way interaction between picture valence, probe modality, and participant ethnicity was also not significant for amplitude, F (2, 32) < 1, p = ns, eta-squared = .042. Tests of Alternative Explanations Hearing Because the acoustic startle probe was presented through headphones to both the left and right ears simultaneously, the hearing data were averaged across both ears. Results showed that ethnicity had no effect on hearing threshold, F (1, 30) < 1, p = ns,

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25 eta-squared = .016. The average decibel level at which a tone in the frequency range of 3000-8000 Hz was audible (i.e., hearing threshold) was not significantly different between African American (M = 7.89, SD = 4.17) and European American (M = 7.58, SD = 4.17) participants. Mean hearing thresholds for each ethnic group at each frequency level are reported in Figure 3-5. 024681012141618Hearing Threshold in dB 2505007501000150020003000400060008000Frequency Eur Am Afr Am Figure 3-5. Mean hearing thresholds for each ethnic group at each frequency level. Subjective Ratings of Startle Probes A 2 (startle probe modality: acoustic, visual) X 2 (ethnicity: African American, European American) mixed-model ANOVA was conducted on the subjective ratings of the pleasantness of the startle probes, with startle probe modality as a within subjects factor and participant ethnicity as a between subjects factor. Results revealed that acoustic startle probes (M = 2.16, SD = .88) were consistently rated as more unpleasant than visual startle probes (M = 3.00, SD = 1.05), F (1, 30) = 16.01, p< .0001, eta-squared = .348. In addition, African Americans (M = 2.31, SD = .72) rated the startle probes in

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26 general as more unpleasant, compared with European Americans (M = 2.84, SD = .72), F (1, 30) = 4.29, p < .05, eta-squared = .125. Probe modality and participant ethnicity did not interact to affect subjective ratings of the startle probes, F (1, 30) = 1.08, p = ns, eta-squared = .035.

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CHAPTER 4 DISCUSSION It was hypothesized that if the ethnic differences in probability and magnitude previously found by Brown et al. (2002) were due to general ethnic differences in defensive responding, their results would be replicated in response to an acoustic as well as a visual startle probe. If, however, the ethnic differences previously found by Brown et al. were somehow specific to an acoustic startle probe (perhaps due to hearing differences), replication of the previously found results with an acoustic startle probe but not with a visual probe was expected. In contrast to expectations, the current study did not show any ethnic differences in the startle response in terms of magnitude, probability, or amplitude. Not only did no ethnic differences occur in the startle reflex in response to a visual probe, but replication of Brown et al., (2002) of ethnic differences in probability and magnitude was also not attained in response to an acoustic probe. One possible explanation for the ethnic differences in startle found by Brown et al. (2002) is a difference in hearing between the two ethnic groups. For an acoustic startle probe to be effective, it must be heard. Thus, the quality of auditory processing might affect the probability and size of the startle response. Individuals with optimal auditory processing capability would likely exhibit a greater probability of startle as well as enhanced startle size compared to individuals with suboptimal auditory processing capability. However, results showed no difference in ability to hear between African American and European American participants, suggesting that differences in hearing did not contribute to the differences in acoustically elicited startle previously found by Brown 27

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28 et al. (2002). The failure to replicate previously found ethnic differences in response to an acoustic startle probe initiates the exploration of possible explanations that may account for the incongruity of results. If one ethnic group rated the startle probes as more unpleasant compared to the ratings of the other ethnic group (indicating a more aversive experience), differences in the size and/or probability of a startle response may be attributable to differences in subjective experience. African American participants did, in fact, indicate that the startle probes were more unpleasant than the European American participants did; however, results showed no ethnic differences in actual startle size or probability. Moreover, the ethnic difference in subjective ratings does not offer an explanation for the findings of Brown et al. (2002). The current study found that African American participants, compared with European American participants, found the startle probes to be more unpleasant. If subjective experience directly affected the startle response, it would be expected that African American participants would actually exhibit greater startle probability and enhanced startle size compared to European Americans. However, the direction of means of the subjective ratings is counter to what would be expected if subjective experience directly affected the startle response. There are differences that exist between the Brown et al. (2002) study and the current study that may be offered as possible explanations for the incongruity of the results regarding ethnic differences in the probability and magnitude of startle. First, the picture sets were different. Although both sets of pictures are from the IAPS collection and both include pictures representing pleasant, neutral, and unpleasant valences, picture content was not identical in the two studies. For example, almost two thirds of the

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29 pictures in the Brown et al. study were of people, and included depictions of mutilated bodies in addition to threat in the unpleasant valence category. Only half of the pictures in the current study depicts people (the other half is comprised of animals, objects, and scenes), and the unpleasant valence category does not include any depictions of mutilated bodies, but only threat. The current study attempted to replicate previously found ethnic differences in startle reflex magnitude and probability in response to an acoustic probe and investigate whether ethnic differences extend to another startle probe modality. Therefore, the picture set used was similar to the picture set utilized by Bradley et al. (2000) in their study revealing the stability of individual differences in startle response size across startle probe modalities. Future research is needed to investigate the possible effects of specific picture content on ethnic differences in startle. Specifically, an investigation of ethnic differences in the startle response across probe modalities utilizing the stimulus picture set from the Brown et al. study may be helpful in shedding light on whether ethnic differences in startle are dependent on specific picture stimuli. Second, the ethnicity of the experimenter(s) is different. In the Brown et al. (2002) study, some participants interacted with both an African American and a European American female experimenter, while others interacted with either an African American or a European American female experimenter. In the current study, participants interacted only with a European American female experimenter. Because participant ethnicity was examined as a source of possible differences, it seems possible that the ethnicity of the experimenter might also affect the participants reactions. The effect of the experimenters ethnicity, however, was examined in the Brown et al. study

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30 and did not have any effect on participants startle response. Therefore, the difference in experimenter ethnicity seems an unlikely explanation for the inconsistent findings. Third, the sample is different. In addition to the sample in the Brown et al. (2002) study being over two and half times larger than that of the current study, it is possible that only a subpopulation of African Americans exhibit decreased startle probability and magnitude compared to European Americans. Research investigating the startle reflex in animal samples in response to an acoustic startle probe has found differences in startle size among inbred strains of mice (Willott et al., 2003) and rats (Conti & Printz, 2003). In addition, differences in startle magnitude have been found in rats with predispositions for different types of defensive behavior (e.g., passive freezing responses, aggressive behavior) (Popova et al., 2000). Together, these results suggest that responsiveness to a startle probe may be influenced by a genetic component. Thus, it is possible that a subpopulation of African Americans display the pattern of startle response found by Brown et al. (i.e., decrease in startle response probability and magnitude), but members of that subpopulation were not included in adequate number in the current sample. According to the motivational priming organization proposed by Lang et al. (1998), situations that promote survival (e.g., copulation) prime the activation of the appetitive system, whereas situations involving threat (e.g., attack) prime the activation of the defensive system. The motivational priming organization predicts that startle reflex size will be enhanced when the foreground stimulus (e.g., a picture) is unpleasant and inhibited when the foreground stimulus is pleasant. In addition, the affective match hypothesis proposed by Lang et al. (1990) proposes that the differentiation in startle reflex size is based on whether the affective valence of the stimulus is matched or

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31 mismatched with the affective valence of the startle probe. This position suggests that affective modulation of the startle response is dependent on the affective match or mismatch of the stimulus and the startle probe, not the modality of the probe itself. Thus, affective modulation should occur regardless of whether the startle probe is acoustic or visual. Based on the motivational priming organization and the affective match hypothesis, it was expected that affective modulation would occur for a visual as well as an acoustic startle probe. Due to the recently obtained ethnic differences in startle probability and magnitude, it was deemed prudent to systematically test for ethnic differences in affective modulation. However, because there was no explicit reason to believe that ethnic differences would occur, it was predicted that affective modulation would occur for both ethnic groups. As expected, replication of the standard affective modulation effect for both ethnic groups and for both startle probe modalities was attained, with larger startle reflex magnitude elicited when viewing unpleasant, compared to pleasant, pictures. Because startle magnitude is an indication of the emotional state of the individual at the time of the startle probe presentation, results suggest that the startle response is a reliable measure of emotion across ethnic groups.

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CHAPTER 5 CONCLUSION Until recently, researchers studying the startle response have not acknowledged the possibility of ethnic differences, or at least have not reported systematically testing for such differences. In light of the current findings, the possibility of ethnic differences in the startle response is still unclear and future research is needed to further investigate this line of study. Taken together, the current results suggest that the startle response is a reliable measure of emotion for both European Americans and African Americans whether elicited by an acoustic or a visual startle probe 32

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APPENDIX A PERSONAL NEED FOR STRUCTURE SCALE Read each of the following statements and decide how much you agree with each according to your attitudes, beliefs, and experiences. It is important for you to realize that there are no right or wrong answers to these questions. People are different, and we are interested in how you feel. Please respond according to the following 6-point scale. 1 = strongly disagree 2 = moderately disagree 3 = slightly disagree 4 = slightly agree 5 = moderately agree 6 = strongly agree ___ 1. It upsets me to go into a situation without knowing what I can expect from it. ___ 2. Im not bothered by things that interrupt my daily routine. ___ 3. I enjoy having a clear and structured mode of life. ___ 4. I like to have a place for everything and everything in its place. ___ 5. I enjoy being spontaneous. ___ 6. I find that a well-ordered life with regular hours makes my life tedious. ___ 7. I dont like situations that are uncertain. ___ 8. I hate to change my plans at the last minute. ___ 9. I have to be with people who are unpredictable. ___ 10. I find that a consistent routine enables me to enjoy life more. ___ 11. I enjoy the exhilaration of being in unpredictable situations. ___ 12. I become uncomfortable when the rules in a situation are not clear. 33

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APPENDIX B INTERACTION AND AUDIENCE ANXIOUSNESS SCALE For the next 15 items, read each of the following statements carefully and indicate how characteristic it is of you according to the following scale: 1 = Not at all characteristic of me. 2 = Slightly characteristic of me. 3 = Moderately characteristic of me. 4 = Very characteristic of me. 5 = Extremely characteristic of me. Please answer each question as accurately and honestly as you can. _____ 1. I often feel nervous in casual get-togethers. _____ 2. I usually feel uncomfortable when I'm in a group of people I don't know. _____ 3. I am usually at ease when speaking to a member of the opposite sex. _____ 4. I get nervous when I must talk to a teacher or a boss. _____ 5. Parties often make me feel anxious and uncomfortable. _____ 6. I am probably less shy in social interactions than most people. _____ 7. I sometimes feel tense when talking to people of my own sex if I don't know them very well. _____ 8. I would be nervous if I was being interviewed for a job. _____ 9. I wish I had more confidence in social situations. ____ 10. I seldom feel anxious in social situations. ____ 11. In general, I am a shy person. ____ 12. I often feel nervous when talking to an attractive member of the opposite sex. ____ 13. I often feel nervous when calling someone I don't know very well on the telephone. ____ 14. I get nervous when I speak to someone in a position of authority. ____ 15. I usually feel relaxed around other people, even people who are quite different from me. 34

