Effects of amount of food reinforcement on fixed-interval-induced attack in pigeons

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Effects of amount of food reinforcement on fixed-interval-induced attack in pigeons
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Thesis (Ph. D.)--University of Florida, 1989.
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Includes bibliographical references (leaves 94-101).
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by Raymond C. Pitts.
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EFFECTS OF AMOUNT OF FOOD REINFORCEMENT ON
FIXED-INTERVAL-INDUCED ATTACK IN PIGEONS



















By

RAYMOND C. PITTS


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


1989












ACKNOWLEDGEMENTS


I would like to thank the members of my supervisory

committee, Drs. E. F. Malagodi, M. N. Branch, B. A. Iwata,

H. S. Pennypacker, D. J. Stehouwer, and W. D. Wolking, for

all their committee-related behavior. I also want to thank

Kevin Jackson, Ron Allen, Anne Sicignano, and Jeff Kupfer

for their conceptual input. Special thanks go to Dr.

Malagodi for serving as my chair, my advisor, my teacher,

and my friend. Also, I would like to extend my appreciation

to Dr. Branch for the generous use of his computer

equipment. Finally, very special thanks go to the most

important person in my life, Christine Hughes, for helping

me in every possible way.















TABLE OF CONTENTS


ACKNOWLEDGEMENTS . . .

ABSTRACT . . .

GENERAL INTRODUCTION . .
Literature Review . .
The effects of schedule variables on induced


behavior . .
The effects of consequence variables on
induced behavior . .
Summary and conclusions .
Theoretical Overview . .
Falk's adjunctive behavior hypothesis .
Notions that schedules possess aversive


properties . .
Staddon's motivational hypothesis
Killeen's concept of arousal .
Summary and conclusions .
The Purpose of the Present Experiment


EXPERIMENT 1 .
Introduction .
Method . .
Subjects ..
Apparatus .. ..
Procedure .
Results and Discussion .

EXPERIMENT 2 .
Introduction .
Method . .
Subjects .
Apparatus .
Procedure. .
Results and Discussion .

GENERAL DISCUSSION .

REFERENCES . .


. 4

. 8
. 10
. 11
. 11


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. . 26
. . 28
. . 28
. . 28
. . 30
. 33

. . 59
. . 59
S. . 60
. . 60
. . 61
. .. 61
. ....... 62

. . 75

. .. 94


102


BIOGRAPHICAL SKETCH .




iii


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Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

EFFECTS OF AMOUNT OF FOOD REINFORCEMENT ON
FIXED-INTERVAL-INDUCED ATTACK IN PIGEONS

By

RAYMOND C. PITTS

December, 1989

Chair: Dr. E. F. Malagodi
Major Department: Psychology

Keypecking by pigeons was maintained on a chained

fixed-interval t fixed-ratio one schedule of food

presentation. Attacks toward a restrained and protected

conspecific were recorded. In the first experiment, the

amount of food presented per interval was manipulated across

phases by varying the number of repetitions of the fixed-

ratio one schedule required in the terminal component of the

chain. Levels of attack during the fixed-interval component

increased monotonically as a function of amount of food

presented in the terminal component. In the second

experiment, a multiple schedule was used in which two

different food amounts alternated within each session. For

both pigeons in this experiment, more attack was observed

during the component that delivered the larger amount of





food per interval. The results of these experiments are

discussed in terms of a number of different theoretical

frameworks, including views that attack is properly

considered as "adjunctive behavior," notions that

intermittent schedules possess aversive properties,

conceptualizations of attack as an example of "interim

activities," concepts that suggest that induced attack

results from "arousal," and suggestions that induced

behaviors can be conceptualized within the context of an

"opponent-process" theory of motivation. It is suggested

that, although the results of the present study are relevant

to each of these views, further analyses are required before

an integrated picture of induced attack and other induced

behaviors can emerge.














GENERAL INTRODUCTION


Since Ferster and Skinner's (1957) extensive survey of

schedules of reinforcement, numerous empirical studies and

theoretical discussions of the effects of various schedules

have been published by other investigators (see Zeiler, 1977

for a review). Indeed, it may be said that the study of

reinforcement schedules became the dominant research area in

the experimental analysis of behavior during the next two or

three decades. The primary focus of these empirical and

theoretical analyses has been examination of the effects of

schedule variables on rates and temporal patterns of ongoing

operant behavior maintained by intermittently presented

reinforcers.

Some experimenters studying intermittent schedules,

however, began to notice that powerful and ubiquitous

"schedule-effects" were not restricted to behaviors which

produced, or closely preceded, the scheduled reinforcer.

Falk (1961), for example, discovered a most interesting and

reproducible sequence of behavior in rats when lever

pressing was maintained by a variable-interval (VI) schedule

of food presentation. Rates and patterns of lever pressing







2

were typical for VI schedules in that a moderate and steady

rate of responding was maintained. In addition to lever

pressing, and eating the food pellets as they were

delivered, the rats regularly drank from a water bottle that

was continuously available in the chamber. While it was not

especially surprising that the rats drank from the bottle

during lengthy experimental sessions, a number of

characteristics of drinking were unexpected, yet were quite

orderly. The features of drinking (and of the conditions

under which drinking occurred in this experiment) that

captured Falk's attention and became the focus of a large

number of subsequent experiments were a) while the rats were

food-deprived, they were not water-deprived, b) drinking

followed each and every delivery of a food pellet, c) the

rats consumed excessive amounts of water--approximately four

times the amounts normally consumed per twenty-four hour

period in the home cages, and d) drinking decreased

dramatically or ceased altogether during various "control"

procedures during which food was not intermittently

scheduled. Subsequent experiments determined that such

"adjunctive" or schedule-induced drinking could not be

viewed as superstitious behavior controlled by accidental

reinforcement of licking by food presentation (see Falk,

1971).

In a related experiment, Gentry (1968) demonstrated

that when keypecking by food-deprived pigeons was maintained









on a fixed-ratio (FR) schedule of food presentation, the

pigeons reliably attacked a restrained conspecific located

at the rear of the experimental chamber. The attacking

observed by Gentry (1968) was similar to the drinking

observed by Falk (1961) in that attacking a) was typically

observed to occur in periods just after food delivery,

b) followed a large proportion of food presentations, c) did

not occur under conditions when food was not intermittently

presented, and d) apparently was not adventitiously

reinforced by food presentation. In both Falk's (1961) and

Gentry's (1968) experiments, a regular temporal sequence of

behavior was observed: following delivery of food, the

subjects engaged in a bout of induced activity (pigeons'

attacking and rats' drinking) which ceased rather abruptly

and was followed by operant behavior (pigeons' keypecking

and rats' lever pressing) until the next food delivery.

A rather wide range of other induced behaviors has been

found to occur following food presentation during various

intermittent schedules of reinforcement. These include pica

in rats and monkeys, aggression in monkeys, wheel-running in

rats, drinking in pigeons, escaping from stimuli associated

with positive reinforcement in pigeons and rats, and air

licking in rats (see Falk, 1971; Staddon, 1977;

Wetherington, 1982). Investigations over the past 25 years

have shown that these schedule-induced behaviors occur in

several species, are induced by a variety of intermittent








schedules, and are induced by various events (e.g., food,

water, and shock) when scheduled intermittently.



Literature Review

Much of the research on schedule-induced behavior can

be divided into two general categories: a) experiments

investigating the effects of schedule variables, such as

parameter value of a given schedule or schedule type, and b)

experiments investigating the effects of variables

associated with the scheduled event itself, or what might be

called consequence variables. Included in this class of

variables are deprivation of, and amount of the scheduled

reinforced.

The effects of schedule variables on induced behavior

Most experiments in this category have focused on

examination of induced behavior as a function of schedule

parameter, such as the interfood interval on time-based

schedules, or the response requirement on ratio schedules.

The relationship between induced behavior and interfood

interval on time-based schedules depends upon the particular

induced behavior and on its measurement. In studies of

induced drinking during fixed-interval (FI), variable-

interval (VI), and fixed-time (FT) schedules of food

presentation, total water consumption is an inverted U-

shaped function of the interfood interval (Bond, 1973; Falk,

1966; Flory, 1971; Hawkins, Shrot, Githens, & Everett, 1972;








Wetherington, 1979). This inverted U-shaped, or bitonic,

function relating induced drinking to interfood interval has

also been reported with the number of licks per session

(Flory, 1971; Wetherington, 1979), the amount of time

drinking per pellet (Wetherington, 1979), and the percentage

of intervals containing drinking (Allen & Kenshalo, 1976;

Segal, Oden, & Deadwyler, 1965). However, when drinking

induced by an FT schedule of food presentation is measured

as the rate of water consumption and as the rate of licking,

both are a decreasing function of interfood interval

(Wetherington, 1979). These differences in relations

between drinking and interfood interval as a function of

measurement illustrate the importance of measurement

selection, its effects on experimental results, and on

theoretical interpretations derived from them. For detailed

discussions of measurement issues in schedule-induced

behavior, see Allen, Sicignano, Webbe, & Malagodi (1980),

Webbe, DeWeese, & Malagodi (1974), and Wetherington (1979,

1982).

Results of experiments examining induced attack as a

function of interfood interval are more consistent across

measures than those of induced drinking. Attack by pigeons

induced by FI, FT, and response-initiated FI schedules of

food presentation show a bitonic relation to interfood

interval similar to that seen with induced drinking (Cherek,

Thompson, & Heistad, 1973; DeWeese, Webbe, & Malagodi, 1972;








Flory, 1969b). This bitonic function was observed with all

measures of induced attack employed in these experiments,

which included rate of attack, attacks per reinforcement,

percent of intervals with attack.

Schedule-induced "escape" by pigeons has also been

observed during fixed-interval schedules of food

presentation (Brown & Flory, 1972). In this experiment,

pecks on one key produced food according to an FI schedule,

while pecks on a second key produced an "escape" period with

a visual stimulus change. These investigators reported a

bitonic relation between measures of escape (escape rate and

percent of session during escape stimuli) and interfood

interval for most subjects. Note, however, that the fixed-

interval timer did not operate during the stimulus change

periods and, thus, these periods may not have functioned as

true escape periods.

