SCHEDULE-INDUCED DEFECATION FREDERICK RAYFIELD

JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

SCHEDULE-INDUCED DEFECA TION

FREDERICK RAYFIELD, MARVIN SEGAL, AND ISRAEL GOLDIAMOND

THE UNIVERSITY OF CHICAGO

Excessive defecation, typically considered to be a concomitant of stress, was experimentallyinduced or eliminated under specific schedules of positive reinforcement of lever pressingby rats. The schedules were, by and large, those under which polydipsia is typically induced.In the first of three experiments, rats under fixed-interval 32-second schedules and variableinterval 32-second schedules for food and water reinforcers defecated profusely, but notunder fixed-interval one-second schedules or other small interval schedules. Somewhathigher rates of defecation were observed on variable interval 32-second schedules than onfixed-interval 32-second schedules. In a second experiment, fixed-ratio schedules were used,some of which resulted in responding such that reinforcement densities were similar to thoseon the interval schedules that induced defecation. Defecation was not systematically inducedby these ratio schedules. In a third experiment, fixed-time schedules of food presentationswere utilized. High rates of defecation were induced comparable to those induced by in-terval schedules of the same time parameter. No other behavior commonly termed "emo-tional" was observed in any of these experiments.Key words: defecation, schedule-induced behavior, fixed interval, variable interval, fixed

time, fixed ratio, emotionality, conditioned suppression, rats

In investigations of operant behavior, ancil-lary activities may be observed that are notspecifically reinforced by the experimental pre-sentation of stimuli such as food or water.Where these ancillary activities vary systemati-cally with manipulations of the reinforcementschedule that governs an experimentally de-fined operant, so that they may thereby be pro-duced or eliminated, these activities may bereferred to as "adjunctive" or "schedule-in-duced" behavior, as distinguished from "sched-ule-governed" behavior, which describes theoperant involved. Among such schedule-in-duced behavior is the polydipsia first reportedby Falk (1961, 1964) in the pioneering researchthat brought to attention the field of schedule-

The research reported was supported in part by theResearch in Behavior Analysis account, the Division ofBiological Sciences of The University of Chicago andby State of Illinois DMHDD #924-21. Frederick Ray-field was supported in part by N.I.M.H. Training Grant#5T32-MH-256. The authors thank Paul Andronis forvaluable assistance conducting the third experimentand Lynn Andronis for excellent secretarial and figurework. Fredrick Rayfield's present address is Departmentof Psychology, Box 177, Roosevelt University, 430 SouthMichigan Avenue, Chicago, Illinois 60605; Drs. Segaland Goldiamond, Department of Psychiatry, The Uni-versity of Chicago, 950 East 59th Street, Chicago, Illinois60637.

induced or adjunctive behavior. In Falk's ex-periments, bar pressing by rats was typicallyreinforced by delivery of food under a VI 60-sec schedule. The robustness of the schedule-induced behavior was evident in the rats' con-sumption, through licking a dipper, of as muchwater as half their body weight during a ses-sion of 180 minutes. Such schedule-inducedpolydipsia has also been reported on fixed-in-terval reinforcement of lever pressing and dur-ing free presentations of food at regular inter-vals (FT schedules). Temporal schedules havebeen reported as inducing other similar typesof behavior, such as air licking (Mendelson,Zec, & Chillag, 1971) and alcohol consumption(Falk, Samson, & Winger, 1972).

Qualitatively different activities have beeninduced by the same and other schedules thatare not necessarily temporal or by changes inthese schedules. Introduction of a high fixed-ratio requirement or a fixed-interval schedulecan reliably produce biting of a bar by a re-strained squirrel monkey (DeWeese, 1977;Hutchinson, Azrin, & Hunt, 1968) or attack onanother pigeon by an unrestrained pigeon(Gentry, 1968). In these studies, aggression oc-curs when the work requirement is increasedor when reinforcement density is otherwisedecreased. The limiting case is extinction,

19

1982, 38, 19-34 NUMBER I (JULY)

FREDERICK RAYFIELD et al.

when the work requirement tends toward aninfinity limit and the reinforcement deliveredtends toward a zero limit (e.g., Azrin, Hutchin-son, & Hake, 1966; Reynolds, Catania, & Skin-ner, 1963; Rilling & Caplan, 1973). Schedulesor schedule changes or other conditions identi-cal to those producing aggression will insteadproduce escape, if the enclosure is sufficientlylarge; indeed, even when the enclosure is small,the pigeon will peck a key that turns off thediscriminative stimulus associated with theschedule (Brown & Flory, 1972). Aside from in-duction under conditions of positive reinforce-ment, aggressive and escape patterns are alsoinduced by administration of such noxiousstimuli as painful electric shock (Azrin, Hutch-inson, & Hake, 1963; Ulrich & Azrin, 1962) anda physical blow (Azrin, Hake, & Hutchinson,1965), among other noxious stimuli. The samenoxious stimulus that can induce aggressionwhen the enclosure is small, or escape when itis large, can apparently also induce sexual as-sault on a female rat by a male (Caggiula,1972; Caggiula & Eibergen, 1969).In both open field studies (Hall, 1934) and

the conditioned suppression or conditionedemotional response (CER) studies (Estes &Skinner, 1941) and elsewhere, defecation hasbeen considered an indicator or concomitantof stress.