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APPENDIX C POST-EXPERIMENTAL QUESTIONNAIRE Age: Date: Were you born in the U.S.? Yes No Year in school: Do you consider yourself an American? Yes No Gender (circle one): Female Male Sexual orientation: Bisexual Gay/Lesbian Heterosexual Ethnicity: Asian Biracial Black Hispanic White Other: ______________ Height: Weight: Handedness: Left Right Ambidextrous Are any of your biological relatives left-handed? Specify. Did you ever switch handedness preferences? If so, explain: If you are a woman, what are the approximate dates of your last menstrual period? Do you wear glasses or contact lenses? Yes No Were you wearing them during the experiment? Yes No Do you have hearing problems? Yes No If so, please describe: Do you have a chronic illness? Yes No If so, please explain: Do you have a current illness? Yes No If so, please explain: 35

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36 Do you take any special medication (for example, birth control pills, allergy medication, anti-anxiety medicine, anti-psychotic medicine, stress relievers)? Yes No If so, please explain: Are you currently on any form of over-the-counter medication (for example, aspirin, Tylenol, Advil, allergy medicine)? Yes No If so, please explain: Have you used any recreational drugs within the last 48 hours? Yes No If so, please specify: Is there any pre-existing state you are in which could have affected your response to the slides (for example, extreme excitement, sadness, happiness)? Do you get anxious in small spaces? Yes No Rate pleasantness of sensors under eyes: 1 2 3 4 5 6 7 UNPLEASANT PLEASANT Rate pleasantness of noises heard over headphones while watching pictures during the course of the experiment 1 2 3 4 5 6 7 UNPLEASANT PLEASANT Estimate the number of noises heard over the headphones during the course of the experiment: Rate confidence of this estimate 1 2 3 4 5 6 7 NOT VERY CONFIDENT VERY CONFIDENT Rate pleasantness of flashes of light seen while watching pictures during the course of the experiment 1 2 3 4 5 6 7 UNPLEASANT PLEASANT Estimate the number of flashes seen during the course of the experiment: Rate confidence of this estimate: 1 2 3 4 5 6 7

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37 NOT VERY CONFIDENT VERY CONFIDENT Was there any regularity in the pattern when noises were presented? Yes No If so, please explain: Was there any regularity in the pattern when flashes were presented? Yes No If so, please explain: Rate how much the noises over the headphones made you startle: 1 2 3 4 5 6 7 NOT VERY MUCH VERY MUCH Rate how much the flashes of light made you startle: 1 2 3 4 5 6 7 NOT VERY MUCH VERY MUCH What were you thinking about between picture presentations? Could you see the pictures on the screen? Yes No Please rate each of the following types of pictures in terms of how pleasant or unpleasant you found them. Use this scale 1= Very Unpleasant, 4 = Neutral, 7 = Very Pleasant Violence _______ Erotica ______ Household objects/scenes _______ Animals ______ Did you have trouble staying awake during the study? Yes No Did you fall asleep at any time during the study? Yes No What do you think was our hypothesis for this experiment? Please add any additional comments you have about any aspect of the laboratory, the experiment, or your experimenter:

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LIST OF REFERENCES Adams, J. M. (1932). Some racial differences in blood pressure and morbidity in groups of white and colored workmen. The American Journal of the Medical Science, 184, 342. Anderson, N. B. (1989). Racial differences in stress-induced cardiovascular reactivity and hypertension: Current status and substantive issues. Psychological Bulletin, 105, 89-105. Bernstein, A. S. (1965). Race and examiner as significant influences on basal skin impedance. Journal of Personality & Social Psychology, 1, 346-349. Bradley, M. M, Cuthbert, B. N., & Lang, P. J. (1999). Affect and the startle reflex. In M. E. Dawson, A. M. Schell, & A. H. Bohmelt (Eds.) Startle modification: Implications for neuroscience, cognitive science, and clinical science. Cambridge University Press. Bradley, M. M., & Lang, P. J. (2000). Measuring emotion: Behavior, feeling, and physiology. In R. Lane & L. Nadel (Eds),Cognitive Neuroscience of Emotion, Series in affective science. Oxford University Press, New York, NY. p. 242-276. Bradley, M. M., Safi, F., Soler-Baillo, J., & Lang, P. J. (2000, October). Startle modality and size: Is a big startler always a big startler? Poster presented at the 40 th meeting of the Society for Psychophysiological Research, San Diego, CA. Brown, L. M., Bradley, M. M., & Lang, P. J. (2002, October). The role of ethnicity in affective reactions to ingroup and outgroup pictures. Presented at a symposium entitled What Has Psychophysiology Revealed About Ethnicity and Emotion? chaired by Jeanne L. Tsai at the 42 nd meeting of the Society for Psychophysiological Research, Washington, DC. Conti, L. H., & Printz, M. P. (2003). Rat strain-dependent effects of repeated stress on the acoustic startle response. Behavioural Brain Research, 144, 11-18. Cook, E. W., III. (2000). VPM reference manual. Birmingham, AL: Author. Crandell, C., Mills, T. L., & Gauthier, R. (2004). Knowledge, behaviors, and attitudes about hearing loss and hearing protection among racial/ethnically diverse young adults. Journal of the National Medical Association, 96, 176-185 38

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39 Davis, M. & Lang, P. J. (2003). Emotion. In M. Gallagher & R. J. Nelson (Eds.), Handbook of psychology: Vol. 3. Biological psychology. New York: Wiley. Dickinson, A. & Dearing M. F. (1979) Appetitive-aversive interactions and inhibitory processes. In A. Dickinson & R. A. Boakes (Eds) Mechanisms of Learning and Motivation. Hillside, NJ, Erlbaum, pp 203-231. Ekman, P. (1971). Universals and cultural differences in facial expressions of emotion. In J. Cole (Ed.), Nebraska Symposium on Motivation. Lincoln: University of Nebraska Press. Fridlund, A. J., & Cacioppo, J. T. (1986). Guidelines for human electromyographic research. Psychophysiology, 23, 567-589. Frijda, N. H. (1986). The emotions. New York: Cambridge University Press. Globisch, J., Hamm, A., Schneider, R., & Vaitl, D. (1993). A computer program for scoring reflex eyeblink and electrodermal responses written in Pascal. Psychophysiology, 39, S30. Haffner, S. M., Mitchell, B. D., Stern, M. P., Hazuda, H. P., & Patterson, J. K. (1990). Decreased prevalence of hypertension in Mexican-Americans. Hypertension, 16, 225-34. Hawk, L. W. & Cook, E. W. (1997). Affective modulation of tactile startle. Psychophysiology, 34, 23-31. Hunt, W. A., & Clarke, F. M. (1937). The startle pattern in children and identical twins. Journal of Experimental Psychology, 21, 359-362. Izard, C. (1977). Human emotions. New York: Plenum Press. Johnson, L. C. & Corah, N. L. (1963). Racial differences in skin resistance. Science, 139, 766-767. Johnson, L. C. & Landon, M. M. (1965). Eccrine sweat gland activity and racial differences in resting skin conductance. Psychophysiology, 1, 322-329. Juniper, K. & Dykman, R. A. (1967). Skin resistance, sweat gland counts, salivary flow and gastric secretion: Age, race, and sex differences, and intercorrelations. Psychophysiology, 4, 216-222. Konorski, J. (1967). Integrative activity of the brain: An interdisciplinary approach. Chicago: University of Chicago Press. Lang, P. J. (1993). The three system approach to emotion. In N. Birbaumer & A. Ohman (Eds), The Organization of Emotion (pp. 18-30). Toronto: Hogrefe-Huber.

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40 Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (1990). Emotion, attention, and the startle reflex. Psychological Review, 97, 377-395. Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (1998). Emotion, motivation, and anxiety: Brain mechanisms and psychophysiology. Biological Psychiatry, 44, 1248-1263. Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (2001). International affective picture system (IAPS). National Institutes of Mental Health (NIMH) Center for the Study of Emotion and Attention. University of Florida, Gainesville, FL. Lang, P. J., Greenwald, M. K., Bradley, M. M., Hamm, A. O. (1993) Looking at pictures: Affective, facial, visceral, and behavioral reactions. Psychophysiology, 30, 261-273. Leary, M. R. (1983). Social anxiousness: The construct and its measurement. Journal of Personality Assessment, 47, 66-75. Leary, M. R., Koch, E. J., & Hechenbleikner, N. R. (2001). Emotional responses to interpersonal rejection. In M. R. Leary (Ed.), Interpersonal Rejection (pp.145-166). New York: Oxford University Press. Lipp, O. V., Neumann, D. L., Pretorius, N. R., & McHugh, M. J. (2003). Attentional blink modulation during sustained and after discrete lead stimuli presented in three sensory modalities. Psychophysiology, 40, 285-290. Malmo, R. B. (1965). Physiological gradients and behavior. Psychological Bulletin, 64, 225-34. Matsumoto, D. (1990). Cultural similarities and differences in display rules. Motivation and Emotion, 14, 195-214. Matsumoto, D. (1993). Ethnic differences in affect intensity, emotion judgments, display rule attitudes, and self-reported emotional expression in an American sample. Motivation and Emotion, 17, 107-123. Matsumoto, D., Kudoh, T., Scherer, K., & Wallbott, H. (1988). Emotion antecedents and reactions in the U.S. and Japan. Journal of Cross-Cultural Psychology, 19, 267-286. Neuberg, S. L., & Newsom, J. T. (1993). Personal need for structure: Individual differences in the desire for simpler structure. Journal of Personality and Social Psychology, 65, 113-131. Pappas, P., Gergen, P. J., & Carroll, M. (1990). Hypertension prevalence and the status of awareness, treatment, and control in the Hispanic Health and Nutrition Examination Survey (HHANES), 1982-84. American Journal of Public Health, 80, 1431-1436.