The effects of ratio parameter on schedule-induced

behavior most often has been examined in studies of induced

attack in pigeons and monkeys, and induced escape in pigeons

and rats. As with studies on induced drinking during time-

based schedules, the results of experiments on the effect of

ratio size on induced attack depend critically upon how

attack is measured. When induced attack is examined in

fixed-ratio (FR) (Flory, 1969a; Hutchinson, Azrin, & Hunt,

1968; Knutson, 1970; Webbe et al., 1974), variable-ratio

(VR) (Webbe et al., 1974), and regressive-ratio (Reg R)







(Allen et al., 1980) schedules of food presentation, most

measures tend to increase monotonically as a function of

ratio size. These measures include total number of attacks

(Hutchinson et al., 1968; Knutson, 1970), total number of

attack episodes (Flory, 1969a), time spent attacking

(Knutson, 1970), attacks per interval (Webbe et al., 1974),

and proportion of intervals containing attack (Flory, 1969a;

Webbe et al., 1974). However, when rate of mirror-pecking

is measured as a function of ratio size in FR schedules of

food presentation, an inverted U-shaped function is observed

(Cohen & Looney, 1973).

When keypecking or lever pressing is maintained on

ratio schedules of food presentation, pigeons and rats will

respond on a second operandum when these responses produce

escape, or time-out, periods. During these escape periods,

responses usually do not count toward the completion of the

ratio requirement. Subjects escape more frequently,

following more food presentations, and spend more time in

time-out periods as a function of ratio size in FR and

progressive-ratio (PR) schedules (Appel, 1963; Azrin, 1961;

Dardano, 1973; Thompson, 1964).

Relatively few studies have examined induced polydipsia

under ratio schedules of food presentation. Total water

intake and total licks are an increasing function of the

response requirement on FR schedules (Burks, 1970; Carlisle,

1971). Note that, unlike studies of induced attack and








induced escape, the effects of ratios of over 100 have not

been examined in studies of induced drinking.

The effects of consequence variables on induced behavior

The literature relating consequence variables to

schedule-induced behavior is less extensive than the

literature on schedule variables. Data on consequence-

variable effects have come nearly exclusively from

experiments on schedule-induced polydipsia in rats.

Published reports of examinations of these variables on

other induced behaviors and in other species are

conspicuously lacking.

When studied as a function of food deprivation, induced

drinking is usually an inverse function of body weight

(e.g., Falk, 1969; Freed & Hymowitz, 1972; Roper & Nieto,

1979; Wayner & Rondeau, 1976). One study examining the

effect of this variable on schedule-induced attack in

pigeons reported a similar inverse relation (Dove, 1976).

A number of studies have examined the relation between

induced drinking and the amount (or magnitude) of food

reinforcement. A majority of these experiments have

reported increases in measures of induced drinking as a

function of food amount (e.g., number of pellets) (Bond,

1973; Couch, 1974; Flory, 1971; Hawkins et al., 1972;

Rosellini & Burdette, 1980; Yoburn & Flory, 1977). Some

studies, however, have found that induced drinking decreases

(Falk, 1967; Freed & Hymowitz, 1972) or does not change







systematically as a function of food amount (Keehn &

Colotla, 1971). One set of experiments reported that the

effects of amount of food reinforcement on schedule-induced

drinking depended upon whether comparisons were made within

or between experimental sessions (Reid & Dale, 1983; Reid &

Staddon, 1982). Larger amounts of food attenuated drinking

when comparisons were made within sessions, but augmented

drinking when comparisons were made between sessions.

Issues surrounding measurement of induced behavior are

not only important in examinations of schedule variables,

but are also important in experiments on food amount. Falk

(1967) reported that when lever pressing was maintained on a

VI-1 min schedule of food presentation, two pellets per

interval resulted in lower total water intakes than did one

pellet per interval. However, in this experiment, the

number of pellets per session was constant across

conditions, resulting in shorter sessions and fewer

intervals per session during the two-pellet condition. When

these data were recalculated as ingestion rates, drinking

was higher during the two-pellet condition in four of six

possible comparisons (Hawkins et al., 1972).

The relation between schedule-induced attack and the

amount of food has not been extensively studied. One

investigation found that the larger of two food magnitudes

induced more attack in pigeons when food was presented on FT

schedules (Flory, Robinson, & Dunahoo, 1988). Investigations






10

of induced attack as a function of a range of reinforcement

amounts have not been reported.

Summary and conclusions

As mentioned above, the effects of schedule

manipulations depend upon the particular induced response

studied and upon how that response is measured. In general,

however, most experiments relating induced drinking and

induced attack to interfood interval on time-based schedules

of food presentation have revealed an inverted U-shaped, or

bitonic, function. In contrast, most experiments of induced

behavior during ratio schedules have shown monotonically

increasing levels of induced responding as a function of

ratio parameter. The exceptions to these general findings

are usually when rates of induced behavior are used as

dependent variables (see section entitled The effects of

schedule variables on induced behavior).

The effects of consequence variables have usually been

studied on induced polydipsia in rats. In general, levels

of behavior induced by intermittent schedules of food

presentation increase as a function of deprivation level and

as a function of food amount, although a few studies have

reported contrasting effects of food amount.

It is tempting to conclude that the data reviewed above

on consequence variables imply that operations that increase

the reinforcing efficacy of the scheduled event result in

increases in levels of induced activity. It is contended








here that such a conclusion would be premature. More

systematic and comprehensive analyses of the effects of

consequence variable on different induced behaviors, in

different species, and in different schedule contexts must

be undertaken in order to provide a more complete

characterization of the effects of these variables on

schedule-induced behavior.



Theoretical Overview

Several theoretical frameworks have been offered in

attempts to clarify the nature of the processes involved in

schedule-induced behavior. These include 1) the adjunctive

behavior hypothesis proposed by Falk, 2) the view that

intermittent schedules possess aversive properties, 3)

Staddon's motivational hypothesis, and 4) Killeen's concept

of arousal. These views differ markedly in their structure

and in specific predictions derivable from them and,

therefore, will be discussed separately and in detail.

Falk's adiunctive behavior hypothesis

One conceptualization of schedule-induced behavior was

proposed by Falk (1969, 1971). When early attempts to

reconcile the excessiveness of induced polydipsia with known

regulatory mechanisms failed, attention turned toward it's

environmental determinants. Difficulties in the application

of principles of operant or respondent conditioning as

explanations of induced behavior led Falk (1971) to propose








the existence of a new class of behavior. Noting a number

of similarities among induced activities (discussed above),

Falk suggested that schedule-induced drinking, schedule-

induced attack, and other schedule-induced activities are

properly considered members of a class of "adjunctive"

behaviors. These behaviors are adjunctive in that they

occur as by-products of a schedule of reinforcement that

maintains some other response, and are considered similar to

the displacement activities observed and discussed by

ethologists. Displacement activities are described as

occurring in situations where an animal "under high drive

conditions" is engaged in some sort of consummatory behavior

and is prevented from continuing this behavior (Falk, 1971).

Falk points out that these are the conditions producing

adjunctive behavior: a food deprived animal engaged in

eating is prevented from continuing this behavior by the

imposed intermittent schedule of food presentation.

The bitonic function frequently observed in studies

relating induced responding to schedule parameter is central

to Falk's interpretation. He proposes that intermittent

presentation of food results in adjunctive behavior only

when the schedule arranges a rate of food consumption within

a certain "effective range." This consummatoryy rate

hypothesis" suggests that at high rates of food consumption

(e.g., short interfood intervals) adjunctive responding is

low. As consumption rate decreases (e.g., by lengthening






13

the interfood interval), adjunctive behavior increases to a

maximum until, at still lower consummatory rates, adjunctive

behavior decreases (Falk, 1969, 1971). According to this

view, the particular type of schedule is important only

insofar as it arranges a particular consummatory rate.

Data from those experiments demonstrating a bitonic

function between rate of food presentation and measures of

induced behavior, coupled with the similarities among

induced activities listed earlier provide evidence in favor

of Falk's view. In addition, Falk (1967) compared various

combinations of interfood intervals and food amounts that

programmed equal consummatory rates (e.g., VI 1 min with one

food pellet per interval and VI 2 min with 2 pellets per

interval), and reported that the most reliable predictor of

the total amount of schedule-induced drinking was the number

of pellets presented per minute (Falk, 1967). However,

different session lengths (and hence, different total

interfood intervals per session) were programmed during

conditions that delivered two pellets. This feature

severely handicaps definitive interpretation of these data

(see General Discussion for a more detailed discussion of

this study and the consummatory rate hypothesis).

Some studies, however, have reported data that are at

odds with Falk's consummatory rate hypothesis. First, FR

schedules have been found to induce more attack than

response-independent schedules that program equal rates and






14

temporal distributions of food presentation (i.e., matched-

time, or MT schedules) (Malagodi, Sicignano, & Allen, 1979).

Second, some studies of induced drinking (Bond, 1973) and

induced attacking (Flory et al, 1988), comparing various

combinations of interfood intervals and food amounts have

failed to replicate Falk's (1967) results. Third, a number

of studies have reported direct, monotonic increases in

schedule-induced attack, escape, and polydipsia as a

function of ratio size (See Literature Review). Falk

(1971), has noted that data reported in studies on ratio

schedules may represent only the ascending portion of the

bitonic function relating adjunctive behavior to interfood

interval (the descending portion if food rate is used as the

independent variable). However, subsequent data obtained on

regressive-ratio (Reg R) schedules have reported a

monotonically increasing function between schedule-induced

attack and ratio size, even when interfood intervals on the

larger ratios (over 100 minutes) far exceeded those

previously shown to produce the descending portion of the

bitonic function (Allen et al., 1980). The results of the

experiments discussed above suggest that factors other than

consummatory rate per se are important in the production and

maintenance of schedule-induced behavior.








Notions that schedules possess aversive properties

A second interpretation of schedule-induced behavior

(particularly schedule-induced attack and escape) is offered

by Azrin and his associates (Azrin, 1961; Azrin, Hutchinson,

& Hake, 1966; Hutchinson et al., 1968), and others (Richards

& Rilling, 1972). The results of studies showing a direct

relation between attack and response requirement in ratio

schedules, in concert with data showing that attack is often

generated by conditions that are normally escaped or

avoided, such as electric shock presentation (Azrin,

Hutchinson, & McLaughlin, 1965; Ulrich & Azrin, 1962), a

physical blow (Azrin, Hake, & Hutchinson, 1965), and

extinction (Azrin et al., 1966; Kelly & Hake, 1970), suggest

that intermittent schedules may possess aversive properties.