In the present series of experiments, we re-port the reliable induction of defecation underspecifiable interval schedules, its reliable ab-sence under other interval schedules, and itsabsence under fixed-ratio schedules, even whenthe rat's own response rate spaces the time be-tween deliveries of food to be equal to intervalsthat reliably induce defecation when the sched-ule is an interval one.

EXPERIMENT 1DEFECATION INDUCED BY FIXED-

AND VARIABLE-INTERVALSCHEDULES WITH FOOD

AND WATER REINFORCERS

METHOD

SubjectsTwelve experimentally naive male albino

Holtzman rats served. They were approxi-mately 90 days old and weighed 283 to 311 gat the beginning of the experiment. Six ratswere food-deprived to 90% of previous ad lib

body weight. They had free access to water intheir home cages. The other six rats werewater-deprived to 90%, body weight. They hadfree access to food in their home cages. All sub-jects were given access to food and water forsufficient time periods immediately after ses-sions to maintain them at 90% (±5%) of theiroriginal body weights. Each group of six washoused in a standard clear plastic cage in atemperature-controlled area (24-290 C) witha 12-hour-dark/ 12-hour-light cycle.

ApparatusTwo experimental chambers were used. Each

was 21 cm by 23 cm by 26 cm high constructedof half-inch (1.27 cm) galvanized mesh. Eachchamber was equipped with a 3 cm by 4 cmaluminum lever located 10 cm from the floorand operated by a downward force of .25 new-tons. For the six food-deprived rats, a cup 10cm to the left of the lever provided access to a27-mg Noyes Formula A pellet when appropri-ate. For the six water-deprived rats, a cup inthe same position provided access to .015 ml ofwater from a dipper when appropriate. Thechambers were located in sound-attenuatingcabinets in which a ventilating fan providedfresh air and a masking noise of 70 to 75 dBthroughout the chamber. A 50-W houselightwas located 25 cm above each chamber. A bolusdetector was mounted below each chamber.This consisted of an aluminum funnel in theshape of an inverted pyramid with apex 25 cmbelow the floor of the cage. A photocell at theapex opening detected boli that fell through.At the end of each session, automatic countsfrom the photocell were compared with man-ual counts of boli in the receptacle at the bot-tom of the funnel and of boli adhering to thefunnel walls and mesh floor. The photocellapparatus was found to record, over all ses-sions, an average of 80% of the hand counts.Adhesion of some boli to funnel sides and meshfloor occurred for food-deprived subjects withunlimited access to water in the home cage.The sources of inaccuracy for water-deprivedsubjects were small hard boli that ricochetedaround the photobeam, or were too small tobe detected. (An improved bolus detector isdescribed in the third experiment.)

Solid-state programing equipment was usedto record lever presses and boli and to controldelivery of reinforcers. Lever presses, reinforcerdeliveries, and counts of boli detected were

20

SCHEDULE-INDUCED DEFECATION

recorded on Gerbrands C3 cumulative record-ers; automatic and manual counts of boli wereentered in data logs after each session. A three-channel event recorder was used to recordbolus droppings classified into those that oc-curred three seconds or less before a lever press,those occurring within three seconds after alever press, and those occurring in the remain-ing portion of time.

Experimental ProcedureAll sessions lasted 30 minutes and occurred

within the first six hours of the daily 12-hourlight period, with a few exceptions. Initially,each rat received two to four days of magazinetraining and hand shaping to press the lever ona fixed-interval one-second (FI 1-sec) schedule-virtually a continuous reinforcement sched-ule (CRF). After this initial training, each ratwas exposed to an A-B-C-A-C-A sequence ofschedules, where A was three or four sessionsof FI I-sec, B was three sessions comprising onesession each in the progression, FI 4-sec, FI8-sec, and Fl 16-sec, and C was seven or eightsessions of Fl 32-sec. For one rat (P4), the finalseries of FI 1-sec sessions (Series A) was ex-tended to seven sessions for a direct comparisonwith the preceding seven sessions of Fl 32-sec(Series C). Although no new schedule was in-troduced until the operant had stabilized,fewer sessions of stable FI 1-sec performancewere run than other schedules because this re-inforcement-dense schedule rapidly tended toresult in body weight increases beyond the90% deprivation weight.

Following the A-B-C-A-C-A sequence offixed-interval schedules, a D-A sequence wasadded for three food-deprived rats, and threewater-deprived rats who were randomly se-lected from each group of six. Series D con-sisted of seven sessions on a variable intervalschedule of 32 seconds average (VI 32-sec), witha 2-second minimum and no maximum inter-val; it was achieved by sampling a probabilitygate every two seconds with the probability setat .0625. The final condition (A) was four orfive sessions of FI 1-sec. The same reinforcerswere delivered throughout.