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41 Popova, N. K., Barykina, N. N., Plyusnina, T. A., Alekhina, T. A., Kolpakov, V. G. (2000). Expression of the startle reaction in rats genetically predisposed towards different types of defensive behavior. Neuroscience and Behavioral Physiology, 30, 321-325. Scherer, K., Matsumoto, D., Wallbott, H., & Kudoh, T. (1988). Emotional experience in cultural context: A comparison between Europe, Japan, and the U.S.A. In K. Scherer (Ed.), Facets of emotion: Recent research. Hillsdale, NJ: Erlbaum. Vasey, M. W., & Thayer, J. F. (1987). The continuing problem of false positives in repeated measures ANOVA in psychophysiology: A multivariate solution. Psychophysiology, 24, 479-186. Vrana, S. R. (1994). Startle reflex response during sensory modality specific disgust, anger, and neutral imagery. Journal of Psychophysiology, 8, 211-218. Vrana, S. R., Spence, E. L., & Lang, P. J. (1988). The startle probe response: A new measure of emotion? Journal of Abnormal Psychology, 97, 487-491. Willott, J. F., Tanner, L., OSteen, J., Johnson, K. R., Bogue, M. A., & Gagnon, L. (2003). Acoustic startle and prepulse inhibition in 40 inbred strains of mice. Behavioral Neuroscience, 117, 716-727. Winkleby, M. A., Fortmann, S. P., & Rockhill, B. (1993). Health-related risk factors in a sample of Hispanics and whites matched on sociodemographic characteristics. The Stanford Five-City Project. American Journal of Epidemiology, 137, 1365-1375.

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BIOGRAPHICAL SKETCH Kathryn Gray was born on February 27, 1976, in Springfield, OH. She has been a resident of Florida since 1978, graduating from Palm Bay High School in Melbourne, FL, in 1994. In 1998, she earned a Bachelor of Science in psychology from the University of Central Florida in Orlando. After three and a half years of working in the real world, she decided to pursue graduate training and entered the social psychology program at the University of Florida. In 2004, she earned a Master of Science in psychology (specializing in social psychology) and a minor in research and evaluation methodology from the University of Florida. 42


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STARTLE PROBE MODALITY: AN INVESTIGATION OF ETHNIC DIFFERENCES


By

KATHRYN S. GRAY


















A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2004


































Copyright 2004

by

Kathryn S. Gray















ACKNOWLEDGMENTS

I thank my advisor, Lisa M. Brown, for her guidance, advice, and unbridled

enthusiasm for the field of social psychology and for life in general. I owe a great deal of

gratitude to Margaret Bradley, Peter Lang, and the NIMH Center for the Study of

Emotion and Attention for graciously allowing me to utilize their facilities. I thank my

committee members, Margaret Bradley, James Algina, and James Shepperd, for their

thoughtful comments and suggestions on this thesis.

I am forever grateful to my parents for a lifetime of support, encouragement, and

unconditional love. I thank Mike Bolen for listening, offering support, and being my best

friend.

I owe a deep appreciation to Mr. Kreinbihl, my 4th grade math teacher, who sparked

my interest in mathematics; Mr. Pekich, my 11th grade Chemistry II teacher, who

introduced me to the world of research and good science; my brother, Mark, who inspires

me in general, but who provided the foundation for my fascination with psychology; and

to people in general who not only prompted my interest in social psychology, but who

give me the opportunity to study and apply social psychology each day of my life.

















TABLE OF CONTENTS

page

A C K N O W L E D G M E N T S ................................................................................................. iii

LIST OF FIGURES ...... ............................... vi

ABSTRACT.................. .................. vii

CHAPTER

1 INTRODUCTION ................... .................. .............. .... ......... .......

Emotion ...................................... ................................... ........ .2
Startle .................................. ................................................3
Affect and Startle.................... ......................4
Startle Probe M odality................................................6
Ethnic D differences in Physiology ........................................................... ..............6
Rationale for Current Study......................................................... ........ .. ......7
Research Question ............................................... .............8
H ypotheses............... ... ..................................9
E thnic D differences in Startle ........................................................... ..............9
A effective M odulation .............................. ........................... ..9

2 METHOD ................................................... .........10

Participants ................................................10
M materials and D design .................. .......... .. ............ .... .... ... 10
Stimuli ................................................10
Startle Probes...................................... ........................................12
Hearing Test ................................................12
Q uestionnaires................. .................................................... .......13
Startle Eyeblink Measurement and Reduction .................................... ........13
Procedure ......................................................... ................. 14
A nalyses.................................................... 15

3 RESULTS ......................................................... ..........................17

Magnitude......................................................... ..........................17
Probe Modality ......................................................... ........... ........17
V alence ................... ........................................ ....... ........................... 17










Ethnicity .......................... .................... .........19
Probability...................................... .................. .............. ........ 21
Probe Modality ..................................................... ........21
V alence ...................................................................................... 21
Ethnicity ........................................ .........22
Amplitude ................................................... .........23
Probe Modality ..................................................... ........23
V alence ...................................................................................... 23
Ethnicity ............................................. .........24
Tests of Alternative Explanations....................................................................24
Hearing ..................................................24
Subjective Ratings of Startle Probes ......... ..............................25

4 DISCUSSION ........................ ......... .... ..........27

5 CONCLUSION.......................................... ........32

APPENDIX

A PERSONAL NEED FOR STRUCTURE SCALE ........................................33

B INTERACTION AND AUDIENCE ANXIOUSNESS SCALE............... ............34

C POST-EXPERIMENTAL QUESTIONNAIRE .............................. ...............35

LIST OF REFEREN CES ................................................... ........................ 38

BIOGRAPHICAL SKETCH .................................................. ........42


























v
















LIST OF FIGURES

Figure page

3-1 Startle blink m magnitude. ................................................. ......... 18

3-2 Startle blink magnitude obtained from European American and African American
participants .......................................................20

3-3 The probability of a startle response. ......................................... 22

3-4 Startle blink am plitude. ............................................... ............... 24

3-5 Mean hearing thresholds for each ethnic group at each frequency level. .............25
















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

STARTLE PROBE MODALITY: AN INVESTIGATION OF ETHNIC DIFFERENCES

By

Kathryn S. Gray

August 2004

Chair: Lisa M. Brown, Ph.D.
Major Department: Psychology

Ethnic differences in the startle response were assessed. Eyeblink reflexes for

European Americans and African Americans were examined in response to acoustic

(bursts of noise) and visual (flashes of light) startle probes while viewing 36 pictures

representing pleasant, neutral, or unpleasant content. An effect of picture valence was

obtained for both ethnic groups in response to both acoustic and visual startle probes.

The ethnic groups did not differ in startle reflex probability, magnitude, or amplitude.

Taken together, the results suggest that the startle response is a reliable measure of

emotion for European Americans and African Americans whether elicited by acoustic or

visual startle probes.














CHAPTER 1
INTRODUCTION

Imagine sitting at home alone, watching a horror movie. It is late at night. The

sky is pitch black except for an intermittent flash of lightening. Raindrops are pounding

against the window and tree branches are violently blowing in the wind. All of a sudden,

a loud crash of thunder makes you literally jump out of your chair. For a brief moment,

you experience a feeling of fear and your body prepares itself for anticipated action. The

emotional experience accompanying the physical response serves as a warning that action

may be required. Is there an intruder smashing your window? Should you run? Do you

need to protect yourself? Your physical response and corresponding emotional state

would likely be different if you were watching a comedy film, opposed to a horror movie,

at the time the thunder crashed. The preexisting apprehension experienced while viewing

a horror movie (in contrast to the relaxed, jovial state experienced while viewing a

comedy) exaggerates the physical reaction elicited in response to a sudden, potentially

threatening, stimulus. Thus, preexisting emotional states can influence subsequent

physiological responses. A wealth of research exists examining emotional and

physiological responses in humans. However, despite evidence suggesting ethnic

differences in emotional experiences and physiological responses, research on the

possibility of ethnic differences in the startle response, specifically, is lacking.

Research shows that emotional experiences are influenced by culture (Matsumoto,

1993). Cultures differ in terms of what is considered appropriate emotional expression

(Matsumoto, 1990) as well as actual display of emotion (Ekman, 1971; Friesen, 1972, as









cited by Matsumoto, 1993). Cultures also differ when judging faces and labeling which

emotion they perceive (Matsumoto, 1993). In addition, studies show cultural differences

in the subjective experience of emotion, including self-reported emotional experience

(e.g., intensity, duration, and control of emotion); verbal and nonverbal expressions; and

physiological sensations and reactions (Scherer et al., 1988; Matsumoto et al., 1988).

Investigating cultural differences by comparing samples from different countries is

a common practice in cross-cultural research on emotion. Although important

information is gained by examining international differences, exploring intranational

differences is also a fruitful endeavor, especially in ethnically diverse nations such as the

United States.

Emotion

Humans desire to attain pleasant things and to avoid unpleasant things. This

hedonistic orientation is not merely a means of self-gratification, but is adaptive in that it

functions to promote survival. In humans, the behaviors of moving toward positive

things and moving away from negative things are accompanied by emotion (Bradley &

Lang, 2000). In addition to reported feelings (e.g., happiness, sadness, fear, anger, and

love), emotions possess a biological component, regarded by many theorists as a product

of evolution (e.g., Davis & Lang, 2003; Frijda, 1986; Izard, 1977). Emotions function to

promote survival and reproduction by signaling situations that require immediate

attention, motivating adaptive behaviors, and serving as tools for communication (Leary,

Koch, & Hechenbleikner, 2001). Researchers propose a two-factor motivational

organization of emotion, suggesting that emotions are organized as responses to stimuli

that are either generally positive (appetitive) or negative aversivee) in nature (Dickinson

& Dearing, 1979; Konorski, 1967; Lang, Bradley, & Cuthbert, 1998). According to the









motivational organization proposed by Lang et al. (1998), situations that promote

survival (e.g., copulation) prime the activation of the appetitive system, whereas

situations involving threat (e.g., attack) prime the activation of the defensive system.

To scientifically study emotions and the underlying motivational systems, they

must be measurable. Emotions can be organized into three measurable systems: language

(e.g., cries of distress, self-reported descriptions of feelings), physiological reactions

(e.g., heart rate, skin conductance change, reflexes), and behaviors (e.g., approach,

avoidance) (Lang, 1993). The elicitation of measurable behavioral responses (e.g.,

fleeing the room) is difficult, if not impossible, under the current ethical guidelines. Self-

report data are often susceptible to social desirability, and people may not always be

capable of accurately identifying and reporting their own emotional responses (especially

physiological reactions such as subtle changes in facial muscle tension). Thus, poor

levels of covariation between these systems often occur (Bradley & Lang, 2000).