In this view, periods of zero or low reinforcement

probability in intermittent schedules are aversive, and the

magnitude of aversiveness is partly determined by the

response requirements of ratio schedules (Hutchinson et al.,

1968). This interpretation is supported by studies showing

that subjects will escape from schedules of positive

reinforcement, that likelihood of escape is directly related

to ratio size (Azrin, 1961; Appel, 1963; Thompson, 1964) and

that more attack is induced by FR schedules than by MT

schedules (Malagodi et al., 1979). Further support of this

view derives from data that have reported more induced

attack under an FR schedule of food presentation than under








an equal valued VR schedule (Webbe et al, 1974). The

occasional reinforcements that closely follow previous

reinforcement periods on VR schedules might attenuate the

aversiveness of the post-reinforcement periods.

Although the notion that intermittent schedules possess

aversive properties is compelling, data from some studies

suggest that factors other than schedule aversiveness are

involved in schedule-induced attack and in other schedule-

induced behaviors. The bitonic relation frequently observed

with induced behavior during time-based schedules and

occasionally observed during ratio schedules is difficult to

reconcile with the notion of schedule aversiveness. This

relation suggests either an entirely different

interpretation, or an amendment that addresses the

decreasing portion of the function at longer interfood

intervals. For example, it is possible that the ascending

portion of the bitonic function on time-based schedules

results from an increase in schedule aversiveness, and the

decrease in this function at longer intervals reflects

competition from other activities that emerge at these

longer intervals (e.g., the "facultative activities"

proposed by Staddon, 1977).

Staddon's motivational hypothesis

A third theoretical approach has been offered by

Staddon and his colleagues (Staddon, 1977; Staddon & Ayers,

1975; Staddon & Simmelhag, 1971). According to this







conceptualization, much of the research on schedule-

controlled behavior has been governed by the tacit

assumption that the effects of response-dependent

reinforcement are somehow more fundamental than those of

response-independent reinforcement. In Staddon's (1977)

view, correlations between reinforcement, and temporal and

stimulus variables are most important in determining the

final pattern of performance on reinforcement schedules. If

the way these variables act is to be understood, the

response contingency so ubiquitous in operant conditioning

experiments is an unnecessary complication. Therefore, most

of the data offered in support of this position are from

studies using response-independent food presentation.

Staddon (1977) notes that periodic (and therefore

intermittent) presentation of response-independent food

results in an organized and stereotyped sequence of behavior

(termed "schedule-induced behavior"). In this framework,

adjunctive (or schedule-induced) and operant responses are

all classified as schedule-induced behavior, with the

distinction between them being their temporal location

within the interfood interval. For Staddon, induced

behaviors that emerge in the presence of, or are directed

toward, stimuli that are predictive of food are called

"terminal responses" and are what is traditionally studied

as operant behavior. Induced behaviors that emerge at times

when food is unlikely are called "interim responses" and are








what is traditionally studied as adjunctive or schedule-

induced behavior. Thus, when intermittent reinforcement is

programmed, observed keypecking by pigeons and lever

pressing by rats are considered terminal responses, and

schedule-induced attacking in pigeons and drinking in rats

are considered interim responses. Each type of activity is

seen as serving an adaptive function: terminal responses are

related to the procurement and consumption of food, and

interim responses serve to remove an animal from food

situations at times when food is unlikely. Interim

responses include schedule-induced drinking and attacking,

and any number of activities observed to occur during the

period shortly after food delivery (e.g., grooming,

preening, wing flapping) (Staddon & Simmelhag, 1971).

Staddon (1977) suggests that all induced activities are

critically dependent upon motivational factors. Two types

of motivational variables are said to determine induced

behavior: variables related to the scheduled reinforcer

(e.g., deprivation, schedule, and amount) and variables

related to the particular interim response (e.g., "thirst"

if drinking is the interim response). In studies on

schedule-induced polydipsia, for example, induced drinking

and food related responding (such as lever pressing) are

related to food motivation in a similar way: ". the

'hungrier' the animal during the terminal period, the

'thirstier' he is during the interim period" (Staddon, 1977,








p. 139). Thus, programming intermittent food presentation

to a food-deprived rat is a motivational operation similar

to depriving the rat of water and results in drinking at

times when food delivery is unlikely. In this view, any

operation that increases the reinforcing efficacy of food

should similarly increase both terminal and interim

responding, until a point is reached where the two

activities are in direct competition, at which time the

entire interfood interval is dominated by the terminal

response.

Staddon (1977) cites examples in which schedule-induced

drinking is a direct function of food rate and food amount

in support of his motivational hypothesis (see Literature

Review). Also presented are data replotted from Falk (1969)

and Flory (1971), originally reporting bitonic functions

relating total water intake to interfood interval. When

these data are plotted as water intake per minute and licks

per minute as a function of food rate, both are

monotonically increasing. It is not surprising that such a

difference is seen when rate is used as a measure of induced

activity. When the number of interfood intervals per

session are constant (as is frequently the case in studies

of induced behavior), then session length is likely to

decrease as schedule parameter is decreased (this must occur

if interval schedules are used). Thus, when induced

behavior is measured as a rate, no change, or even a









decrease in total number of induced responses as schedule

parameter is decreased can actually show a rate increase due

to a decrease in size of the denominator.

Recall that a number of studies have found that many

measures of induced responding are bitonically related to

interfood interval and are directly related to ratio size.

Neither of these results is predicted from the view proposed

by Staddon. Also, recall that Staddon's approach is

predicated upon studies employing response-independent food

presentation. Indeed, it has been asserted that the

presence or absence of a response-requirement makes little

difference in the amount or temporal placement of schedule-

induced drinking (Burks, 1970; Falk, 1971; Segal et al.,

1965; Staddon, 1977). Studies of schedule-induced attack,

however, have shown that measures of attack may depend

critically upon the number of responses required for food

reinforcement (Allen et al., 1980), and that this relation

is independent of interfood interval (Malagodi et al.,

1979). These results also are not predicted from the

theoretical framework offered by Staddon (1977).

Killeen's concept of arousal

A fourth approach to schedule-induced behavior has been

outlined by Killeen (Killeen, 1975; Killeen, Hanson, &

Osborne, 1978) and suggests that these behaviors are a

normally occurring part of an organism's repertoire, but

"their rate of occurrence is excited to supernormal levels








by a heightened level of arousal" (Killeen et al., 1978, p.

571). This excessive arousal is produced by the periodic

delivery of food (or other "incentives"), and each delivery

contributes a small amount of arousal. With repeated

deliveries, the arousal accumulates to a stable,

"equilibrium," level that depends upon the size of the

arousal, its rate of decay, and the time interval between

arousal impulses.

Killeen's concept of arousal has been operationalized

as measurements of "activity" taken by a set of

microswitches located under floor panels of a standard

pigeon operant-conditioning chamber. When food-deprived

pigeons were exposed to fixed-time (FT) schedules of grain

presentation at various interfood intervals, a specific

pattern of activity within each interval was observed. Low

levels of activity occurred immediately following food

presentation, increased rather rapidly to a maximum at about

one-quarter of the way into the interval, then gradually

returned to low levels by the end of the interval (Killeen,

1975; Killeen et al., 1978). The overall amount of activity

was an increasing function of food rate, although the

general pattern of activity within each interval was similar

at all rates.

Killeen et al. (1978) provide a mathematical model of

arousal which suggests that the general pattern of activity

observed when food is intermittently presented results from








the interaction of three processes: The first process is

"arousal," which is maximal immediately after food

presentation and decays very gradually throughout the

interfood interval. The second process is termed "post-

prandial inhibition" (". post-prandial behaviors and

quiescence elicited by the offset of the previous incentive

or the offset of a conditioned stimulus that indicates the

immediate unavailability of other incentives." p. 372).

Post-prandial inhibitions are maximal just after food

presentation, and decay very rapidly. They compete with

arousal and result in the low levels of activity observed

just after food delivery; the rapid rise in activity is the

result of the rapid decay in these inhibitions coupled with

an existing high level of arousal. The third process is

competition from terminal behaviors (such as keypecking or

approaching the food hopper); competition from these

terminal behaviors grows with the passage of time in the

interfood interval, and results in an exponential decay of

activity across the interval.

Killeen et al. (1978) suggest that if the time

between food presentations is short enough, arousal

accumulates to such an extent that the "excessive" character

of schedule-induced behavior is observed. This model also

predicts a proportionality between activity (including

schedule-induced behaviors) and rate of food presentation

(Killeen et al., 1978). This prediction is confirmed in








some studies of activity (Killeen, 1975; Killeen et al.,

1978) and of schedule-induced behavior (Killeen, 1975;

Wetherington, 1979). Results of studies that show a bitonic

relation between schedule-induced behavior and interfood

interval are not predicted from Killeen's model, nor are

those that show a direct relation between induced behavior

and ratio size. Killeen's model also predicts that other

variables which increase arousal should also increase levels

of schedule-induced behavior. For example, more arousal is

expected to result from increased food deprivation and from

presentation of larger amounts of food. With a few

exceptions, these predictions are generally confirmed by the

data on consequence variables (see Literature Review).

Summary and conclusions

It must be noted at this point that the four viewpoints

presented above are not offered as an exhaustive list of

interpretations of schedule-induced behavior. However, they

represent four of the most popular and most cited

theoretical conceptualizations in this research area. Other

hypotheses, such as notions that induced behaviors are

adventitiously reinforced by food presentation, or views of

induced drinking as resulting from dry-mouth, have not

survived experimental analyses (see Staddon, 1977).

The theoretical positions reviewed above suggest

different relationships between induced behavior and

schedule and consequence parameters. These viewpoints focus








on different induced activities, emphasize different

characteristics of induced behavior, and rely upon different

measurement procedures. Each of these conceptualizations

are supported by results from some experiments but not by

others. Thus, given the differences among these views, and

given the disparities in experimental data, it becomes

difficult to decide which of these views, or combination of

views, is the most effective available account of schedule-

induced behavior. The view taken here is that, although an

extensive literature exists in schedule-induced behavior,

not enough data are available to make conclusions regarding

these, or any other, theoretical interpretations. Further

analyses along a number of dimensions are required before

useful theoretical statements about schedule-induced

behavior can be made. For example, a complete picture of

the effects of ratio size on induced drinking is lacking.

The effects of relatively large ratios must be studied to

determine whether the descending portion of the bitonic

function so often observed at long interval durations is

obtained. Also lacking are data on the effects of

consequence variables on induced behaviors other than

drinking. The absence of comprehensive analyses of these

variables on induced attack and induced escape severely

handicaps attempts at theoretical integration.