RESULTSCumulative DefecationThe sequence of procedures used and boli

dropped are depicted in Figure 1 for alltwelve rats. For Rats PI-P6 (P represents pel-

let), food was the reinforcer, and for RatsW1-W6, water was the reinforcer. Each unit onthe abscissa represents one 30-minute session,and curves represent boli dropped per session,cumulated within each session and for all likeschedule sessions in a series.As is evident in Figure 1, high rates of defe-

cation were mainly induced on FI 32-sec andVI 32-sec. Upon exposure to the novel appa-ratus, six of the twelve rats did not defecate.Three of the pellet-reinforced (PRF) rats (P1,P2, and P4) dropped only one bolus each dur-ing the first session; one of these three rats(P1) and a fourth rat (P3) dropped two to threeboli during the second session. No PRF ratdefecated during the last training session. Thetwo water-reinforced (WRF) rats who defe-cated during training dropped two boli eachduring all training sessions. One rat (WI)dropped these during the third training ses-sion, and the other rat (W2) dropped themduring the first.The training sessions were followed by three

or four sessions during which an FI 1-sec sched-ule was in effect, and there was no defecationfor any of the six PRF rats nor for four of thesix WRF rats. The remaining rats, W4 andW3, dropped comparatively few boli on Fl1-sec.One session each at FI 4-sec, Fl 8-sec, and Fl

16-sec followed and none of the twelve ratsdropped any boli during the Fl 4-sec session.Three of the rats (P5, P6, and W4) droppedthree boli each during the Fl 8-sec session.Four rats (P2, P5, P6, and W4) dropped twoto five boli each during the FI 16-sec session.During all the Fl 32-sec sessions, the PRF

rats defecated markedly and defecation wastypically absent during the FI 1-sec sessionsthat followed each Fl 32-sec series. For thethree PRF rats for whom VI 32-sec was added,defecation increased, from 4.0 boli dropped persession on the FI 32-sec schedules to an aver-age of 6.6 boli dropped per session of VI 32-sec.The WRF rats defecated more often than didthe PRF rats in the FI 1-sec sessions and defe-cated less than PRF rats in the FI 32-sec andVI 32-sec sessions. For the WRF rats, there wasno corresponding increase over FI 32-sec whenVI 32-sec sessions were added.

Defecation also appeared to be sensitive toschedules of daily running. On the second dayof the first FI 32-sec series, all sessions for PRFrats were unavoidably delayed for six hours.

21


INTERVAL RATS:Food Reinforcement

lPA FlIF-FiS- F/1 P132 Fl/

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SCALE

20

Sessions

Fig. 1. Number of fecal boli dropped each session cumulated over each experimental treatment period for ratspressing a lever on various interval schedules of reinforcement with delivery of food (upper panels) or water(lower panels) as a reinforcer.

Rats P1 and P5 did not defecate at all, andRat P4 dropped only one bolus. These dayscontrast with the other days on FI 32-sec. Thiswas not apparently due to simple stimuluschange. Usually the schedule of reinforcementwas the prime determinant, not changes ofschedule. Rats introduced to FI 32-sec sched-ules following an Fl 1-sec series defecated dur-ing the first session of each series and thereafterat the high rate that characterized that sched-ule, and when introduced to the first Fl 1-secsession following an Fl 32-sec series, did notdefecate at all-the characteristic pattern ofthat series.

Distributions within SessionsEach 30-minute session was divided into 10

consecutive periods of three minutes each, andthe number of boli detected by the photocellduring each period was recorded. These dataare presented for all twelve rats during all Fl32-sec sessions in Figure 2. For four of the sixPRF rats, defecation tended to be maximalduring the first three-minute period. For theremaining two PRF rats, peak defecation waseither in the second or third period (minutesfour through nine), and the distributions seemflatter. These two rats (P2 and P3) generallydisplayed less overall defecation than did theother four, as is evident in Figure 1.Of the six WRF rats, on the other hand,

only one rat (W2) defecated most during thefirst three-minute period; two rats (W4 andW5) defecated most in the second period. The

I i 1AL.ALl I A6 I L-If I i

M5

22


of defecation appeared relatable to amount ofdefecation; rats who defecate more under oneschedule than another will also tend to defe-cate earlier on that schedule.For PRF rats which defecated frequently,

those boli that were dropped late in the sessiontended to be looser, wetter, and in some casesmore diarrheic than did those boli droppedearly in the session. In Figure 3, a smaller peakof defecation later in the sessions can be seenfor several rats. This may be due to the move-ment of a second portion of fecal matterthrough the colon and the small intestine.

SESSIONFig. 2. Temporal distribution of fecal boli dropped

within all sessions at FI 32-sec for each rat. Sessions are

divided into ten consecutive 3-min periods. In the up-

per six panels, lever pressing was reinforced by foodand in the lower six panels, by water.

distributions of the remaining rats are difficultto characterize. Those WRF rats whose distri-butions seem most similar to those of the PRFrats (W2, W4, and W5) also were the most sim-ilar to the PRF rats in terms of the overall def-ecation presented in Figure 1.