Although self-report data are useful, it may be helpful for researchers interested in the

physiological correlates of emotion to employ physiological measures to acquire

supplementary data that self-report measures alone are unable to provide.

Startle

When presented with a sudden threatening stimulus (e.g., a loud crash of thunder),

the defensive system quickly responds with a startle response, or startle reflex, to protect

the body from potential injury. The startle response consists of a behavioral repertoire,

including: hunching of the shoulders, pulling the head down and forward, clenching of

the fists, and quickly closing the eyes (i.e., blinking) (Hunt & Clarke, 1937). The

eyeblink is the most stable component of the startle response (Bradley & Lang, 2000;

Lang, Bradley, & Cuthbert, 1990) and can be measured by electrodes placed below the









eye, over the orbicularis oculi (the muscle responsible for the eyeblink). Researchers

conducting psychophysiological research often utilize the eyeblink as one measure of the

startle reflex, and thus, as an indicator that the defensive system is engaged. The startle

response serves as a defensive reflex that is heightened in situations providing evidence

of threat or other potential harm (e.g., attack) and is inhibited (or decreased) in contexts

promoting survival (e.g., sustenance) (Bradley, Cuthbert, & Lang, 1999). Thus, the

startle reflex provides one useful physiological measure in the study of emotion.

Researchers use a number of measures to quantify the startle response. Startle

probability provides information regarding the likelihood of a startle reflex. Startle

magnitude provides a useful measure of startle size by averaging across all trials, even

trials where no startle reflex occurred. However, a significant difference in startle

magnitude between two groups may be caused by 1) the actual size of the startle response

being larger in one group compared to the other, 2) the probability of a startle response

being greater in one group compared to the other, or 3) both 1 and 2. In contrast to

magnitude, which includes all trials, startle amplitude includes only trials where a valid

startle response occurred. Amplitude provides information regarding the actual size of

the startle response, controlling for possible differences in the probability of a response.

Affect and Startle

The viewing of emotionally laden stimuli (such as photographs from the

International Affective Picture System) is accompanied by a motivational state

commensurate with the affective content of the picture. For example, a stimulus that

indicates potential threat produces a defensive motivational state, whereas a stimulus

signifying pleasantness produces a positive, or appetitive, motivational state. The

emotional reactions associated with each motivational state affect the degree to which the









startle reflex is exhibited in response to a startle probe (e.g., a burst of noise, a bright

light). That is, the affective valence (i.e., degree of pleasantness or unpleasantness) of the

stimulus affects the elicited startle reflex in very predictable ways. Consistent with the

previously mentioned motivational priming hypothesis proposed by Lang et al. (1998),

the standard finding in psychophysiological research on the startle response is a linear

trend corresponding to a relative decrease (or attenuation) of the startle response when

attending to a pleasant stimulus, and a relative increase (or potentiation) of the startle

response when attending to an unpleasant stimulus, as compared to a neutral stimulus

(Bradley et al., 1999; Lang et al., 1990; Vrana, Spence, & Lang, 1988). This "affective

modulation" of the startle response reflects not only the motivational system that is

activated (the defensive system) by the startle probe itself but also the motivational

system that is activated by the affective valence of the stimulus being attended to at the

time the startle probe is presented.

A startle probe is, by definition, an unpleasant stimulus intended to evoke a sudden

response from the defensive system. According to the affective-match hypothesis (Lang

et al., 1990), if the affective valence of the stimulus that is being attended to (i.e., the

foreground stimulus) matches that of the startle probe (i.e., unpleasant), the startle

response elicited by that probe will be relatively augmented. Relative inhibition of the

startle reflex occurs during an affective "mismatch"; that is, if the foreground stimulus is

pleasant during the presentation of an unpleasant startle probe. For example, if a person

is already reacting to an unpleasant stimulus, such as a horror movie, the reflex elicited

by the presentation of a sudden burst of noise will be greater than if the person were

reacting to a pleasant stimulus, such as a comedy film, at the moment of startle probe









presentation. Affective modulation of the startle reflex is not, however, limited to the

acoustic startle probe modality.

Startle Probe Modality

Various probes are used in psychophysiological research to elicit the startle

response from human participants, including acoustic (e.g., bursts of white noise) (Lipp et

al., 2003; Vrana, 1994), visual (e.g., flashes of bright light) (Bradley et al., 2000), and

tactile (e.g., air puffs) (Hawk & Cook, 1997). Individual differences in startle reflex

magnitude are found to be stable across startle probe modalities, in that people who

respond with relatively large startle reflexes to an acoustic startle probe also respond with

relatively large startle reflexes to a visual startle probe (Bradley et al., 2000). Previous

research finds that startle responses elicited by an acoustic probe are consistently larger

than responses elicited by a visual probe. This difference has been attributed to

differences in probe intensity as opposed to differences in modality (Bradley et al., 2000).

Regardless of the rated aversiveness of the probe, affective modulation of the startle

response is consistently shown regardless of the modality of the startle probe, with larger

reflexes elicited when viewing unpleasant compared to pleasant pictures (Bradley et al.,

2000; Lang, Bradley, & Cuthbert, 1990).

Ethnic Differences in Physiology

As previously mentioned, studies have shown ethnic differences in the perceived

appropriateness (Matsumoto, 1990), display (Ekman, 1971; Friesen, 1972, as cited by

Matsumoto, 1993), and subjective experience (Scherer et al., 1988; Matsumoto et al.,

1988) of emotion. In addition, there is an extant literature revealing ethnic differences in

physiological responding, specifically between African Americans and European

Americans. Studies show that African Americans have lower skin conductance levels









than European Americans (Bernstein, 1965; Johnson & Corah, 1963; Johnson & Landon,

1965; Juniper & Dykman, 1967; Malmo, 1965) and also higher rates of hypertension

(Adams, 1932; Anderson, 1989; Haffner et al., 1990; Pappas, Gergen, & Carroll, 1990;

Winkleby, Fortmann, & Rockhill, 1993). Recently, Brown, Bradley, and Lang (2002)

found ethnic differences in the startle response to an acoustic probe.

The results of Brown et al. (2002) showed an ethnic difference in startle

magnitude (size of the startle response averaged across all trials, including those trials

where no startle occurs) as well as the probability of a startle response. However, their

data showed no ethnic difference in the size of the startle response averaged across only

those trials where a startle occurs (amplitude) or in affective modulation (the standard

valence effect occurs for each ethnic group). Thus, when a startle response did occur,

there was no difference in the size of the response between African Americans and

European Americans; however, African Americans startled less often than European

Americans in response to an acoustic startle probe.

Rationale for Current Study

The startle reflex is a useful tool for studying emotion. As mentioned above,

studies show that startle responses are consistent across probe modalities (i.e., people

who exhibit a relatively large startle response to an acoustic probe also exhibit a

relatively large response to a visual startle probe) (Bradley et al., 2000). Also, affective

modulation occurs across startle probe modalities (Bradley et al., 2000; Lang et al.,

1990). Although previous research finds systematic differences in a number of

physiological measures between different ethnic groups, a recent search of PsycInfo and

PubMed resulted in no entries pertaining to the investigation of ethnic differences in the

startle response. Based on the lack of entries in the literature, researchers appear to study









the startle reflex without addressing possible differences between ethnic groups. This

oversight may be problematic, especially for researchers collecting data from an

ethnically diverse sample. Systematic differences between ethnic groups in startle may

confound results if not properly taken into consideration.

Recent findings of Brown et al. (2002) showing ethnic differences in startle reflex

probability and magnitude between African Americans and European Americans in

response to an acoustic startle probe beg the question of why these differences occur.

One possible explanation is a difference in hearing between ethnic groups. Research

suggests that African Americans are less likely than European Americans to recognize

the symptoms and risks associated with excessive noise exposure (Crandell, Mills, &

Gauthier, 2004), and thus may be more likely to engage in behaviors that might lead to

hearing impairment. A classic sign of noise induced hearing loss is a permanent decrease

in hearing sensitivity in the frequency range of 3000-6000Hz (Henderson, Hamernik,

Dosanjh et al., as cited by Crandell et al., 2004). Because this is the frequency range of

the typical acoustic startle probe, hearing differences may account for differences in

startle reflex probability and magnitude, in that African Americans may be less sensitive

to an acoustic startle probe compared to European Americans. In addition to why the

ethnic difference occurs, the replicability of the effect, the generalizability of the effect to

other startle probe modalities, and the generalizability of the startle reflex as an indicator

of emotion across ethnic groups (and across startle probe modalities) require further

examination.

Research Question

The current study attempts to answer the following questions: 1) Are the ethnic

differences previously found by Brown et al. (2002) in the probability and magnitude of









the startle response specific to the acoustic startle probe modality or the results of more

general ethnic differences in defensive responding? 2) Does affective modulation of

startle reflex magnitude occur for African American as well as European American

participants in response to both acoustic and visual startle probes?

Hypotheses

Ethnic Differences in Startle

If the ethnic differences in startle probability and magnitude in response to an

acoustic startle probe found by Brown et al. (2002) are specific to the auditory modality

(e.g., due to hearing differences), ethnic differences in the startle reflex are expected in

response to an acoustic startle probe but not in response to a visual startle probe.

However, if the previously found ethnic differences are indicative of more general ethnic

differences in basic defensive responding, ethnic differences are expected in startle

reflexes elicited by both an acoustic and a visual startle probe.

Affective Modulation

Based on previous research examining affective modulation in response to startle

probes presented through different modalities (e.g., acoustic and visual), replication of

the standard affective modulation effect on startle magnitude is expected for both an

acoustic and a visual startle probe for both European Americans and African Americans.















CHAPTER 2
METHOD

Participants

Participants were 16 African American (9 female and 7 male) and 16 European

American (7 female and 9 male) Introductory Psychology students at the University of

Florida. One European American female was paid for her participation in the study while

all other students received partial course credit for their participation. The mean age of

participants was 18.91 years and all of the students were between 18 and 21 years of age.

Materials and Design

Stimuli

The International Affective Picture System (or IAPS) is a standardized collection

of over 700 pictures selected as affect-inducing stimuli (Lang, Bradley, & Cuthbert,

2001). Research shows that the IAPS serves this purpose well, providing photographic

images that produce the desired range of emotional reactions, with varying degrees of

intensity (Lang et al., 1993). The IAPS contains photographs depicting people, animals,

nature, and objects, previously rated for valence (i.e., degree of pleasantness or

unpleasantness) and arousal (i.e., intensity of activation).