The Purpose of the Present Experiment

The relative paucity of data on the effects of

consequence variables on induced behaviors other than

drinking is surprising, especially in view of a tradition of

interspecies and interresponse replication among experiments

on schedule variables. Systematic examinations of the

relationship between the amount of food reinforcement and

schedule-induced attack are noticeably absent. Therefore,

the purpose of the present set of experiments is to provide

a characterization of the function relating the amount of

food reinforcement to schedule-induced attack over a

relatively wide range of reinforcement amounts. It is hoped

that data from these experiments will fill gaps in the

existing literature and help provide an empirical basis for

an eventual formulation of an adequate theoretical

integration of schedule-induced phenomena.














EXPERIMENT 1


Introduction

In Experiment 1, the amount of food was systematically

manipulated across phases. Keypecking in pigeons was

maintained by a two-component chained schedule of food

presentation; the first component was an FI schedule and the

second component was an FR 1 x n schedule. In the second

component, completion of each FR 1 produced food. The

amount of food per interval was examined by manipulating the

number of consecutive FR l's (n) in the second component.

The particular schedule of food presentation used in

this experiment was selected for three reasons. First, an

FI schedule was employed in hopes of generating intermediate

levels of attack and, thus, providing a sensitive baseline

against which to assess the effects of food amount. Ratio

schedules of food presentation generally induce greater

amounts of attack than do time-based schedules (Malagodi et

al., 1979). Employing a ratio schedule in the present

experiment may have resulted in near ceiling levels of

attack and, therefore, may have masked the effects of food

amount. Second, amount of food was varied by programming

repeated FR l's in the terminal component, during which the






27

food hopper was raised for fixed durations. This procedure

was used, rather than simply raising the food hopper for

varying durations, partly because of the capacity of the

hopper. Because there was no a priori determination of the

maximum food amount to be investigated, the possibility

existed that, at very long hopper durations, the pigeons

would empty the hopper prior to the end of the reinforcement

cycle. Programming FR 1's allowed the hopper to refill

during the periods it was lowered. Also, the function

relating amount of food consumed by pigeons to hopper

duration may not be linear, but negatively accelerated, with

an asymptote at approximately seven seconds (Epstein, 1981).

By arranging FR 1's to produce the food hopper for a fixed

duration throughout all conditions, and by varying the

number of consecutive FR 1's in the terminal component, it

was reasoned that the actual amount of food consumed would

more closely correspond to the value of the manipulated

variable. Third, a chained schedule was used so that a

distinct stimulus would be correlated with the beginning of

and, most importantly, the termination of each period of

food presentation. If, for example, a tandem rather than a

chained schedule had been used, no programmed stimulus

change would have accompanied the completion of the final FR

1 in the terminal component. Under such conditions, levels

of attack may have been influenced by a tendency to peck the

key during the early portions of the fixed-interval.










Method

Subjects

Three adult male White Carneau pigeons (Columba livia),

P-5626, P-7848, and P-1313 served as experimental subjects.

Pigeons P-5626 and P-7848 had previous experience keypecking

on concurrent VI schedules of food presentation. Pigeon P-

1313 had a history of keypecking under VR and VI schedules

of food presentation. Each subject was randomly paired with

another bird that served as its target. Each bird was

individually housed with water and health grit continuously

available. Experimental subjects were maintained at

approximately 80% of their free-feeding body weights. Food

was continuously available for the target birds.

Apparatus

A 36 x 40 x 27 cm experimental space was enclosed in a

sound-attenuating chamber. One wall was fitted with a

standard BRS-Foringer three-key stimulus panel. The right

key, located 8 cm from the right wall, could be

transilluminated either white or red. Pecks with a force of

at least 0.19 N against this key were defined as responses.

The other two keys were dark and inoperative during this

experiment. Two white houselights, each 10 cm from a side

wall and 7 cm apart, were located above the stimulus panel.

One white houselight was placed at the center of the back

wall. A 4.5 x 5.5 cm aperture, into which a food hopper








could be raised, was located 15 cm below the center key.

Reinforcement consisted of 4 s access to mixed grain, during

which the houselights and keylight were turned off and a

white light illuminated the food hopper.

The apparatus for restraining the target birds and for

recording attack was similar to that described by Azrin et

al. (1966) and Webbe et al. (1974), and was centered at the

rear of the chamber, 40 cm from the stimulus panel. The

restraint unit was a rectangular box constructed of clear

Plexiglas and was mounted on a spring loaded metal plate.

The unit was positioned with one end facing the experimental

space. A microswitch was located under the metal plate such

that displacements of the unit with a force that exceeded

1.25 N activated the microswitch and were recorded as

attacks. Visual inspection of early sessions via a video

monitor revealed that at this force requirement, movements

of the target did not activate the microswitch, but that

most of the contacts by the experimental bird were reliably

recorded.

The target bird was restrained within the unit with

foam cushions positioned below it and to its rear. An

opening on the top of the unit closest to the experimental

space allowed for the extrusion of the target bird's head,

neck, and upper breast. A bib, constructed of synthetic

white fur, was attached to the target so that the exposed

breast region was entirely covered. An inverted, U-shaped,








Plexiglas shield was mounted 3 cm in front of the target

bird's face and in the same plane as the rear wall of the

chamber. This shield was positioned so the fur-covered

breast of the target was exposed and the head of the target

was protected. This arrangement allowed contacts of

sufficient force of either the breast region or of the

shield to activate the microswitch, while safeguarding

against injury to the target bird. A diagram of the target

restraining unit is provided in Figure 1.

Continuous white noise was present to mask extraneous

sounds, and a ventilation fan provided air circulation

within the experimental space. All experimental events were

programmed and recorded by electromechanical equipment

located in a separate room.

Procedure

All experimental subjects had prior keypecking

experience, so no initial training was necessary. Each

subject was initially placed in the chamber for three one-

hour sessions with its target bird present, the white

houselights on, and no experimental contingencies in effect.

The targets were then removed and each experimental pigeon

was exposed to a chained fixed-interval t fixed-ratio 1

times n schedule of food presentation (Ch FI t FR 1 x n).

On this schedule, in the presence of a white keylight, the

first keypeck after t min had elapsed turned the keylight

red, and each of the next n keypecks produced reinforcement.







After n grain presentations the keylight turned white and

the cycle was repeated. The value of t was 4 min for P-5626

and P-1313, and was 12 min for P- 7848.1 The initial value

of n for each subject was one. After 30 sessions of fifteen

intervals each under this schedule, the targets were

reintroduced. The targets were present, and attack was

recorded, during all remaining sessions of both experiments.

Changeover contingencies were programmed such that in the

presence of the white keylight keypecks within 5-s after an

attack could not change the keylight to red, and in the

presence of the red keylight could not produce grain.

After measures (outlined below) of attack had

stabilized under the n = 1 condition, the value of n was

manipulated systematically across experimental phases. The

values of n for each subject, the order of exposure to those

values, and the number of sessions in all conditions of

Experiment 1 are shown in Table 1. Pigeons P-7848 and P-



'The FI value for P-7848 was initially 4 min. Manipulation
of n from 1 to 24 under this schedule had little effect on
measures of attack. Attack levels at all n values were
relatively high for this subject. Because many studies have
shown that attack induced by time-based schedules is
bitonically related to inter-food interval, with peak levels
often seen at intervals between 2 and 4 min (e.g. Cherek et
al., 1973; DeWeese et al., 1972; Flory, 1969b), it was
thought that attack in this subject may have been at ceiling
levels at all n values. The fixed-interval duration for
this subject was therefore increased to 12 min in hopes of
producing a more intermediate attack level, and hence a more
sensitive baseline against which to assess the effects of n.
When the interval value was increased to 12 min at an n of
1, mean attacks per interval with attack for the last 15
sessions decreased from 118.7 to 64.2.







32

5626 were exposed to an ascending series of n values from 1

to 24, in increments of 8. The effects of n = 8 and n = 16

were redetermined once for P-7848 and P-5626, respectively.

The effects of n = 1 were redetermined twice for each bird.

Pigeon P-1313 was exposed to n values of 1, 8, and 16.

After 92 sessions under the n = 16 condition this subject

was removed from the experiment because of illness.

Sessions were usually conducted 5 days per week, except

at larger values of n, when sessions were conducted every

other day to insure that the body weights of the subjects at

the beginning of each session were comparable across

experimental conditions. Sessions were also conducted every

other day during one of the exposures to n = 1 for both

birds and during the second exposure to n = 8 for P-7848.

These conditions are noted by a 1 in Table 1. Phases in

which sessions occurred every other day at lower n values

were conducted to assess the effects of n when a

manipulation in this variable was not accompanied by a

change in the schedule of sessions. Sessions terminated

following completion of the fifteenth cycle, except at large

n values, when the number of intervals per session for P-

5626 was reduced to 10 (noted by a 2 in Table 1).

Two measures of attacking served as dependent variables

in the present experiment: the number of attacks per

interval with attack and the proportion of intervals with at

least one attack. These measures capture two different








characteristics of induced attack, the former depicts the

average level of attack within an interval once attack has

been initiated, and the latter estimates the tendency to

initiate attack within a given interval. Measures such as

these have been shown to be quite sensitive to manipulations

of schedule parameter in both interval and ratio schedules

(e.g., Allen et al., 1980; Wetherington, 1979).

Experimental conditions were changed only when at least 15

sessions had occurred with no systematic trends in both

measures of attack, as determined by visual inspection of

daily plots and cumulative records.



Results and Discussion

All birds attacked at low levels during the first two

sessions during which no contingencies were programmed.

Zero levels of attack were observed for all birds during the

third session of this condition. Typical, positively

accelerated temporal patterns of keypecking were seen for

all birds during the FI component prior to the introduction

of the target birds. When the target birds were introduced,

each subject began to attack within the first session.

Topographical characteristics of attack were similar to

those reported in other studies (e.g. Dove, 1976), primarily

consisting of forceful pecking against the protective shield

and the exposed bib.








Representative cumulative records of responding are

presented in Figure 2 for P-7848, Figure 3 for P-5626, and

Figure 4 for P-1313. For P-7848 and P-1313, records are

shown from conditions when n was 1, 8, and 16; for P-5626

records shown are from conditions when n was 1 and 16.