Similar distributions for variable-intervalsessions for the three PRF and three WRF ratsare presented in Figure 3. For all the PRF rats,defecation shifted markedly to the first threeminutes of the 30-minute session. However, forthe WRF rats, the practically flat distributionsdemonstrate a more even distribution of defe-cation throughout the session. In the PRFgroup, the distributions of Rats P4 and P5 are

more skewed to the first period than for RatP6, and overall defecation was least for thisrat. It may be recalled that defecation by PRFrats was greater during VI than during Fl ses-

sions, whereas for the WRF rats such increasewas not found. Apparently, temporal patterns

Temporal Relation to Reinforcementand to Lever Pressing

Schedule-induced polydipsia tends to occurimmediately after reinforcement, often duringa postreinforcement pause (Falk, 1961, 1964).However, no such relation could be observedfor defecation. For all six PRF rats, the 32-sec-ond interval during FI 32-sec schedules wassubdivided into quartiles. Only 16% of thetotal number of boli were dropped during thefirst eight seconds following reinforcement,23%o were dropped during the second quartile,32% during the third, and 29% during thefourth. Distributions for the individual ani-mals were in line with these group data. Datasimilarly grouped for all six WRF rats on Fl32-sec were 26%0 for the first quartile; 22% forthe second; 25% for the third; and 27% forthe fourth.The data with regard to relation to lever

P4 P5 P620- 20- 20-

a

0L 0 I0

20- W4 20 W5 20- W6

0mIS10 ~~~~~~~~~~~10

_ffi]]] @4flfin * n DubStart EndSESSION

Fig. 3. Temporal distribution of fecal boli droppedwithin all sessions at VI 32-sec for each rat run on thisschedule. Sessions are divided into 10 consecutive 3-minperiods. In the upper row, lever pressing was reinforcedby food and in the lower, by water.

23


pressing are similar. For all six PRF rats, 52%of the boli were dropped at a time later thanthree seconds after a lever press and earlierthan three seconds before a lever press. 38%,of the boli were dropped within three secondsbefore a lever press, and 20% were droppedwithin three seconds after a lever press. (Per-centages add to more than 100% as some boliwere dropped both within three seconds aftera response and three seconds before the nextresponse.)Cumulative records of lever pressing were

obtained for each session, with bolus droppingindicated by the event pen. The cumulativerecords obtained were similar to cumulativerecords of operant behavior obtained in otherexperiments and reported as "characteristic"of the schedules. The FI curves displayed the"scallops" characteristic of this schedule, andthe VI curves displayed a steady rate of leverpressing. The clustering of fecal matter at thebeginnings of the session was evident. Sched-ule-induced defecation did not interfere withthe rate or pattern of lever pressing establishedunder an operant schedule related to it.

BRIEF DISCUSSIONThe induction of defecation by Fl 32-sec and

VI 32-sec schedules is a robust effect, occurringin the large majority of subjects and with atleast two different reinforcers. Such defecationwas reliably and promptly halted or producedby introducing a CRF or FI/VI 32-sec sched-ule, respectively. The negative correlation ofamount of defecation to number of reinforcersconsumed is particularly striking. Althoughthe schedules that induced it were temporal,regularity of reinforcement in time alone ap-peared not to be the critical variable since def-ecation was also induced on VI 32-sec and waseven enhanced thereby.

EXPERIMENT 2DEFECATION DURING FIXED

RATIO SCHEDULES WITHFOOD REINFORCERS

The first experiment demonstrated that def-ecation was induced when rats are lever press-ing for food or water on temporal schedulessuch as FI 32-sec and VI 32-sec but not onshorter temporal schedules such as Fl 1-sec.In both Fl and VI schedules, reinforcer deliv-

ery is contingent upon the passage of timeas well as upon the specified response. InFl, distribution of responses within the in-terval is irrelevant to the schedule. However,since the intervals vary in VI, reinforcementdensity is maximized by intervening responses.The contributions of intervening responsesand time interval were experimentally sepa-rated in the following manner. In the secondexperiment to be reported here, the 32-sec timeinterval of FI 32-sec was nearly preserved, butby means of a fixed ratio schedule. Given asteady response rate, an nth response may befound empirically that occurs approximately32 sec after reinforcement, and reinforcementmay be made contingent on that nth responsein a FR-n schedule. Although the FI 32-sectime interval is preserved, n-l intervening re-sponses are required for the counter to recordn and deliver the reinforcer, which is not thecase for Fl 32-sec. In the third experiment (tobe reported subsequently) delivery of food wasmade contingent on the completion of a timercycle alone, irrespective of behavior.

METHODSubjects

Subjects were three experimentally naivemale albino rats of the same strain, sameweight range (289 to 308 g), and same age (90days) as the rats in Experiment 1. Housing andfood-deprivation conditions and procedureswere also similar.