Thirty-six pictures were selected from the IAPS (Lang et al., 2001) for the current

study. Pictures were chosen, based on their standardized ratings, to represent three

affective valence categories (i.e., pleasant, neutral, unpleasant). The pleasant category

was comprised of erotic pictures, including pictures of heterosexual couples and other

(i.e., opposite) sex nudes. Neutral pictures included both indoor and outdoor scenes or









objects. The unpleasant category consisted of pictures depicting physical threat,

including attacking animals and attacking humans. Each of the three valence categories

included 12 different pictures. 1

Two different orders of picture presentation were constructed to control for

possible effects resulting from viewing pictures in a particular sequence. Each order was

arranged in blocks of six, such that there were two exemplars from each of the three

stimulus valence categories in each block of six, resulting in one picture from each

content category in each block. That is, each block of six pictures contained two erotic

pictures (one couple and one other sex nude), two neutral pictures (one inside and one

outside neutral scene or object), and two unpleasant threat pictures (one animal attack and

one human attack). Each order included identical pictures; however, arrangement

occurred so that pictures would not immediately precede or follow the same pictures

across blocks. Within each order, the other sex nudes were either of females (viewed by

male participants) or of males (viewed by female participants), providing a total of four

different picture combinations (i.e., order 1 for males, order 1 for females, order 2 for

males, order 2 for females). Each participant was presented with only one picture order.

Digitized versions of the IAPS pictures were projected by an LCD projector onto a large

(70" x 56") screen, which was positioned approximately 6 feet in front the participant.

Picture onset was nearly instantaneous, and each picture was presented for 6 seconds.

Between each picture presentation (i.e., trial), an inter-trial interval (ITI) period (ranging



1 IAPS numbers used in this study were: Pleasant: 4002, 4669, 4290, 4652, 4687, 4220, 4310, 4611, 4180,
4658, 4250, 4672 (pictures 4002, 4290, 4220, 4310, 4180, 4250 were erotic pictures of females shown to
male participants; pictures 4531, 4520, 4534, 4536, 4533, 4535 were erotic male pictures shown to female
participants); Neutral: 7710, 5950, 7283, 5900, 7490, 5500, 7207, 5731, 7170, 5740, 5920, 7237;
Unpleasant: 6212, 1050, 1220, 6350, 6313, 1270, 6243, 1280, 1301, 6230, 1930, 6570.









in length from 8s to 16s) occurred when the screen was blank. All pictures were

displayed in 32-bit color.

Startle Probes

The acoustic startle probe consisted of a 50-ms, 95dB burst of white noise, produce

by a Coulbourn S81-02 white-noise generator. The stimulus was then gated through a

Coulbourn S82-24 amplifier and presented to the participant over TDH-49 headphones.

The headphones covered both ears of the participant, providing equal noise intensity to

both ears. The visual startle stimulus consisted of a flash of light generated by the

simultaneous firing of three professional photography flashguns. The three flashguns

were positioned approximately 6 ft in front of the participant, and were not directed

toward the participant. The startle probe was presented between 2.5 and 3.5s after each

picture onset, as well as during 14 of the inter-trial intervals. During picture viewing, 18

acoustic startle probes were presented (6 per valence) and 18 visual startle probes were

presented (6 per valence). Within each block of six pictures, three acoustic and three

visual startle probes occurred. Either an acoustic or a visual startle probe was presented

during each picture, with the constraint that if an acoustic probe was presented during a

particular picture in order 1, a visual probe was presented during that same picture in

order 2 (and vice versa). Participants received a total of seven acoustic and seven visual

startle probes during inter-trial intervals.

Hearing Test

To examine hearing differences as a possible explanation for the ethnic differences

found by Brown et al. (2002), a hearing test was conducted on each participant using a

GSI-17 Audiometer (Grason-Stadler, Inc., Madison, WI). Participants' hearing









thresholds were measured in decibels (dB) for 10 different frequencies ranging from 250

Hz-8000 Hz.

Questionnaires

A pre-experimental questionnaire, comprised of the Personal Need for Structure

Scale (Thompson, Naccarato, & Parker, 1989, as cited in Neuberg & Newsom, 1993) and

the Interaction and Audience Anxiousness Scale (Leary, 1983) was completed by all

participants (see Appendixes A and B, respectively). However, these measures were not

relevant to the current investigation and are not mentioned further. A post-experimental

questionnaire (see Appendix C), including basic demographic questions and items

assessing the participant's subjective experience, was administered at the conclusion of

the experimental session. Of specific interest to the current study were items assessing

the pleasantness of the startle probes. Items asked participants to "rate the pleasantness

of noises heard over headphones while watching pictures during the course of the

experiment" and to "rate the pleasantness of flashes of light seen while watching pictures

during the course of the experiment". Each of these items was scored on a 7-point scale,

1 = unpleasant, 7 = pleasant. All questionnaires are included in the Appendix.

Startle Eyeblink Measurement and Reduction

The eyeblink component of the startle response was measured by placing two 4mm

In Vivo Metric (Healdsburg, CA) miniature electrodes over the inferior orbicularis oculi,

using the placement recommended by Fridlund and Cacioppo (1986). Physiological data

were acquired using an IBM-compatible computer running VPM version 11.2 data

acquisition and reduction software (Cook, 2000). The raw electromyography (EMG)

signal was amplified (x30,000), and frequencies below 90 Hz and above 250 Hz were

filtered with a Coulbourn S75-01 bioamplifier. The raw signal was rectified and









integrated with a Coulboum S76-01 contour-following integrator, with a time constant of

200ms. Activity in the orbicularis oculi muscle was sampled at 20 Hz during baseline

and picture viewing, with an increase in sampling rate to 1,000 Hz for 50 ms before the

onset of the startle probe and for 250 ms after probe onset. The eyeblink data were

reduced off-line by using a program that scored each trial for magnitude in analog-to-

digital (A/D) units, using an algorithm devised by Globisch, Hamm, Schneider, and Vaitl

(1993). Corrugator (frowning muscle) EMG activity was also measured in the

experimental sessions but is not relevant to the current hypotheses and therefore is not

reported.

Procedure

Participants were run individually. Participants sat in a recliner in a 9' x 13' dimly

lit room. After providing informed consent and completing the pre-experimental

questionnaire, a brief hearing test was administered. Participants were notified that a set

of earphones would be placed over their ears and a variety of tones would be heard. They

were instructed, in accordance with the instruction manual accompanying the GSI-17

Audiometer, to indicate when a tone was heard by raising the hand corresponding to the

ear in which the tone was heard, and then lowering the hand when the tone was no longer

heard. Participants were familiarized with the tone by receiving a sample tone at 1000

Hz and 40 dB. Hearing threshold was determined by presenting the tone for 1-2 seconds

and increasing the volume level by 5 dB after each failure of the participant to respond.

The threshold is the minimum volume setting at which the participant indicates that the

tone is audible. The setting level (in dB) was then recorded as the hearing threshold. The

testing procedure was repeated for each tone frequency setting, 250 Hz, 500 Hz, 1000 Hz,









1500 Hz, 2000 Hz, 3000 Hz, 4000 Hz, 6000 Hz, and 8000 Hz, for the left ear and then for

the right ear.

Participants were then prepared for physiological recording. The skin under the

eye was cleansed with water and a tissue to remove any makeup, oil, etc. that might

impede the electrical signal. Electrolyte gel was placed inside the electrode cups as well

as gently rubbed on the skin of the participant. Electrodes were then placed on the

participant. Participants were instructed to attend to each picture throughout its duration

and to remain as still as possible. A set of headphones was placed over the participants'

ears and was worn throughout the picture-viewing period to provide a channel for

administering the acoustic startle probe. The lighting was dimmed, the door closed, and

the participant was alone while viewing the pictures. The picture viewing session lasted

approximately 17 minutes, after which the electrodes were removed from the participant

and a post-experimental questionnaire was administered. Participants were subsequently

debriefed, thanked for their participation, and dismissed.

Analyses

Analyses were conducted to assess effects of startle probe modality, picture

valence, and ethnicity on magnitude, probability, and amplitude of the startle response.

A 2 (startle probe modality: acoustic, visual) X 3 (picture valence: pleasant, neutral,

unpleasant) X 2 (ethnicity: African American, European American) mixed-model

ANOVA was conducted in which startle probe modality and picture valence were within

subject factors and ethnicity was a between subjects factor. Because only those startle

responses occurring while pictures were presented were of interest, startles occurring

during inter-trial intervals were not analyzed. In cases where a significant effect of

affective valence occurred, pairwise comparisons were subsequently conducted to









determine the pattern of differences between the three levels (pleasant, neutral,

unpleasant). All pairwise analyses were Bonferroni corrected for multiple comparisons.

Based on the recommendations of Vasey and Thayer (1987) regarding within subject

psychophysiological data, the multivariate Wilks' Lambda test statistic is reported for all

analyses including within subject variables. All means for magnitude and amplitude are

reported in A/D units. All means for probability are expressed as a ratio of the number of

trials during which a startle response occurred divided by the total number of trials. Data

from three participants were excluded from analyses including startle probe modality as a

factor due to startle responses that could not be used. Fourteen participants were

excluded from analyses involving startle amplitude due to either startle responses that

could not be used or lack of a startle response. Startle responses were determined to be

unusable if the onset of the eyeblink occurred longer than 150ms after the presentation of

the startle probe.

Effects of participant ethnicity on hearing threshold were assessed by conducting a

mixed-model analysis of variance (ANOVA), with participant ethnicity as a between

subjects factor and tone frequency as a within subject factor. Because only the higher

frequencies (3000, 4000, 6000, and 8000 Hz) are pertinent to the acoustic startle response

(W. K. Berg, personal communication, January, 2004), only analyses involving these

frequencies are reported.















CHAPTER 3
RESULTS

Magnitude

Probe Modality

Consistent with the results of previous studies (e.g., Bradley et al., 2000), startle

magnitude was affected by the modality of the startle probe, F (1, 27) = 14.10, p = .001,

eta-squared= .343, in that a response elicited by an acoustic probe (M= 180.52, SD=

199.14) was greater than one elicited by a visual probe (M= 56.39, SD = 73.88).

Valence

The magnitude of the startle reflex was modulated by the affective valence of the

picture stimulus, F (2, 26) = 7.60, p < .01, eta-squared= .369. The size of the startle

response was different depending on whether the participant was viewing a pleasant

picture, neutral picture, or unpleasant picture at the time the startle probe was presented.