There are two records for each bird from each condition. In

each set, keypecks stepped the response pen in the upper

record, and attacks stepped the response pen in the lower

record. These records illustrate several characteristics of

responding that occurred in all birds. First, keypecking

was generally characterized by a pause following

reinforcement, followed by a transition to a moderately high

rate. This transition was positively accelerated for P-

7848, but more abrupt for P-5626 and P-1313. Both

positively accelerated and "break and run" patterns of

responding have been maintained under FI schedules of food

presentation (e.g., Branch & Gollub, 1974; Ferster &

Skinner, 1957). Second, more attacks occurred when larger

amounts of food were delivered per interval. Third,

attacking usually occurred in bursts shortly after the last

food presentation of an interval (i.e., upon illumination of

the white keylight) and terminated abruptly sometime before

the onset of keypecking. None of the birds attacked in the

presence of the red keylight. Note that P-5626 occasionally

attacked well into the fixed-interval (indicated by arrows

in Figure 3). Although this was not a consistent within-








session characteristic of attack, it did occur inter-

mittently throughout the experiment with this subject.

While most theorists reject the notion that induced behavior

is an early response in a chain (Staddon, 1977), it is

possible that attacks occurring in later portions of the

interval were part of a heterogeneous chain that terminated

in keypecking. If such were the case, however, alternations

between attacking and keypecking might have been expected to

occur more frequently.

Figures 5, 6, and 7 relate the number of attacks per

interval with attack and the proportion of intervals

containing attack for P-7848, P-5626, and P-1313,

respectively, to the amount of food per interval, or n.

Values shown are means from the last 15 sessions of each

condition. For each subject, these measures of attack

generally increased monotonically as a function of n. These

functions can be characterized as increasing to a maximum at

some intermediate n value, and remaining at or near that

maximum with further increases. (Note that for P-1313 the

function for attacks per interval with attack increased with

each increase in n, up to 16 the last value examined with

this bird).

With subject P-7848, increasing n from 1 to 8 more than

doubled mean attacks per interval with attack and increased

the mean proportion of intervals with attack from 0.77 to

0.98. When n was changed from 8 to 16, mean attacks per








interval with attack again increased, from 132.5 to 176.2,

while the proportion of intervals with attack remained near

the maximum value. Both measures of attack were essentially

unchanged when n was increased to 24. Reexposure to various

n values produced the same general function, although both

measures were generally lower than those observed during the

initial exposures. This may have resulted from the

intervening exposure to larger food amounts or from a

general decrease in attack levels across sessions. Such a

decrease has been previously reported with induced attack

(Cherek & Pickens, 1970). It is likely, however, that the

former variable is responsible because no general decline in

attack was seen across sessions within any phase of the

experiment.

Both functions for P-5626 resembled those seen with P-

7848, except that attacks per interval with attack reached a

maximum at n = 8 (see Figure 6). Further increases in n

produced comparable levels of attacks per interval and the

same maximum proportion levels. The means of these measures

during the second (and third, for n = 1) exposure to various

n values were comparable, but slightly lower, to those

observed during initial exposures.

The data from the phases at lower n values under

conditions in which sessions were conducted every other day

(P-5626 and P-7848) and when sessions ended after 10

intervals (P-5626) suggest that the increases in attack were






37

indeed a function of increases in n, rather than a function

of some characteristic of the different conditions required

at larger n values. For example, it cannot be argued that

the higher levels of attack observed at large n values were

due simply to deprivation of the opportunity to attack that

resulted from conducting sessions every other day.

Although P-1313 had to be removed from the experiment

before being exposed to all conditions, the data for this

bird warrant examination. After attacking at relatively low

levels during the early sessions of the n = 1 condition,

this bird ceased attacking, and failed to do so for the

final 22 sessions under this phase. When n was increased to

eight, attacking occurred in the first session, and

persisted for the remainder of this phase. The mean levels

of attacks per interval with attack and proportion of

intervals with attack for the last 15 sessions were 43.6 and

0.97, respectively. When n was increased to 16, mean

attacks per interval with attack increased to 84.7 and the

proportion measure increased to 0.99 (see Figure 7). After

92 sessions under this condition, both keypecking and

attacking began to decrease until this subject failed to

engage in either activity. Probe sessions at other n values

failed to produce keypecking or attacking. This bird was

removed from the experiment and perished shortly thereafter.

The results presented in Figure 7 include only those







sessions prior to the sudden decrease and subsequent

cessation of keypecking and attacking.

The development of attack in P-1313 as a result of

changing n from one to eight is shown in Figure 8. This

figure shows daily levels of attack per interval with attack

for the last 15 sessions of the n = 1 condition and the

first 15 sessions of the n = 8 condition. This figure

reveals that the zero levels of attack observed when n

equaled one were substantially increased by the first

session when n was increased to eight. Attack continued to

occur at similar levels throughout this phase.

Note that for all birds, when conditions arranged for

intervals terminating in multiple grain cycle presenta-

tions--when n was greater than one--attack occurred in

nearly every interval (i.e., proportion values were usually

near 1.0). In contrast, when n was one, attack occurred in

fewer intervals per session. Thus, one major effect of

programming multiple grain cycle presentations was to

increase the likelihood of initiating attack, as well as to

increase the amount of attack per interval once it was

initiated.

A summary of keypecking data for each bird for all

conditions is provided in Table 2. For both P-5626 and P-

7848, response rates generally decreased and pause times

generally increased as a function of n. For P-1313, no







systematic trend can be seen over the range of parameter

values studied.

Decreases in operant response rates and increases in

pauses similar to those seen with P-7848 and P-5626 have

been reported on FI schedules as a function of feeder cycle

duration (Staddon, 1970), or milk concentration (Lowe,

Davey, & Harzem, 1974). These results have been attributed

to the "inhibitory" effects of food presentation (Lowe et

al., 1974). Other studies, however, have reported a

positive relation between operant response rates and

reinforcement magnitude, and are generally attributed to the

"motivational" or "strengthening" effects of food

reinforcement (see Bonem & Crossman, 1988, for a review).

The effects of reinforcement magnitude are quite

inconsistent across studies and appear to depend upon a

number of procedural characteristics. A more detailed

discussion of the effects of this variable on operant

behavior and the relevance to the present experiments will

appear in the General Discussion.

In summary, Experiment 1 revealed two major effects of

increasing the amount of food per interval on schedule-

induced attack: a) the amount of attack (as measured by

attacks per interval with attack) is a direct function of

the amount of food per interval, with this measure

increasing to a maximum at some n value and remaining at

high levels with further increases in n, and b) the






40

probability of initiating attack is higher when conditions

arrange for the delivery of multiple grain cycles rather

than a single cycle. These data extend those reporting that

the larger of two amounts of food induced more attack on FT

schedules (Flory, et al., 1988) by providing a

characterization of the function over a greater range of

parameter values.






























Figure 1. Diagram of experimental apparatus used to
secure the target pigeon and measure attacks. This
diagram is copied from Azrin, Hutchinson, & Hake
(1966).








42

































too

14spa"l
way














Pw/I
Af"








h bjstCuOSw 3"tc..
lo '"Siol
PooIU

























Figure 2. Sample cumulative records from portions of
sessions from n = 1, n = 8, and n = 16 conditions for
P-7848 during Experiment 1. In the upper record of each
condition, each keypeck stepped the response pen, the
response pen deflected with each food presentation and
reset after the last food presentation of an interval,
and each attack deflected the event pen. In the lower
record of each condition, each attack stepped the
response pen, the response pen reset after the last
food presentation of an interval, and each food
presentation deflected the event pen. Records are
taken from sessions in which the attacks per interval
with attack measure closely approximated the mean for
the last 15 sessions.































n1 6









3Q M3 N -MIN


7=



i~L/L/
..

i-































Figure 3. Sample cumulative records from entire
sessions n = 1 and n = 16 conditions for P-5626 during
Experiment 1. All conventions are as in Figure 2.













P-5626

n==




n16

I3


o n -1 6












3O-;0MIN------































Figure 4. Sample cumulative records from n = 1, n = 8,
and n = 16 conditions for P-1313 during Experiment 1.
All conventions are as in Figure 2.










n=8


--- 30 MIN I


-,jjjjj---,u




























Figure 5. Attacks per interval with attack and the
proportion of intervals with attack as a function of
the amount of food per interval (n) for P-7848 from
Experiment 1. Closed circles are from the initial
exposure to each n value, open circles are from the
second exposure to n = 1 and n = 16 conditions, and
open triangles are from the third exposure to the n = 1
condition. See text for specific characteristics of
each condition. Values are means taken from the last
15 sessions. Vertical bars indicate ranges.









Determination
0-- 1st
0 2nd
A 3rd


AMOUNT OF FOOD (n)


P-7848


240-

200-

160-

120

80

40


1.000-



0.750-



0.500-



0.250-



0.000-


1 1






























Figure 6. Attacks per interval with attack and the
proportion of intervals with attack as a function of
the amount of food per interval (n) for P-5626 from
Experiment 1. All conventions are as in Figure 5.







P-5626


Determination
-- 1 st
0 2nd
A 3rd


AMOUNT OF FOOD (n)


100.
1 O


80.
O-
60-


40-


20-


0


1.0001 --



0.750-



0.500



0.250



0.000 ,






























Figure 7. Attacks per interval with attack and the
proportion of intervals with attack as a function of
the amount of food per interval (n) for P-1313 during
Experiment 1. All conventions are as in Figure 5.







P-1313


*


AMOUNT OF FOOD (n)


160-


120-


80-


40-


1.000-


0.750-


0.500-


0.250-


0.000




















4) 0

wO


U

cvco
~4 4

'4.4




Uo


.1I
4 10





044
en





wcn





--4 4-)

44 V
tot










4J W~
4Jvr












4.) E
H LO








-II






-rI4-4 I
(1)rln






4-)






0
ci)J






0
>U2d




4J 4-)

P-4 0
>4



to





to -H
W pe





LX



--I (t M
fZ4 r-I 44I














0
*--^0

S-..o
Se


*^=====^-0


I I
00o
( d~-


- z

- 0






)o

r"-
I


>3OVIIV HIIM \IVAd3INI d3d S>,iOV1V

















TABLE 1

The order of conditions and number of sessions in each for
all subjects in Experiment 1. Each subject responded on a
Ch FI t FR 1 x n schedule of food presentation. Sessions
ended after 15 intervals and run 5 days per week unless
otherwise noted.