ApparatusThe chamber with pellet dispenser used in

the first experiment was also used for the sec-ond. Control, monitoring, and recordingequipment were also the same.

ProcedureAs before, all sessions lasted 30 minutes.

Lever pressing was hand-shaped with a foodpellet following each response (FR-1). Each ratwas then presented with an ascending series offixed-ratio requirements. There were four ses-sions each of FR-1, FR-2, FR-4, and FR-16, dur-ing each of which response rate and patternstabilized. However, when the ratio require-ment was increased to FR-32 and beyond, leverpressing by all rats did not stabilize in foursessions. Accordingly, additional sessions wererun in a series on an individual basis until sta-bility was obtained. The sole exception to this

24


procedure was for one series, with one rat (R3,first FR-64 series), when eleven sessions wererun with no improvement in stability, and thenext schedule was introduced. The ratios fol-lowing FR-32 were FR-64, FR-80, FR-96 for allthree rats. Two of these rats were also run atFR-128, and one of these was also run at FR-192. For each rat, a series descending from thehighest ratio to FR-1 was then run. This wasfollowed by another ascending series and thena descending series. Two rats were then run onsingle sessions of FR-1, FR-192 or FR-96, andFR-1.

RESULTSThe actual sequence for each rat, the num-

ber of sessions at each ratio series, and the cu-mulative number of boli dropped during eachseries are presented in Figure 4. The numbersin italics indicate the average time in secondsbetween reinforcements in that series; differ-ences between reinforcement rates at the sameratio represent differences in overall responserate.

Cumulative DefecationRat RI (R as in Ratio) almost never defe-

cated during experimental sessions. He did notdefecate at FR-96, when the rate of respondingproduced interreinforcement intervals (IRI) of32 seconds. He did not defecate during any ses-sions ranging from FR-1 to FR-192 thereafter,except for one bolus dropped during the firstFR-192 series (IRI 79 seconds) and one bolusduring the FR-32 series (IRI 13 seconds).Rat R2, as well, almost never defecated on

schedules ranging from FR-1 to FR-96. He didnot defecate during the first FR-48 series whenthe IRI was 28 seconds, nor the followingFR-64 series when the IRI was 39 seconds. Theonly boli he dropped were one in the secondFR-8 series, and one during the fourth FR-16series.Rat R3, in contrast, dropped more boli than

other ratio rats. Defecation was not systematicor reliable, nor was the rate as high as thatinduced on the FI 32-sec schedule in Experi-ment 1. He dropped three boli during the firsttraining session, and none thereafter until thefifth session on FR-64. On this schedule, hepressed the lever about twice per second, re-sulting in an IRI of 38 seconds. He then con-tinued to defecate through the FR-80 series(IRI 58-seconds), dropping an average of 5.2

boli per session. He defecated less during theFR-96 series, dropping an average of 3.5 boliper session. During the following FR-128 series,defecation decreased further and finally ceased.Rat R3 did not defecate when these schedules(FR-64, 80, 96, and 128) were reintroduced. Itwill be recalled that, in contrast, during thoseinterval schedules when defecation was foundto occur, rats defecated whenever those sched-ules were reintroduced.The performance of Rat R3 is anomalous in

other regards as well. Cumulative records oflever pressing for all three rats reflected typicalfixed-ratio performances. The fixed-ratio pat-terns of Rat R3 were the least stable of thethree rats, exhibiting the greatest number ofthose pauses commonly associated with ratiostrain. Rat R3 was also the only rat under aratio schedule which defecated during the ini-tial training period. For Rat R3, no systematicrelation was found between defecation andeither reinforcement or lever pressing.

Distribution of Defecation within SessionsThe distribution of boli dropped by the only

rat who defecated significantly on ratio sched-ules is presented in Figure 5. The boli droppedduring the first FR-64, FR-80, FR-96, and FR-128 series were recorded in ten 3-min bins forall 30-min sessions, as before. This distributiondiffers considerably from the distributions pro-duced under Fl 32-sec by food-reinforced rats(Figure 2). There is no peak at the beginningof the session, nor is there a noticeable ten-dency to drop boli at any other particular timeduring the session.

BRIEF DISCUSSION

It appears that defecation is not generally in-duced by fixed ratio schedules. Where it didappear in one rat, it turned out to be a tran-sient phenomenon; it did not recur when thesame ratio requirements were introduced at alater time. This contrasts with defecation un-der interval schedules, in which it was reliablyand repetitively induced when schedules withwhich it is associated were repetitively intro-duced and was reliably and repetitively elimi-nated when schedules associated with its ab-sence were repetitively introduced.The induction of defecation under both FI

and VI schedules (Experiment 1) suggests thatregularity of interreinforcement intervals is

25

26 FREDERICK RAYFIELD et al.

Rat RI

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SESSIONSFig. 4. Number of fecal boli dropped each session cumulated over experimental treatment periods for rats press-

ing a lever on various fixed-ratio schedules of reinforcement (see Figure 1). Number in italics is the time (in sec-

onds) interval between deliveries of reinforcement, averaged for each treatment.