Picture valence and startle probe modality interacted to produce an effect on startle

magnitude, F (2, 26) = 3.66, p < .05, eta-squared= .220. The nature of this interaction

was examined more closely by analyzing the effect of picture valence on startle

magnitude separately for acoustic and visual startle probes. Replicating previous

findings, results revealed a significant effect of picture valence on blink magnitude for

the acoustic startle probe, F (2, 30) = 6.83, p < .005, eta-squared= .313. Figure 3-1 (top

panel) illustrates the pattern of startle reflex magnitude obtained in response to an

acoustic startle probe while viewing affective pictures.













Pleasant Neutral Unpleasant


Acoustic Startle Probe


FL


Pleasant


adIIIIII


I t --


Neutral Unpleasant


Visual Startle Probe
Figure 3-1. Top panel: Startle blink magnitude when elicited by an acoustic startle
probe, while viewing pleasant, neutral, or unpleasant pictures. Bottom panel:
Startle blink magnitude when elicited by a visual startle probe, while viewing
pleasant, neutral, or unpleasant pictures.
Planned pairwise analyses revealed that larger blinks were elicited by an acoustic
probe when viewing unpleasant (M= 192.36, SD = 199.98) compared to pleasant (M=


Afl


w


1


Af% I









136.09, SD = 173.68) pictures,p < .01, and smaller blinks were elicited when viewing

pleasant (M= 136.09, SD = 173.68) compared to neutral (M= 190.30, SD = 204.68)

pictures, p < .01. No difference in blink magnitude was found when viewing neutral (M

= 190.30, SD = 204.68) compared to unpleasant (M= 192.36, SD = 199.98) pictures, p =

ns, when elicited by an acoustic probe.

Results also revealed a significant effect of picture valence on blink magnitude for

the visual startle probe, F (2, 27) = 4.11, p < .05, eta-squared = .233. Figure 3-1 (bottom

panel) illustrates the pattern of startle reflex magnitude obtained in response to a visual

startle probe. Planned pairwise comparisons revealed that larger blinks were elicited

when viewing unpleasant (M= 63.84, SD = 75.49) compared to pleasant (M= 49.28, SD

= 67.33) pictures, p < .05. No differences in blink magnitude were found when viewing

pleasant (M= 49.28, SD = 67.33) compared to neutral (M= 57.70, SD = 87.43) pictures,

p = ns, or when viewing neutral (M= 57.70, SD = 87.43) compared to unpleasant (M=

63.84, SD = 75.49) pictures, p = ns.

Ethnicity

In contrast to results found by Brown et al. (2002), the magnitude of the startle

response did not differ between African American participants (M= 120.45, SD =

168.10) and European American participants (M= 116.45, SD = 174.00), F (1, 27) < l,p

= ns, eta-squared = .000. Ethnicity did not interact with picture valence, F (2, 26) = 1.19,

p = ns, eta-squared = .084, or startle probe modality, F (1, 27) <1, p = ns, eta-squared=

.026, to affect startle magnitude. The three way interaction between picture valence,

startle probe modality, and ethnicity was also not significant for startle magnitude, F (2,

26) = 1.24, p = ns, eta-squared = .087. Thus, the ethnicity of the participant did not affect

the pattern of affective modulation obtained in response to either an acoustic or a visual









startle probe. Figure 3-2 illustrates the patterns of startle reflex magnitude obtained from

European American and African American participants in response to acoustic (top

panel) and visual (bottom panel) startle probes.


Eur Am


O Pleasant
0 Neutral
I Unpleasant


Afr Am


Acoustic Startle Probe


O Pleasant
0 Neutral
El Unpleasant


Eur Am Afr Am


Visual Startle Probe

Figure 3-2. Startle blink magnitude obtained from European American and African
American participants in response to acoustic (top panel) and visual (bottom
panel) startle probes.









Probability

Probe Modality

Replicating previous studies, the probability of a startle response was significantly

affected by startle probe modality, F (1, 27) = 19.42, p < .001, eta-squared= .418. The

likelihood of an occurrence of a startle response elicited by an acoustic probe (M= .77,

SD = .30) was greater than the likelihood of an occurrence of a startle response elicited

by a visual probe (M= .46, SD = .35).

Valence

The picture valence affected the probability of an occurrence of a startle response,

F (2, 26) = 3.26, p = .05, eta-squared= .201. Figure 3-3 depicts the pattern of startle

response probability obtained while viewing affective pictures. Pairwise comparisons

revealed that the likelihood of a startle response was greater when viewing unpleasant

(M= .66, SD = .26), compared to pleasant (M= .58, SD = .30) pictures, p < .05.

No differences occurred, in terms of probability, between startles elicited while viewing

pleasant pictures (M= .59, SD =.29) compared to neutral pictures (M= .60, SD = .27), p

= ns, or neutral pictures (M= .60, SD = .27) compared to unpleasant pictures (M= .66,

SD = .26), p = ns Startle probe modality and picture valence did not interact to produce

an effect on startle response probability, F (2, 26) = 2.71, p = ns, eta-squared = .172.











0.7


0.65-


00


S 0.55


0.5
Pleasant Neutral Unpleasant






Figure 3-3. The probability of a startle response, averaged across acoustic and visual
startle probe modalities, while viewing pleasant, neutral, or unpleasant
pictures.

Ethnicity

Results did not show a significant difference between African American

participants (M= .611, SD = .37) and European American participants (M= .614, SD =

.38) in the probability of a startle response, F (1, 27) < 1, p = ns, eta-squared= .000.

Participant ethnicity did not interact with picture valence, F (2, 26) < 1, p = ns, eta-

squared = .053, or probe modality, F (1, 27) < 1, p = ns, eta-squared = .028, to affect the

probability of a startle response. The three-way interaction between picture valence,

probe modality, and participant ethnicity was also not significant for probability, F (2,

26) < 1, p = ns, eta-squared = .067.









Amplitude

Recall that startle amplitude is calculated by averaging startle size over trials where

a startle response occurred. Thus, amplitude is an indication of startle size, controlling

for probability.

Probe Modality

The modality of the startle probe affected the amplitude of the startle response, F

(1, 16) = 9.55, p < .01, eta-squared= .374. Eye-blinks elicited by acoustic startle probes

were larger (M= 254.27, SD = 212.73) than those elicited by visual startle probes (M=

108.97, SD = 69.15).

Valence

The affective valence of the picture stimulus significantly affected the amplitude

of the startle response, F (2, 15) = 6.94, p < .01, eta-squared= .481. Figure 3-4 illustrates

the pattern of startle reflex amplitude, across startle probes, obtained while viewing

affective pictures. Pairwise analyses revealed larger blinks were elicited while viewing

unpleasant (M= 194.15, SD = 127.42) compared with pleasant (M= 150.04, SD =

114.59) pictures, p <.01. Smaller blinks were elicited while viewing pleasant (M=

150.04, SD = 114.59) compared with neutral (M= 200.67, SD = 134.89) pictures, p < .01.

Startle responses while viewing neutral pictures (M= 200.67, SD = 134.89) did not differ

in amplitude compared with responses while viewing unpleasant (M= 194.15, SD =

127.42) pictures, p = ns Picture valence and startle probe modality did not interact to

affect startle amplitude, F (2, 15) = 2.71, p = ns, eta-squared= .266.











220

200

180

S160

140

120

100
Pleasant Neutral Unpleasant



Figure 3-4. Startle blink amplitude, averaged across acoustic and visual startle probe
modalities, while viewing pleasant, neutral, or unpleasant pictures.

Ethnicity

African American participants (M= 196.61, SD = 122.76) and European American

participants (M= 166.63, SD = 122.76) did not differ in startle amplitude, F (1, 16) < 1, p

= n.s, eta-squared= .017. Participant ethnicity did not interact with picture valence, F (2,

15) = 2.72, p = ns, eta-squared= .266, or probe modality, F (1, 16) < 1, p = ns, eta-

squared = .005, to affect startle amplitude. The three-way interaction between picture

valence, probe modality, and participant ethnicity was also not significant for amplitude,

F (2, 32) < 1, p = ns, eta-squared = .042.

Tests of Alternative Explanations

Hearing

Because the acoustic startle probe was presented through headphones to both the

left and right ears simultaneously, the hearing data were averaged across both ears.

Results showed that ethnicity had no effect on hearing threshold, F (1, 30) < 1, p = ns,









eta-squared= .016. The average decibel level at which a tone in the frequency range of

3000-8000 Hz was audible (i.e., hearing threshold) was not significantly different

between African American (M= 7.89, SD = 4.17) and European American (M= 7.58, SD

= 4.17) participants. Mean hearing thresholds for each ethnic group at each frequency

level are reported in Figure 3-5.


18-
a 16-
S14
S12
10-
8- O Eur Am
6- 0 Afr Am
4
2-LI
0 -
250 500 750 1000 1500 2000 3000 4000 6000 8000
Frequency



Figure 3-5. Mean hearing thresholds for each ethnic group at each frequency level.

Subjective Ratings of Startle Probes

A 2 (startle probe modality: acoustic, visual) X 2 (ethnicity: African American,

European American) mixed-model ANOVA was conducted on the subjective ratings of

the pleasantness of the startle probes, with startle probe modality as a within subjects

factor and participant ethnicity as a between subjects factor. Results revealed that

acoustic startle probes (M= 2.16, SD = .88) were consistently rated as more unpleasant

than visual startle probes (M= 3.00, SD = 1.05), F(1, 30) = 16.01, p< .0001, eta-squared

= .348. In addition, African Americans (M= 2.31, SD = .72) rated the startle probes in






26


general as more unpleasant, compared with European Americans (M= 2.84, SD = .72), F

(1, 30)= 4.29, p < .05, eta-squared= .125. Probe modality and participant ethnicity did

not interact to affect subjective ratings of the startle probes, F (1, 30) = 1.08,p = ns, eta-

squared= .035.














CHAPTER 4
DISCUSSION

It was hypothesized that if the ethnic differences in probability and magnitude

previously found by Brown et al. (2002) were due to general ethnic differences in

defensive responding, their results would be replicated in response to an acoustic as well

as a visual startle probe. If, however, the ethnic differences previously found by Brown

et al. were somehow specific to an acoustic startle probe (perhaps due to hearing

differences), replication of the previously found results with an acoustic startle probe but

not with a visual probe was expected. In contrast to expectations, the current study did

not show any ethnic differences in the startle response in terms of magnitude, probability,

or amplitude. Not only did no ethnic differences occur in the startle reflex in response to

a visual probe, but replication of Brown et al., (2002) of ethnic differences in probability

and magnitude was also not attained in response to an acoustic probe.