P-7848
t = 12 min


n value


sessions


120
61
32
27
32
52
34


P-5626
t = 4 min








P-1313
t = 4 min


1
8
162
241,2
1
161
11,2


138
83
78
44
120
47
51


117
58
98


Sessions conducted every other day
2Sessions ended after 10 intervals















TABLE 2

Overall keypeck rates and average pause times during the FI
for each subject for every condition of Experiment 1.
Values are means for the last 15 sessions. Values in
parentheses are ranges. Each subject responded on a Ch FI t
FR 1 x n schedule.


keypecks/min


pause/interval(min)


P-7848
t = 12min


(20.1-29.9)
(20.5-33.5)
(15.3-25.1)
(11.3-17.2)
(25.0-41.7)
(24.2-30.5)


(21.7-30.8)
(17.5-45.0)
(18.3-32.8)
(10.6-23.9)
(23.1-37.8)
(6.5-24.5)
(21.9-33.3)
(22.4-37.8)



(0.5-56.9)
(23.8-46.5)
(9.9-40.8)


2.9
3.2
4.3
4.5
2.9
3.0


1.5
1.7
2.0
2.2
1.5
2.1
1.5
1.8



2.3
2.1
1.9


(1.7-4.0)
(1.7-4.3)
(3.2-5.5)
(3.5-6.1)
(1.6-4.0)
(1.6-5.2)




(1.3-2.1)
(1.3-2.4)
(1.1-2.5)
(2.0-3.0)
(0.9-1.9)
(1.6-2.6)
(1.2-2.1)
(1.4-2.3)



(1.1-8.7)
(1.5-2.7)
(0.9-2.6)


24.5
24.0
18.0
14.2
30.8
27.8


P-5626
t = 4min


27.4
25.6
20.8
17.4
27.7
19.7
30.1
29.0


P-1313
t = 4min


32.6
37.3
25.2












EXPERIMENT 2


Introduction


The results from Experiment 1 indicated that induced

attack was a monotonic, increasing function of the amount of

food presented dependent upon keypecking. Data from studies

of induced polydipsia with rats, however, suggest that

relations obtained from manipulations of amount of food

across sessions may change when comparisons of different

food amounts are made within sessions. When presented food

pellets according to an FT schedule, rats drank slightly

more when multiple pellets (four or six) were delivered than

when one pellet was delivered each interval per session

(Reid & Dale, 1983; Reid & Staddon, 1982). However, when

intervals ending in multiple pellets were interspersed with

intervals ending in one pellet within experimental sessions,

rats drank more in those intervals that followed one pellet

and during those intervals that ended in one pellet, if

those intervals were signalled (Reid & Dale, 1983; Reid &

Staddon, 1982). While the determinants of the differences

in across- and within-session comparisons are not clear,

these data suggest that the function relating induced






60

polydipsia to amount of food may depend critically upon the

context in which the amount of food is manipulated.

Experiment 2 was conducted to determine if the

relationship revealed in Experiment 1, when the amount of

food was varied across experimental phases, would hold when

varied within sessions. If a comparable relation is

obtained, then the generality of the results of the first

experiment would be demonstrated. However, if differences

similar to those discussed above with polydipsia are seen,

further analysis would be required to determine the factors

responsible.



Method

Subjects

P-5626 and P-7848 served as experimental subjects.

Each was maintained at 80% of its free-feeding body weight.

Each subject was paired with a target pigeon. For P-5626,

the target was the same as in Experiment 1; for P-7848, the

target was different than in Experiment 1. The target for

P-5626 became ill midway through this experiment and was

replaced. Each target was given free access to food and all

birds were individually housed with water and health grit

continuously available.








Apparatus

The apparatus used in this experiment was the same as

in Experiment 1.

Procedure

After completion of the sequence of conditions listed

in Table 1, P-5626 and P-7848 were exposed to a two-

component multiple schedule in which n = 1 and n = 16

conditions alternated irregularly within experimental

sessions. For P-5626 the schedule was a Mult [Ch FI 4 FR 1

x 1] [Ch FI 4 FR 1 x 16]; the schedule for P-7848 was a Mult

[Ch FI 12 FR 1 x 1] [Ch FI 12 FR 1 x 16]. The component

that began the session was determined randomly. Components

alternated irregularly and lasted either 2, 3, or 4

intervals. For P-5626, a clicking sound accompanied the n =

16 component. For P-7848 the clicker accompanied the n = 1

component. Sessions were terminated after 9 intervals had

occurred in each component. Components were separated by

30-s time-outs (TOs) during which the chamber was dark, no

experimental events were programmed, and attacks were

recorded (but had no effect on TO duration). Changeover

contingencies in Experiment 2 were identical to those in

Experiment 1.

After 51 sessions for P-5626 and 47 sessions for P-

7848, the TOs were lengthened to 60-s. This condition

lasted 33 sessions for P-5626 and 30 sessions for P-7848.








The target for P-5626 was replaced on the ninth session of

this condition.




Results and Discussion

Figures 9 and 10 show representative cumulative records

of responding under the multiple schedule for P-5626 and P-

7848, respectively. Several general characteristics of

responding are illustrated in these records. First, keypeck

patterns for both birds resembled those seen in Experiment

1. Second, attacks usually occurred during the periods

immediately after the last grain presentation of an

interval. (Note that P-7848 often continued to attack well

into the interval). Third, more attack was induced in the n

= 16 component.

The third characteristic listed above is quantitatively

summarized in Figures 11 and 12. Figure 11 presents attacks

per interval with attack and proportion of intervals with

attack in each component for P-5626; Figure 12 shows these

data for P-7848. For P-5626, both measures of attack were

higher during the n = 16 component, but the differences in

attack were not as great as seen in Experiment 1. In

Experiment 1, this bird attacked in virtually every interval

when n was 16, while during the multiple schedule, attack

usually occurred in all but one interval. This interval was









usually the first interval after a component change or the

first interval of the session.

The data for P-7848 were similar to those for P-5626 in

that, although more attack was observed under the n = 16

condition than when n was 1, the differences were not as

great as in Experiment 1. This was primarily the result of

elevated levels of attack (in both measures) under the n = 1

condition. Attacks per interval under the n = 16 condition

were similar in both Experiments. As with P-5626, this bird

did not attack in every interval when n was 16, and

intervals that lacked attack in this component were usually

the first interval following a component change or the first

interval of the session.

Keypecking data from Experiment 2 are shown in Table 3.

As in Experiment 1, rates were lower and pause times were

longer when n was 16.

One advantage of employing a multiple schedule for the

present comparison is that, because both experimental

conditions (n = 1 and n = 16) occur within the same session,

attacks during both conditions are similarly exposed to

effects of extraneous, uncontrolled variables. Although not

necessarily the case, it is quite possible that those

variables do not operate differentially on attack in the two

components of the multiple schedule. If this is indeed the

case, then it might be illustrative to compare the number of

sessions in which attack was higher under the n = 1 and n =








16 conditions. For both birds, attacks per interval with

attack were higher during the n = 16 component in each of

the last 15 sessions. For the proportion measure, attack

was higher during the n = 16 component in 6 of these

sessions for P-5626 and in 5 of these sessions for P-7848.

This measure was never higher during the n = 1 component for

P-5626 and was higher in only 1 session for P-7848.

Employing a multiple schedule to compare conditions

within experimental sessions is not without its

disadvantages. Interactions between components is

frequently observed in studies using multiple schedules

(e.g. Bloomfield, 1966; Pear & Wilkie, 1971; Reynolds,

1961). It is possible that such interactions occurred in

the present experiment. Inspection of the cumulative

records in Figures 9 and 10 reveals that for both birds

elevated levels of attack were sometimes seen in the first

interval of n = 1 components and reduced levels were

sometimes seen in the first interval of n = 16 components.

It is quite possible that attacking in the first interval of

a component is at least partially controlled by the amount

of food delivered in the final interval of the preceding

component rather than by the stimulus correlated with the

current component, despite the 30-s TO's between components.

When the TO durations were increased to 60-s, no change in

this characteristic of attack, or in overall levels of

attack was observed. The smaller differences in levels of








attack between n = 1 and n = 16 conditions in Experiment 2

(compared with those seen in Experiment 1), also may have

resulted from interaction between the two components.

Perhaps attacking was partially controlled by some overall

session average of food amount, and this source of control

attenuated the differences seen in Experiment 1. Despite

these limitations, the data presented in Figures 9, 10, 11,

and 12 and the proportion of sessions in which attack during

the n = 16 component was greater provide substantial

evidence that attack is more likely when larger amounts of

food are delivered, even when large and small amounts

alternate within experimental sessions.




















'-I






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4J

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04




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1 0






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krz








08()
ca













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uw
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*-I 0




ticU
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-r-

>aa
t 3 r
.f-I
44


















































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r-4







C-4
41





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I4 0



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0)











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tz


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69






I

^ ^
^ ^^































Figure 11. Mean levels of attacks per interval with
attack and proportion of intervals with attack for P-
5626 for n = 1 and n = 16 components during Experiment
2. Striped bars are from the n = 16 components.
Values are from the last 15 sessions. Vertical bars
indicate ranges.







P-5626


80-
s-

60-


40-


20-


0


SI


1 16
AMOUNT OF FOOD (n)


1 I I .L_


1.000



0.750



0.500



0.250



0.000































Figure 12. Mean levels of attacks per interval with
attack and proportion of intervals with attack for P-
7848 for n = 1 and n = 16 components during Experiment
2. All conventions are as in Figure 11.







P-7848


1 16
AMOUNT OF FOOD (n)


200

160

120

80

40

0


1.000


0.750


0.500


0.250


0.000












TABLE 3

Overall keypeck rates and average pause times for both
subjects during the FI in each component of the mult [ch FI
t FR 1 x 1] [ch FI t FR 1 x 16] schedule of food presentation
used in Experiment 2. Data are from conditions when the time-
out duration was 30 s. Values shown are means for the last
15 sessions. Ranges are indicated in parentheses.


P-5626
t = 4 min


keypecks/min


22.0 (19.4-26.1)
14.7 (10.0-22.2)


P-7848
t = 12 min


24.7 (17.2-33.6)
18.0 (9.5-24.8)


pause(min)

1.1 (0.7-1.6)
1.9 (1.4-2.7)




1.7 (1.0-2.6)
3.2 (1.9-5.0)














GENERAL DISCUSSION


In both experiments, induced attack by pigeons was

positively related to the amount of food delivered on an FI

schedule. In Experiment 1, when the amount of food per

interval was examined across phases, attacking increased to

a maximum and remained at high levels with further increases

in food amount. In Experiment 2, when two different amounts

alternated within the context of a multiple schedule, attack

was higher in the component that programmed more food, with

the differences slightly less than those observed in

Experiment 1.