/6

26

9673


20

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R3

FR 64-128

4fStart End

SESSIONFig. 5. Temporal distribution of fecal boli dropped

for the rat who did defecate within all fixed-ratioschedules during which defecation occurred. Sessionsare divided into 10 consecutive 3-min periods (see Fig-ure 2).

not essential to schedule-induced defecation.Nor is the steady-state regularity of response

rate during VI essential to schedule-induceddefecation since defecation was not inducedunder the regular responding of FR schedulesand was induced under scalloped Fl respond-ing.

EXPERIMENT 3DEFECATION INDUCED BYFIXED TIME SCHEDULESWITH FOOD REINFORCERS

In the first experiment, defecation was in-duced when food or water was contingent on

lever pressing under reinforcement schedulessuch as Fl 32-sec or VI 32-sec, but not at lowerinterval schedules such as Fl 1-sec. In the sec-

ond experiment, defecation was not inducedaccompanying FR schedules in which the in-tervals between reinforcements were similar tothose found in the defecation-inducing Flschedules. The differences between defecation-inducing temporal schedules and interval-com-parable noninducing FR schedules may rest inthe different type of behavior contingenciesholding. On the other hand, they may simplyrest in the difference between presence andabsence of time-dependent interreinforcementintervals. Defecation, like polydipsia, might be

induced simply by delivering food pellets attemporal intervals comparable to those hith-erto sufficient for induced defecation. Suchtimer-governed delivery of food pellets is de-fined as a fixed-time (FT) schedule, in contrastto fixed-interval (FI) schedules where the timergoverns availability of food, and a subsequentexperimenter-defined response is required todeliver it. Experiment 3 compared induceddefecation on FT 32-sec, FlI -sec, and FI 32-sec.

METHODSubjectsSix rats served. Four were experimentally

naive male albino Holtzman rats of the samestrain, weight range (303 to 306 g), and age (90days) as the rats in Experiments 1 and 2. Twowere experimentally naive female albinoSprague-Dawley rats, of lower body weights(259 and 280 g), and same age (90 days) as themales. Housing and food-deprivation condi-tions and procedures were also similar to theprevious experiments.

ApparatusThe chamber with pellet dispenser used in

the first and second experiments was also usedhere. A lever was present in most conditions,but was unrelated to food delivery in the FTconditions. It was removed from the chamberduring one FT condition. Control, monitor-ing, and recording equipment were the same asin previous experiments, except for variationsin lever presence and lever contingencies, asnoted, and except for the substitution of a newbolus detector.A square piece of 20 gauge aluminum served

as a drop-pan under the entire chamber floor,and an inexpensive ceramic phonograph car-tridge was mounted on it. The drop pan restedon foam rubber feet at each of the four cornersand was positioned 15 cm below the chamberfloor. The phonograph cartridge was con-nected to an LM324 operational amplifier,which served as an adjustable trigger. Withthis detector it was possible to set the triggerto ignore urine droppings, but to record virtu-ally all boli dropped.The new bolus detector detected 98% of boli

dropped, in contrast to the 80% detected bythe earlier one.Cumulative records were kept of lever press-

ing in each session (whether the lever was func-tional or not), as well as counts of lever presses,

27


food-pellet deliveries, and boli dropped. Aspreviously, hand counts of boli were taken toverify and supplement automatic bolus de-tection.

ProcedureAll sessions lasted 30 minutes, as before. For

the four male rats (Tl to T4), the first blockconsisted of ten sessions in which a 37-mg foodpellet was automatically delivered every 32seconds (FT 32-sec). The second block con-sisted of four or five sessions of FlI -sec. Handshaping of lever pressing occurred during thefirst Fl 1-sec session but required only five toten minutes of the 30 min session. Upon com-pletion of the second block, two rats (T2 andT3) were withdrawn from the experiment inorder to be used in a different one. For the tworemaining, the ensuing design involved alter-

nating blocks of seven or eight FT 32-sec ses-sions with blocks of seven or eight Fl 32-secsessions. The lever was removed for the finalFT 32-sec series for both rats. The order andnumber of sessions in each series is shown inFigure 6.The two female rats (T5 and T6) each re-

ceived ten sessions of FT 32-sec. The experi-ment was then interrupted for 79 days, duringwhich the rats were fed and watered ad lib.They were then deprived to 90% body weight.For Rat T5, FT 32-sec was continued for 18sessions, followed by four sessions of FT 256-sec. For Rat T6, deprivation was followed by22 sessions of FT 32-sec.

RESULTSThe detailed sequence for each rat, the num-

ber of sessions at each series, and the number

FT-32o. 79 day break

SESSIONSFig. 6. Number of fecal boli dropped each session cumulated over each experimental treatment period for all

rats to whom food was presented at fixed-time periods (FT 32-sec), or for whom food was available at simrilar (Fl32-sec) temporal intervals, or those lower (Fl I-sec), but with a depressing of a lever then necessary for food deliv-ery (see Figures 1 and 2).