One possible explanation for the ethnic differences in startle found by Brown et

al. (2002) is a difference in hearing between the two ethnic groups. For an acoustic

startle probe to be effective, it must be heard. Thus, the quality of auditory processing

might affect the probability and size of the startle response. Individuals with optimal

auditory processing capability would likely exhibit a greater probability of startle as well

as enhanced startle size compared to individuals with suboptimal auditory processing

capability. However, results showed no difference in ability to hear between African

American and European American participants, suggesting that differences in hearing did

not contribute to the differences in acoustically elicited startle previously found by Brown









et al. (2002). The failure to replicate previously found ethnic differences in response to

an acoustic startle probe initiates the exploration of possible explanations that may

account for the incongruity of results.

If one ethnic group rated the startle probes as more unpleasant compared to the

ratings of the other ethnic group (indicating a more aversive experience), differences in

the size and/or probability of a startle response may be attributable to differences in

subjective experience. African American participants did, in fact, indicate that the startle

probes were more unpleasant than the European American participants did; however,

results showed no ethnic differences in actual startle size or probability. Moreover, the

ethnic difference in subjective ratings does not offer an explanation for the findings of

Brown et al. (2002). The current study found that African American participants,

compared with European American participants, found the startle probes to be more

unpleasant. If subjective experience directly affected the startle response, it would be

expected that African American participants would actually exhibit greater startle

probability and enhanced startle size compared to European Americans. However, the

direction of means of the subjective ratings is counter to what would be expected if

subjective experience directly affected the startle response.

There are differences that exist between the Brown et al. (2002) study and the

current study that may be offered as possible explanations for the incongruity of the

results regarding ethnic differences in the probability and magnitude of startle. First, the

picture sets were different. Although both sets of pictures are from the IAPS collection

and both include pictures representing pleasant, neutral, and unpleasant valences, picture

content was not identical in the two studies. For example, almost two thirds of the









pictures in the Brown et al. study were of people, and included depictions of mutilated

bodies in addition to threat in the unpleasant valence category. Only half of the pictures

in the current study depicts people (the other half is comprised of animals, objects, and

scenes), and the unpleasant valence category does not include any depictions of mutilated

bodies, but only threat. The current study attempted to replicate previously found ethnic

differences in startle reflex magnitude and probability in response to an acoustic probe

and investigate whether ethnic differences extend to another startle probe modality.

Therefore, the picture set used was similar to the picture set utilized by Bradley et al.

(2000) in their study revealing the stability of individual differences in startle response

size across startle probe modalities. Future research is needed to investigate the possible

effects of specific picture content on ethnic differences in startle. Specifically, an

investigation of ethnic differences in the startle response across probe modalities utilizing

the stimulus picture set from the Brown et al. study may be helpful in shedding light on

whether ethnic differences in startle are dependent on specific picture stimuli.

Second, the ethnicity of the experimenters) is different. In the Brown et al.

(2002) study, some participants interacted with both an African American and a

European American female experimenter, while others interacted with either an African

American or a European American female experimenter. In the current study,

participants interacted only with a European American female experimenter. Because

participant ethnicity was examined as a source of possible differences, it seems possible

that the ethnicity of the experimenter might also affect the participants' reactions. The

effect of the experimenter's ethnicity, however, was examined in the Brown et al. study









and did not have any effect on participants' startle response. Therefore, the difference in

experimenter ethnicity seems an unlikely explanation for the inconsistent findings.

Third, the sample is different. In addition to the sample in the Brown et al. (2002)

study being over two and half times larger than that of the current study, it is possible that

only a subpopulation of African Americans exhibit decreased startle probability and

magnitude compared to European Americans. Research investigating the startle reflex in

animal samples in response to an acoustic startle probe has found differences in startle

size among inbred strains of mice (Willott et al., 2003) and rats (Conti & Printz, 2003).

In addition, differences in startle magnitude have been found in rats with predispositions

for different types of defensive behavior (e.g., passive "freezing" responses, aggressive

behavior) (Popova et al., 2000). Together, these results suggest that responsiveness to a

startle probe may be influenced by a genetic component. Thus, it is possible that a

subpopulation of African Americans display the pattern of startle response found by

Brown et al. (i.e., decrease in startle response probability and magnitude), but members

of that subpopulation were not included in adequate number in the current sample.

According to the motivational priming organization proposed by Lang et al.

(1998), situations that promote survival (e.g., copulation) prime the activation of the

appetitive system, whereas situations involving threat (e.g., attack) prime the activation

of the defensive system. The motivational priming organization predicts that startle

reflex size will be enhanced when the foreground stimulus (e.g., a picture) is unpleasant

and inhibited when the foreground stimulus is pleasant. In addition, the affective match

hypothesis proposed by Lang et al. (1990) proposes that the differentiation in startle

reflex size is based on whether the affective valence of the stimulus is matched or









mismatched with the affective valence of the startle probe. This position suggests that

affective modulation of the startle response is dependent on the affective match or

mismatch of the stimulus and the startle probe, not the modality of the probe itself. Thus,

affective modulation should occur regardless of whether the startle probe is acoustic or

visual. Based on the motivational priming organization and the affective match

hypothesis, it was expected that affective modulation would occur for a visual as well as

an acoustic startle probe. Due to the recently obtained ethnic differences in startle

probability and magnitude, it was deemed prudent to systematically test for ethnic

differences in affective modulation. However, because there was no explicit reason to

believe that ethnic differences would occur, it was predicted that affective modulation

would occur for both ethnic groups.

As expected, replication of the standard affective modulation effect for both ethnic

groups and for both startle probe modalities was attained, with larger startle reflex

magnitude elicited when viewing unpleasant, compared to pleasant, pictures. Because

startle magnitude is an indication of the emotional state of the individual at the time of

the startle probe presentation, results suggest that the startle response is a reliable

measure of emotion across ethnic groups.














CHAPTER 5
CONCLUSION

Until recently, researchers studying the startle response have not acknowledged the

possibility of ethnic differences, or at least have not reported systematically testing for

such differences. In light of the current findings, the possibility of ethnic differences in

the startle response is still unclear and future research is needed to further investigate this

line of study. Taken together, the current results suggest that the startle response is a

reliable measure of emotion for both European Americans and African Americans

whether elicited by an acoustic or a visual startle probe














APPENDIX A
PERSONAL NEED FOR STRUCTURE SCALE

Read each of the following statements and decide how much you agree with each
according to your attitudes, beliefs, and experiences. It is important for you to realize that
there are no "right" or "wrong" answers to these questions. People are different, and we
are interested in how you feel. Please respond according to the following 6-point scale.

1 = strongly disagree
2 = moderately disagree
3 = slightly disagree
4 = slightly agree
5 = moderately agree
6 = strongly agree

1. It upsets me to go into a situation without knowing what I can expect from it.
2. I'm not bothered by things that interrupt my daily routine.
3. I enjoy having a clear and structured mode of life.
4. I like to have a place for everything and everything in its place.
5. I enjoy being spontaneous.
6. I find that a well-ordered life with regular hours makes my life tedious.
7. I don't like situations that are uncertain.
8. I hate to change my plans at the last minute.
9. I have to be with people who are unpredictable.
10. I find that a consistent routine enables me to enjoy life more.
11. I enjoy the exhilaration of being in unpredictable situations.
12. I become uncomfortable when the rules in a situation are not clear.















APPENDIX B
INTERACTION AND AUDIENCE ANXIOUSNESS SCALE

For the next 15 items, read each of the following statements carefully and indicate how
characteristic it is of you according to the following scale:

1 = Not at all characteristic of me.
2 = Slightly characteristic of me.
3 = Moderately characteristic of me.
4 = Very characteristic of me.
5 = Extremely characteristic of me.

Please answer each question as accurately and honestly as you can.

1. I often feel nervous in casual get-togethers.
2. I usually feel uncomfortable when I'm in a group of people I don't know.
3. I am usually at ease when speaking to a member of the opposite sex.
4. I get nervous when I must talk to a teacher or a boss.
5. Parties often make me feel anxious and uncomfortable.
6. I am probably less shy in social interactions than most people.
7. I sometimes feel tense when talking to people of my own sex if I don't know
them very well.
8. I would be nervous if I was being interviewed for a job.
9. I wish I had more confidence in social situations.
10. I seldom feel anxious in social situations.
11. In general, I am a shy person.
12. I often feel nervous when talking to an attractive member of the opposite sex.
13. I often feel nervous when calling someone I don't know very well on the
telephone.
14. I get nervous when I speak to someone in a position of authority.
15. I usually feel relaxed around other people, even people who are quite
different from me.














APPENDIX C
POST-EXPERIMENTAL QUESTIONNAIRE


Age:

Date: Were you born in the U.S.? Yes

Year in school:

Do you consider yourself an American? Yes No

Gender (circle one): Female Male

Sexual orientation: Bisexual Gay/Lesbian Heterosexual

Ethnicity: Asian Biracial Black Hispanic White
Other:

Height: Weight:

Handedness: Left Right Ambidextrous

Are any of your biological relatives left-handed? Specify.


Did you ever switch handedness preferences? If so, explain:


If you are a woman, what are the approximate dates of your last menstrual period?


Do you wear glasses or contact lenses? Yes

Were you wearing them during the experiment?

Do you have hearing problems? Yes No


Do you have a chronic illness?


Do you have a current illness?


Yes No


Yes No


No

If so, please describe:


If so, please explain:


If so, please explain:










Do you take any special medication (for example, birth control pills, allergy medication,
anti-anxiety medicine, anti-psychotic medicine, stress relievers)? Yes No
If so, please explain:


Are you currently on any form of over-the-counter medication (for example, aspirin,
Tylenol, Advil, allergy medicine)? Yes No
If so, please explain:


Have you used any recreational drugs within the last 48 hours? Yes
If so, please specify:


Is there any pre-existing state you are in which could have affected your response to the
slides (for example, extreme excitement, sadness, happiness)?