Considerations of the results of the present study can

conveniently be made within the context of the theoretical

frameworks presented in the General Introduction. The

frameworks discussed were the classification of induced

attack as a member of a class of "adjunctive behaviors"

(Falk, 1969, 1971), the view of induced attack as arising

from aversive properties of intermittent schedules of food

presentation (Azrin, 1961; Azrin et al., 1966; Hutchinson et

al., 1968), an analysis of induced attack as a form of

"interim activities" (Staddon, 1977; Staddon & Simmelhag,

1971), and the view that induced attack results from






76

"arousal" generated by presentation of food (Killeen, 1975;

Killeen et al., 1978). In addition, two other

interpretations of the present results will be considered,

one in terms of principles of reflexive behavior, and

another in terms of "an opponent-process theory of

motivation" (Solomon & Corbit, 1974).

The results of the present experiments are, for the

most part, incompatible with Falk's view. Although attack

observed in these studies shares a number of characteristics

with other induced activities classified as adjunctive

(e.g., attack was induced by intermittent food presentation,

and occurred in the post-reinforcement period), a

monotonically increasing function relating attack to amount

of food is not predicted from Falk's consummatoryy rate

hypothesis." Recall that in Falk's view, adjunctive

activities are bitonically related to the rate of food

presentation, with high levels induced at intermediate food

rates, and low levels induced both at high and at low food

rates (Falk, 1969, 1971). Thus, according to this view,

levels of attack in Experiment 1 should have decreased

substantially at the larger food amounts (n = 16 and n =

24). While it might be argued that such a decrease would

have occurred had larger amounts of food been examined,

previous experiments on induced drinking and induced attack

have shown that, when fixed food amounts were intermittently

presented (e.g., one food pellet or one grain cycle), levels








of these behaviors began to decline as food rates were

increased to greater than one unit per 2.5 min (0.4 units

per min) (Falk, 1966). Other data indicate that induced

behaviors begin to decline as food rates are increased to

greater than one unit per minute (e.g., DeWeese et al.,

1972; Falk, 1966; Flory, 1969). These results suggest that

the highest food rates in Experiment 1 were sufficient to

produce a decrease predicted by Falk's hypothesis. During

the present experiment, attack levels continued at maximum

levels at food rates of six units per minute (P-5626 at n =

24) and of two units per minute (P-7848 at n = 24). Also,

as mentioned earlier, other studies examining induced attack

(Flory et al., 1988) and induced drinking (Bond, 1973) under

different combinations of food amounts and interfood

intervals have reported data at odds with the consummatory

rate hypothesis. Those results, as well as those reported

here, suggest that it may be useful to consider

manipulations of food amount and interfood interval as

separate variables.

The data from the present study at first seem

incompatible with the view that induced attack is produced

by aversive properties of intermittent schedules of food

presentation. If aversive aspects of conditions arranged in

the present experiments were responsible for the production

of attack, it seems likely that smaller amounts of food

would have resulted in more attack. In the sense that








conditions arranging for lower frequencies or amounts of

reinforcement are less preferred (see de Villiers, 1977),

they could be considered as relatively more aversive, and

might be expected to induce higher levels of attack. Such

is certainly the case when the extremes are programmed, as

when periods of FR 1 alternate with periods of extinction

(Azrin et al., 1966).

An interpretation of the present results in terms of

schedule aversiveness is2 still possible, however, by

considering FI schedules as suggested by Schneider (1968).

In this view, FI schedules are similar to programming

alternating periods of extinction and periods in which a VI

schedule is in effect (with the value of a given interval

determined by the post-reinforcement pause). Thus, the

period just after food presentation functions as an SA, and

the period towards the end of the interval functions as an

S. Indeed, with respect to induced behavior, it has been

suggested that the periods of zero reinforcement probability

just after food presentation on intermittent schedules

function similarly to programmed periods of extinction

(e.g., Azrin, 1961; Hutchinson et al, 1968; Richards &



2The term aversiveness is used here only as a reference to
certain effects upon behavior. A set of conditions is
called aversive only to the extent that these conditions are
escaped and avoided, or to the extent that aggressive
behavior is produced. Use of the term is not meant to imply
that the property of aversiveness exists independent of any
measurable dimension of behavior, and is measured, if at
all, in some separate dimension.








Rilling, 1972). In viewing FI schedules of food

presentation in this fashion, the increase in attack as a

function of increasing the amount of food may have resulted

from an increase in the relative aversiveness of post-food

stimuli. Such an effect might be expected on the basis of

data showing negative behavioral contrast in multiple

schedules. That is, when the rate of food presentation is

increased in one component of a multiple schedule, the rate

of responding in the other (unchanged) component often

decreases (e.g., Reynolds, 1961). Thus, the "strength" of

operant behavior maintained in a given set of stimulus

conditions is dependent upon context. It is possible that

the aversive characteristics of SA periods are also

dependent upon context. Indeed, the aversiveness of the

post-reinforcement period during ratio schedules (as

indicated by the likelihood of escape) is dependent upon the

size of the ratio (e.g., Appel, 1963; Azrin, 1961; Thompson,

1964). Thus, the aversiveness of the early portions of the

FI in the present experiment may have increased as a result

of increases in the amount of food presented in the terminal

component, resulting more attack and less keypecking. Such

an interpretation is supported by data demonstrating higher

levels of attack during extinction components of a multiple

schedule as a function of the number of food reinforcements

delivered according to an FR 1 schedule in the other

component (Azrin et al., 1966).








An important test of the behavioral contrast view

presented above might be to compare the effects of

reinforcement amount on schedule-induced escape. This view

predicts that larger amounts of reinforcement would induce

more escape. Also, it might be informative to evaluate the

effects of a type of "errorless" discrimination training

(Terrace, 1963,1964). In errorless discrimination training,

S' is gradually introduced so that its behavioral function

is acquired with very few "errors" (i.e., responses during

S6). Terrace (1963, 1964) reported that the usual

"emotional" responses (e.g., aggression) often observed

during S' periods were lower in experimental subjects

trained errorlessly. Terrace also reported that

manipulations usually resulting in behavioral contrast

failed to do so in subjects trained in this fashion. If

the effects of the amount of food reinforcement on attack in

the present experiments are an example of behavioral

contrast, then subjects with a training history in which the

FI schedule parameter was increased very gradually (i.e., a

gradual introduction of SA) might be expected to attack less

than subjects for which the FI schedule parameter was

abruptly increased.

The relationship of the present data to the theoretical

position offered by Staddon and his colleagues (Staddon,

1977; Staddon & Ayers, 1975; Staddon & Simmelhag, 1971) is

not straightforward. Recall that, in this framework,








because motivational variables governing interim responses

depend upon those governing terminal responses, operations

that increase the reinforcing efficacy of the terminal event

should produce increases in levels of both interim and

terminal activities. Indeed, the principal findings of the

present studies provide support for Staddon's

conceptualization. The monotonic increasing function

relating induced attack to food amount is consistent with

predictions based upon this view. However, rather than

increasing as predicted, terminal responding (keypecking)

decreased as a function of food amount. Thus, while it

seems that this view is useful with respect to predictions

of the effects of food amount on schedule-induced attack,

keypeck data from the present studies make it difficult to

assess the utility of this view as a general conception of

behavior.

Recent studies seem to have occasioned a slight

restructuring of Staddon's view (Reid & Dale, 1983; Reid &

Staddon, 1982). In these studies, induced drinking (an

interim activity) and "head-in-feeder" (a terminal activity)

in rats were examined during FT 60-s schedules of food

presentation. In the experiment by Reid & Staddon (1982),

occasional intervals ending in six pellets were interspersed

with intervals that usually ended in one pellet. In the

Reid & Dale (1983) study, intervals ending in four pellets

randomly alternated with intervals ending in one pellet. In









both of these experiments, levels of interim drinking were

lower and levels of terminal responding were higher during

intervals that followed presentation of the larger food

amount. When different stimuli were present during

intervals ending in different food amounts, levels of

drinking were lower and levels of terminal responding were

higher in intervals beginning and ending in the larger food

amount. These results led the investigators to suggest that

terminal activities are both elicited by food and occur in

"anticipation" of food, and that terminal activities and

interim activities are "reciprocally, linearly related"

(Reid & Dale, 1983). In this view, then, interim activities

are only indirectly controlled by food presentation, and the

amount of interim responding observed under intermittent

schedules is primarily determined by the amount of terminal

responding generated by that schedule. The results of the

present experiments suggest that induced attack and operant

behavior are reciprocally related: as attack increased,

keypecking decreased. However, the functions relating each

of these responses to food amount are directly opposite of

those predicted on the basis of data reported by Reid & Dale

(1983) and Reid & Staddon (1982).

The data from studies by Reid & Dale (1983) and Reid &

Staddon (1982) discussed above were obtained when

manipulations of food amount made within experimental

sessions. However, as noted in the Introduction to









Experiment 2, the effects of food amount in those studies

were entirely different from comparisons that were made

across sessions (Reid & Staddon, 1982), or across phases

(Reid & Dale, 1983). In those cases, the larger of two food

amounts induced more drinking, but had no systematic effect

on terminal responding. In contrast, in the present

studies, induced attack was positively related and

keypecking was inversely related to food amount, both when

comparisons were made within sessions and across phases.

The reasons for the disparity in these findings are not

clear. Perhaps some of the differences in results were due

to differences in species used, responses measured, inducing

schedules, apparatus used, or measures of induced

responding. In the studies by Reid & Staddon (1982) and

Reid & Dale (1983), the mean percent of 1-s bins containing

drinking and head-in-feeder were measured as a function of

time in the interfood interval. This measure provided an

estimate of the probability of these two activities at

various points within the interfood interval. It is

possible that such partial-interval recording resulted in

different estimates of responding than if more conventional

measures had been used (e.g, rate, response per interval,

total amount). This seems unlikely, however, given that the

correspondence between interval recording methods and

continuous measures (such as response rate) is greatest when

short intervals are used (Powell, Martindale, & Kulp, 1975),








and that rather short intervals were used in those

experiments (l-s). Thus, it seems as though the differences

in data obtained in those experiments and in the experiments

presented here result from features other than measurement

procedures.

The present results also relate to the theoretical

framework proposed by Killeen (1975) and Killeen et al.,

(1978). This conceptualization suggests that a variety of

induced behaviors result from "arousal" generated by food

presentation. Repeated presentation of food produces an

accumulation of arousal such that the excessive character of

induced behavior is observed. This model predicts that

larger amounts of reinforcement ("incentive") should produce

more arousal, and thus, more induced behavior (Killeen et

al, 1978). The direct relation between induced attack and

amount of food presented here are in accord with this view.