28


of boli dropped per session cumulated for eachseries are presented in Figure 6.

Cumulative DefecationFor Rat TI, boli were dropped during FT

32-sec and FI 32-sec, in almost indistinguish-able patterns or rates. In contrast, once leverpressing was established, there was little defe-cation during the FI 1-sec sessions. In all thefollowing FT 32-sec series and FI 32-sec series,defecation resumed at high rates. Removal ofthe lever in the terminal FT series had no dis-cernible effect on defecation.

For Rat T2, the difference between FT 32-sec and Fl 1-sec was even more pronounced.The FT 32-sec produced regular, moderatedefecation. The FI 1-sec series was character-ized by no defecation except during the Fl1-sec training session.

Rat T3 dropped four boli in the first FT32-sec session, did not defecate during the nextthree sessions, and then resumed defecating forthe rest of the FT 32-sec sessions at a rate com-

parable to Rats TI and T2. Like Rat TI, hedefecated infrequently (two boli) during thefirst (and only) training session, and did not

defecate during the three Fl 1-sec sessionsthereafter.Rat T4 dropped only two boli during the

ten sessions of the first FT 32-sec series. No boliwere droppedc during the three FI 1-sec andfour FT 32-sec sessions that followed. Regulardefecation began in the next series, FI 32-sec.Thereafter, defecation in FT 32-sec and Fl 32-sec sessions replicated the patterns of the otherthree male animals on these schedules. Simi-larly, removal of the lever in the last FT 32-secseries had no discernible effect on defecation.

After eight sessions of no defecation, Rat T5,a female, defecated during two sessions of FT32-sec. After a break of 79 days, the FT 32-secseries was resumed. The previous pattern was

almost replicated: there were seven sessionswithout defecation, with defecation occurringthereafter. The rate of defecation increasedgradually, with eight boli dropped during Ses-sion 25. A series of four FT 256-sec sessions wasthen run with no decrease in defecation.For Rat T6, like T5, early sessions were de-

void of defecation. There was no defecationduring the ten sessions preceding the 79 daybreak, nor during thirteen sessions on FT 32-

sec that followed. Thereafter, modest defeca-tion began.

Distribution of Defecation within SessionsEach 30-minute session was divided into 10

bins of three minutes each, and the number ofboli dropped during each three-minute unitwas recorded. The distributions for Rats TIto T6 are presented in Figure 7. The distribu-tions of defecation for rats on FT 32-sec didnot differ appreciably from distributions seenon Fl 32-sec in this experiment and in thefirst experiment. For Rat TI, all four FT 32-secseries are combined. The concentration ofbolus droppings (35%O of the total) during thefirst three minutes is marked; the distributionseems to have an additional pair of progres-sively smaller peaks thereafter. That the over-all data are typical of individual series can beseen by comparison with the distribution of thefirst FT 32-sec series alone in the adjacent dis-tribution. About 40% of the boli were droppedin the first three-minute period, and there aretwo "peaks" thereafter. The distribution forall the FI 32-sec series for this rat does not ap-preciably differ: about 28% of all boli weredropped in the first three minutes of all Fl32-sec sessions with two "peaks" thereafter.Rat T2 dropped too few boli in any period

to describe any characteristic distribution withconfidence. However, Rat T3, even with a lim-ited number of sessions, displayed a "peak"during the first three minutes, when about40% of the boli were dropped.

For Rat T4, the distribution for all four FT32-sec series combined is presented; 23% of allboli were dropped during the first three min-utes, and an additional 30% were dropped inthe next three, with over half of the boli (54%)accounted for during the first six minutes ofthe 30-minute session. The individual distri-butions for each FT 32-sec series (except thefirst series, which produced only two boli) simi-larly display an increasingly marked peak ineither the first or second three minutes as seenin Distributions B, D, and F. The first FI 32-secseries for this rat was characterized by very lit-tle defecation (see Distribution A), but as defe-cation increased during the second and thirdFl 32-sec series (Distributions C and E), thetypical "peak" became evident early in thesession.

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FT32 FT32-(all b)d

30-~ ~ ~ ~~1

30~~~~~~

20-

10 10 A

0Start EndSESSION.

Fig. 7. Temporal distribution of fecal boli dropped withare then divided into 10 consecutive 3-min periods.

The distribution of boli dropped by femaleRat T5 is also marked by a "peak" early in thesession-centered, however, in the third three-

F132

10 C

0hLJ

FT32

10 F

:' 1

F132

0flj10I

Un FT 32-sec and FI 32-sec series for each rat. Sessions

minute period (35%0 dropped that period).Again, there is mild evidence for a secondpeak. The number of boli dropped by this rat

30


during sessions on FT 256-sec, as shown, is in-sufficient to ascribe any particular pattern. Theother female, Rat T6, defecated so infre-quently that no statements can be made abouther distribution.