Do you get anxious in small spaces? Yes

Rate pleasantness of sensors under eyes:


TTNPT.FASANT


PT.F ASANT


Rate pleasantness of noises heard over headphones while watching pictures during the
course of the experiment


UNPLEASANT


PLEASANT


Estimate the number of noises heard over the headphones during the course of the
experiment:





Rate confidence of this estimate


1
NOT VERY CONFIDENT


7
VERY CONFIDENT


Rate pleasantness of flashes of light seen while watching pictures during the course of the
experiment


1
UNPLEASANT


7
PLEASANT


Estimate the number of flashes seen during the course of the experiment:


Rate confidence of this estimate:


1 2


4 5


6 7









NOT VERY CONFIDENT VERY CONFIDENT


Was there any regularity in the pattern when noises were presented? Yes No
If so, please explain:



Was there any regularity in the pattern when flashes were presented? Yes No
If so, please explain:


Rate how much the noises over the headphones made you startle:
1 2 3 4 5 6 7
NOT VERY MUCH VERY MUCH

Rate how much the flashes of light made you startle:
1 2 3 4 5 6 7
NOT VERY MUCH VERY MUCH

What were you thinking about between picture presentations?




Could you see the pictures on the screen? Yes No

Please rate each of the following types of pictures in terms of how pleasant or unpleasant
you found them. Use this scale 1= Very Unpleasant, 4 = Neutral, 7 = Very Pleasant

Violence Erotica Household objects/scenes
Animals

Did you have trouble staying awake during the study? Yes No

Did you fall asleep at any time during the study? Yes No

What do you think was our hypothesis for this experiment?



Please add any additional comments you have about any aspect of the laboratory, the

experiment, or your experimenter:
















LIST OF REFERENCES


Adams, J. M. (1932). Some racial differences in blood pressure and morbidity in groups
of white and colored workmen. The American Journal of the Medical Science, 184,
342.

Anderson, N. B. (1989). Racial differences in stress-induced cardiovascular reactivity and
hypertension: Current status and substantive issues. Psychological Bulletin, 105,
89-105.

Bernstein, A. S. (1965). Race and examiner as significant influences on basal skin
impedance. Journal ofPersonality & Social Psychology, 1, 346-349.

Bradley, M. M, Cuthbert, B. N., & Lang, P. J. (1999). Affect and the startle reflex. In M.
E. Dawson, A. M. Schell, & A. H. Bohmelt (Eds.) Startle modification:
Implications for neuroscience, cognitive science, and clinical science. Cambridge
University Press.

Bradley, M. M., & Lang, P. J. (2000). Measuring emotion: Behavior, feeling, and
physiology. In R. Lane & L. Nadel (Eds),Cognitive Neuroscience ofEmotion,
Series in affective science. Oxford University Press, New York, NY. p. 242-276.

Bradley, M. M., Safi, F., Soler-Baillo, J., & Lang, P. J. (2000, October). Startle modality
and size: Is a big startler always a big startler? Poster presented at the 40th meeting
of the Society for Psychophysiological Research, San Diego, CA.

Brown, L. M., Bradley, M. M., & Lang, P. J. (2002, October). The role of ethnicity in
affective reactions to ingroup and outgroup pictures. Presented at a symposium
entitled What Has Psychophysiology Revealed About Ethnicity and Emotion?
chaired by Jeanne L. Tsai at the 42nd meeting of the Society for
Psychophysiological Research, Washington, DC.

Conti, L. H., & Printz, M. P. (2003). Rat strain-dependent effects of repeated stress on the
acoustic startle response. Behavioural Brain Research, 144, 11-18.

Cook, E. W., III. (2000). VPMreference manual. Birmingham, AL: Author.

Crandell, C., Mills, T. L., & Gauthier, R. (2004). Knowledge, behaviors, and attitudes
about hearing loss and hearing protection among racial/ethnically diverse young
adults. Journal of the National Medical Association, 96, 176-185









Davis, M. & Lang, P. J. (2003). Emotion. In M. Gallagher & R. J. Nelson (Eds.),
Handbook ofpsychology: Vol. 3. Biological psychology. New York: Wiley.

Dickinson, A. & Dearing M. F. (1979) Appetitive-aversive interactions and inhibitory
processes. In A. Dickinson & R. A. Boakes (Eds) Mechanisms ofLearning and
Motivation. Hillside, NJ, Erlbaum, pp 203-231.

Ekman, P. (1971). Universals and cultural differences in facial expressions of emotion. In
J. Cole (Ed.), Nebraska Symposium on Motivation. Lincoln: University of Nebraska
Press.

Fridlund, A. J., & Cacioppo, J. T. (1986). Guidelines for human electromyographic
research. Psychophysiology, 23, 567-589.

Frijda, N. H. (1986). The emotions. New York: Cambridge University Press.

Globisch, J., Hamm, A., Schneider, R., & Vaitl, D. (1993). A computer program for
scoring reflex eyeblink and electrodermal responses written in Pascal.
Psychophysiology, 39, S30.

Haffner, S. M., Mitchell, B. D., Stem, M. P., Hazuda, H. P., & Patterson, J. K. (1990).
Decreased prevalence of hypertension in Mexican-Americans. Hypertension, 16,
225-34.

Hawk, L. W. & Cook, E. W. (1997). Affective modulation of tactile startle.
Psychophysiology, 34, 23-31.

Hunt, W. A., & Clarke, F. M. (1937). The startle pattern in children and identical twins.
Journal ofExperimental Psychology, 21, 359-362.

Izard, C. (1977). Human emotions. New York: Plenum Press.

Johnson, L. C. & Corah, N. L. (1963). Racial differences in skin resistance. Science, 139,
766-767.

Johnson, L. C. & Landon, M. M. (1965). Eccrine sweat gland activity and racial
differences in resting skin conductance. Psychophysiology, 1, 322-329.

Juniper, K. & Dykman, R. A. (1967). Skin resistance, sweat gland counts, salivary flow
and gastric secretion: Age, race, and sex differences, and intercorrelations.
Psychophysiology, 4, 216-222.

Konorski, J. (1967). Integrative activity of the brain: An interdisciplinary approach.
Chicago: University of Chicago Press.

Lang, P. J. (1993). The three system approach to emotion. In N. Birbaumer & A. Ohman
(Eds), The Organization of Emotion (pp. 18-30). Toronto: Hogrefe-Huber.









Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (1990). Emotion, attention, and the startle
reflex. Psychological Review, 97, 377-395.

Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (1998). Emotion, motivation, and anxiety:
Brain mechanisms and psychophysiology. Biological Psychiatry, 44, 1248-1263.

Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (2001). International affective picture
system (IAPS). National Institutes of Mental Health (NIMH) Center for the Study
of Emotion and Attention. University of Florida, Gainesville, FL.

Lang, P. J., Greenwald, M. K., Bradley, M. M., Hamm, A. 0. (1993) Looking at pictures:
Affective, facial, visceral, and behavioral reactions. Psychophysiology, 30, 261-
273.

Leary, M. R. (1983). Social anxiousness: The construct and its measurement. Journal of
Personality Assessment, 47, 66-75.

Leary, M. R., Koch, E. J., & Hechenbleikner, N. R. (2001). Emotional responses to
interpersonal rejection. In M. R. Leary (Ed.), Interpersonal Rejection (pp.145-166).
New York: Oxford University Press.

Lipp, 0. V., Neumann, D. L., Pretorius, N. R., & McHugh, M. J. (2003). Attentional
blink modulation during sustained and after discrete lead stimuli presented in three
sensory modalities. Psychophysiology, 40, 285-290.

Malmo, R. B. (1965). Physiological gradients and behavior. Psychological Bulletin, 64,
225-34.

Matsumoto, D. (1990). Cultural similarities and differences in display rules. Motivation
and Emotion, 14, 195-214.

Matsumoto, D. (1993). Ethnic differences in affect intensity, emotion judgments, display
rule attitudes, and self-reported emotional expression in an American sample.
Motivation and Emotion, 17, 107-123.

Matsumoto, D., Kudoh, T., Scherer, K., & Wallbott, H. (1988). Emotion antecedents and
reactions in the U.S. and Japan. Journal of Cross-Cultural Psychology, 19, 267-
286.

Neuberg, S. L., & Newsom, J. T. (1993). Personal need for structure: Individual
differences in the desire for simpler structure. Journal of Personality and Social
Psychology, 65, 113-131.

Pappas, P., Gergen, P. J., & Carroll, M. (1990). Hypertension prevalence and the status of
awareness, treatment, and control in the Hispanic Health and Nutrition
Examination Survey (HHANES), 1982-84. American Journal of Public Health, 80,
1431-1436.









Popova, N. K., Barykina, N. N., Plyusnina, T. A., Alekhina, T. A., Kolpakov, V. G.
(2000). Expression of the startle reaction in rats genetically predisposed towards
different types of defensive behavior. Neuroscience and Behavioral Physiology, 30,
321-325.

Scherer, K., Matsumoto, D., Wallbott, H., & Kudoh, T. (1988). Emotional experience in
cultural context: A comparison between Europe, Japan, and the U.S.A. In K.
Scherer (Ed.), Facets of emotion: Recent research. Hillsdale, NJ: Erlbaum.

Vasey, M. W., & Thayer, J. F. (1987). The continuing problem of false positives in
repeated measures ANOVA in psychophysiology: A multivariate solution.
Psychophysiology, 24, 479-186.

Vrana, S. R. (1994). Startle reflex response during sensory modality specific disgust,
anger, and neutral imagery. Journal ofPsychophysiology, 8, 211-218.

Vrana, S. R., Spence, E. L., & Lang, P. J. (1988). The startle probe response: A new
measure of emotion? Journal ofAbnormal Psychology, 97, 487-491.

Willott, J. F., Tanner, L., O'Steen, J., Johnson, K. R., Bogue, M. A., & Gagnon, L.
(2003). Acoustic startle and prepulse inhibition in 40 inbred strains of mice.
Behavioral Neuroscience, 117, 716-727.

Winkleby, M. A., Fortmann, S. P., & Rockhill, B. (1993). Health-related risk factors in a
sample of Hispanics and whites matched on sociodemographic characteristics. The
Stanford Five-City Project. American Journal ofEpidemiology, 137, 1365-1375.















BIOGRAPHICAL SKETCH

Kathryn Gray was born on February 27, 1976, in Springfield, OH. She has been a

resident of Florida since 1978, graduating from Palm Bay High School in Melbourne, FL,

in 1994. In 1998, she earned a Bachelor of Science in psychology from the University of

Central Florida in Orlando. After three and a half years of working in the "real world,"

she decided to pursue graduate training and entered the social psychology program at the

University of Florida. In 2004, she earned a Master of Science in psychology

(specializing in social psychology) and a minor in research and evaluation methodology

from the University of Florida.