Killeen et al., (1978), however, go on to suggest that as

food amount is increased, it is possible that arousal will

be diminished through satiation. Thus, at very large food

amounts, induced attack, for example, might be expected to

decrease. Such a decrease was not seen in the present

results. Satiation, however, did not appear to be a factor

in the present experiment. Inspection of the cumulative

records presented in Figures 2, 3, and 4 reveals little

evidence of a decline in keypecking as session progressed

for any subject during any phase of Experiment 1.








While the increase in attack as a function of food

amount is predicted by Killeen's model, other features of

the present results differ from predictions based upon this

model. For example, Killeen et al., (1978) reported peak

rates of activity at about one-quarter into the interfood

interval, regardless of interval duration. In the present

study, highest attack rates were observed during the period

immediately following food presentation. Indeed, inspection

of cumulative record figures reveal that, for the most part,

attacking occurred at rather constant rates in the early

portion of the interval (rather than positively accelerated

rates, as predicted by Killeen). Note, that there were

occasional exceptions to both of these general

characteristics (see Figures 3 and 10). However, these were

not consistent across conditions or across birds. Thus, the

differences in temporal characteristics between attack seen

here and activity measured by Killeen et al. (1978), suggest

that these behaviors may result from different processes.

A alternative interpretation of the present results is

derived from relations obtained from studies of reflexes.

Although attack occurs closely following food presentation,

as might be expected if it was elicited, some investigators

reject the possibility that attack and other induced

activities are respondent in nature (e.g., Falk, 1971).

Certain characteristics are often cited that seem to

preclude classification of induced activities as








unconditional respondents elicited by food or by eating.

For example, induced behaviors usually take several sessions

to develop (e.g., Falk, 1971; Magyar & Malagodi, 1981), they

can be modified by consequences (Bond, Blackman, & Scruton,

1973; Dunham, 1971), and certain operations will produce a

shift in their temporal locus within the interfood interval

(Gilbert, 1974). However, it has been argued that the

tendency to reject interpretations of induced behavior as

respondent is premature (Wetherington, 1982). Wetherington

reviews data from studies on the effects of repeated

elicitations, such as sensitization, habituation, temporal

conditioning, temporal summation, and emergence of new

unconditional responses. These data suggest that many

respondents may actually possess characteristics that have

been cited as evidence against a view that schedule-induced

behavior is elicited. The results from the present

experiments are in accord with predictions that are likely

to emerge from a view of induced attack as an unconditional

response to food presentation. Increases in attack as a

function of increases in the amount of food can be

considered an example of the Law of Intensity/Magnitude

(Sherrington, 1906).

A final interpretation of the function relating attack

to food amount can be made on the basis of an "opponent-

process theory of motivation" (Solomon & Corbit, 1974).

These theorists argue that presentation of an emotion-








arousing stimulus (e.g., food or electric shock) produces

two important effects. The initial effect is called the

"primary affective reaction," or "a process," and is what

is generally expected in the presence of that stimulus

(e.g.,"happiness" if it is a positive reinforcer). The a

process is assumed to elicit, in turn, an "affective after-

reaction," called the "opponent" or "b process," that

generates an opposite emotional reaction (e.g.,

"unhappiness"). The overall emotional change that occurs

when a stimulus is presented and then withdrawn is the net

result of the primary and opponent processes. The a process

ceases immediately when the stimulus is withdrawn, while the

b process lingers unopposed after the stimulus is

terminated. This model can be described as homeostatic in

that it is assumed that physiological mechanisms underlie

these processes and act to control emotional behavior by

minimizing deviations from emotional neutrality.

The following example may help to clarify the nature of

the opponent processes. Solomon & Corbit (1974) describe

behavior changes in a dog subjected to "intense" aversive

stimulation (electric shock). The dog was placed in a

Pavlov harness and was given periodic 4-mA, 10-s electric

shocks. The initial effect of shock presentation was

described as "terror and panic," which included expulsive

defecation and urination, pupil dilation, piloerection, and

heart rate increase. After shock was terminated, this "a








state" gave way to a state of "stealth," during which the

animal was subdued and relatively inactive, and during which

heart rate decreased to levels below those observed prior to

shock delivery. After a minute or so, this "b state" was

replaced by normal behavior patterns and heart rate. After

a number of repeated presentations of shock, the

characteristics of the a state were diminished (e.g.,

behavior patterns were described as "annoyed and anxious,"

and heart rate increase was attenuated), and b state

characteristics were augmented (e.g., behavior patterns were

described as "euphoric and active," and heart rate decreases

were greater) compared to those seen during initial shock

presentations. In this framework, the a process is

unchanged, and the b process is strengthened, by repeated

stimulus presentation. This presumably explains the changes

observed in the dog's behavioral patterns and heart rate in

the above example. Solomon & Corbit (1974), interpret a

number of behavior phenomena in terms of this theory, such

as drug addition and certain characteristics of escape and

avoidance.

The opponent-process theory of motivation seems

relevant to schedule-induced behavior, particularly induced

attack. Schedule-induced attack generally occurs at high

probability just after food presentation (i.e., during the

period in which the effects of the b process are strongest).

In addition, according to Solomon & Corbit, (1974),








activities generally observed during aversive conditions

should occur during post-food periods. Attack is often

observed under conditions in which aversive stimuli are

presented (Azrin et al., 1965; Azrin et al., 1964: Ulrich &

Azrin, 1962). Also, several food presentations are often

required before attack and other schedule-induced activities

develop (Dove, Rashotte, & Katz, 1974; Magyar & Malagodi,

1980). This characteristic of induced behavior is predicted

by the opponent-process theory, due to strengthening of the

b process by repeated stimulus presentations. Finally, the

opponent-process theory suggests that increases in the

intensity of the stimulus (e.g., food amount) should result

in an increase in both the a process and the b process. In

example above in which a dog was presented periodic 10-s

electric shock, when shock intensity was increased from 4-mA

to 8-mA, a moderate increase in the magnitude of the heart

rate elevation was observed during shock, and a dramatic

increase in the magnitude of the heart rate decline was

observed following termination of shock (Church, LoLordo,

Overmier, Solomon, & Turner, 1966). These data are

compatible with the relation between food amount and attack

observed in the present study: as the amount of food was

increased, the magnitude of the b process is increased,

resulting in more attack.

Finally, the effects of food amount on keypecking in

the present experiment must be considered. A number of









studies have indicated that the function relating operant

responding to reinforcement magnitude is positive,

especially when VI schedules are concurrently or multiply

arranged (Catania, 1963; Fantino, Squires, Delbruck, &

Peterson, 1972; Merigan, Miller, & Gollub, 1975). This

relation has also been observed under simple FI schedules

(Guttman, 1953), and under FI second-order schedules of

token reinforcement (Malagodi, Webbe, & Waddell, 1975). The

data reported here and elsewhere, however, seem to suggest

that the relation between reinforcement magnitude and

operant responding is negative. For example, when five

different feeder cycle durations (Staddon, 1970), and when

four different milk concentrations (Lowe et al., 1974) were

randomly presented on FI schedules, operant response rates

decreased and pause times increased as a function of the

preceding reinforcement magnitude. Indeed, there is

considerable disagreement about the effects of reinforcement

magnitude on operant behavior. The effects of this variable

depend critically upon the procedures used, and upon the

baseline schedules under which reinforcement is presented.

For a review of the literature in this area, and a

discussion of methodological and theoretical issues relevant

to these studies, see Bonem & Crossman, (1988).

Presentation of reinforcing stimuli often have multiple

behavioral effects. In addition to rate increasing, or

strengthening effects, reinforcement can also have






91

discriminative properties (e.g., Zimmerman, 1971). Perhaps

inconsistencies in the effects of reinforcement magnitude on

operant behavior result, in part, from differences in the

degree to which certain schedules establish reinforcement

presentation as discriminative. For example, post-

reinforcement pauses typical of behavior maintained by FR

and FI schedules of have been interpreted as resulting from

SA properties of reinforcement presentation, in that

reinforcement never closely follows a previous reinforcement

(e.g., Ferster & Skinner, 1957). It is quite possible that

the increases in pause duration as a function of

reinforcement magnitude observed in the present study, and

in other studies (Lowe, et al., 1974, Staddon, 1970), result

from an increase the SA function of reinforcement delivery.

The increase in attack observed in the present experiments

is also consistent with this interpretation. Thus, under

conditions in which reinforcement presentation is less

likely to serve an S6 function (e.g., VR and VI schedules),

increasing reinforcement magnitude might not produce an

increase in pausing and induced attacking.

It is also possible that the increase in pausing by P-

7848 and P-5626 was an indirect function of the increase in

attacking. That is, keypecking began later in the interfood

interval under larger food amounts simply because attacking

continued later into the interval. This did not appear to

be the case as causal observation and inspection of the






92

cumulative records (Figures 2, 3, 9, and 10) indicated that,

in most cases, post-reinforcement pauses were not entirely

subsumed by attacking, even at large food amounts. Precise

statements regarding the interaction of keypecking and

attacking, however, require more extensive data analysis

than possible here.

In conclusion, the data presented in these experiments

are important for a number of reasons. For example, while

relevant to each of the theoretical positions discussed

above, the relationship between attack and food amount

observed here does not provide conclusive evidence for the

selection of one position over the others. Indeed, in view

of the literature on schedule-induced behavior as a whole,

such a selection is extremely difficult. Each of these

theoretical frameworks is supported by data from some

studies but not others. It is contended here that a number

of schedule and consequence variables have not been studied

extensively enough to permit adequate theoretical

integration (See General Introduction). Thus, the results

of the present experiments are important in that a

functional relation between attack and food amount is

demonstrated over a range of parameter values not previously

reported, and the generality of that relation is extended by

showing comparable effects during a multiple schedule. Only

after further analyses of this sort, can questions

pertaining to the utility of these, or other, theoretical







93

views be answered. In addition, the data presented here are

relevant to issues regarding classification of various

schedule-induced activities. It appears that induced attack

and induced polydipsia are not always related to amount of

food reinforcement in the same way. Although many of the

theoretical positions presented above tend to classify

induced activities together, the data from the present

experiments suggest that these activities may result from

different properties of intermittent reinforcement schedules

and, thus, may be more profitably considered as functionally

distinct.












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