Temporal Relation to Reinforcementand Lever PressingNo temporal relation between the delivery

of food pellets and defecation was observed forany of the subjects in this experiment. Simi-larly, there was no observable relation of defe-cation to lever pressing. For example, the firstseries for Rat TI was an FT 32-sec series. Theoperant level of lever pressing for each day inthis series decreased from 42 to about 5 persession. Defecation appeared to be unrelatedto those lever presses. An FI 1-sec requirementwas then imposed on the free-operant level.When FT 32-sec was reintroduced, the leverwas again nonfunctional. The number of leverpresses for each of the FT 32-sec sessions was151, 50, 42, 32, 20, 11, 15, and 23, with the ini-tially highest rate probably reflecting the his-torical effects of the preceding fixed-intervalsessions, and the decreasing rates thereafterreflecting extinction of the response under anFT schedule. The first Fl 32-sec series followed,and typical scalloped lever pressing was quicklyestablished. During the next FT 32-sec series,the number of lever presses per session was 195,134, 114, 167, 74, 109, 86, and 82, again re-flecting both history and extinction. No leverwas present during the final FT 32-sec series.In no condition could the experimenter de-tect a relation between defecation and leverpressing.For Rats T2 and T3, there also appeared to

be no relation between free-operant lever press-ing and number of boli dropped per session.For example, the operant levels of lever press-ing during FT 32-sec series (and number ofboli dropped per session in parentheses) were26(0), 8(3), 17(2), 28(1), 41(0), 18(3), 26(4),14(2), 14(3), and 27(4), 23(0), 17(0), 29(0), 16(2),27(1), 30(4), 25(1), 16(4), 16(5), respectively. ForRats T5 and T6 the number of free-operantlever presses was less than 20 during each ses-sion of FT 32-sec. These, too, appeared unre-lated to defecation.

Finally, subjects were observed in some casesto lever press and defecate simultaneously.

BRIEF DISCUSSIONFrequency of defecation under the fixed-time

schedules used, once started, did not differappreciably from that holding under fixed-interval schedules with identical time param-eters. The distributions of defecation withinan FT session were also similar to those seenin an FI session, displaying the same high peakearly in the session, followed by smaller peaksthereafter.The major difference between time and in-

terval schedules seemed to be in the numberof sessions required for defecation to start.This statement holds especially for three rats(T4, T5, T6) and possibly a fourth (T3). InExperiment 1, involving only interval sched-ules, the onset of defecation was also delayedfor many rats, especially those whose rein-forcement was water. The differences in onsetbetween time and interval performances ap-peared, then, to be one of degree. Once estab-lished, the pattern seemed to be strong ineither case.

EXPERIMENTS 1 TO 3OTHER OBSERVATIONS OF

SUBJECTS' BEHAVIORDefecation has been related to emotionality

in the general literature. Accordingly, the be-havior of the rats outside of the experimentalchambers and within them is worthy of note.

HousingRats defecated freely in their home cages.

The litter was changed every three days, andboli were counted. In the male housing units,an average of 25 to 30 boli per rat was foundfor each day. In the females' cages, the corre-sponding average was about 18 to 25 boli. Dur-ing sessions, when defecation was induced, ratsgenerally dropped between 3 to 6 boli, al-though as many as 12 boli were dropped in onesession. Boli dropped later in a session tendedto be extremely moist and unformed. Diarrheawas observed in many cases. On days whendefecation-inducing schedules were in effect(Fl 32-sec, VT 32-sec, FT 32-sec), from about12% to 50% of a rat's daily boli were droppedduring the 2.1% of the day represented by a30-minute experimental session.

31


General DispositionThe demeanor of the rats was seldom aggres-

sive. Rather, when the experimenter ap-

proached the home cages to transport a rat to

the experimental chamber, all rats immedi-,ately crowded to the front of their units, rais-ing themselves and poking their noses throughthe bars. They scrambled over each other to

climb into the experimenter's hand. Oncethere, if released, they climbed over his arm or

explored him in other ways. After weighing,the rats hopped out of the pan with alacrity.As the experimental chamber was approached,they struggled to escape the experimenter'shand and to.enter the chamber. At the end ofthe session when the experimenter reached hishand into the chamber to remove the rat, therat would typically cling to the mesh floor or

mesh wall furthest from the experimenter'shand. No rat ever bit the experimenter at thistime.

EmotionalityThe rats were observed and photographed

during sessions when they defecated and atother times. There were none of the responses

from which emotionality is generally inferred:there was no piloerection, rigidity, crouching,nor suppression of lever pressing. As previouslynoted, rats occasionally defecated while press-

ing a lever (and have been photographed).Such behavior was not uncommon, especiallyduring sessions of VI 32-sec, but the majorityof the boli were dropped while the animal was

eating, grooming, or exploring. None of theseactivities is compatible with an inference ofemotionality.

GENERAL DISCUSSIONWe report in these experiments the system-

atic induction of a pattern of behavior which,when reported elsewhere, has generally beenassigned to emotionality under stressful condi-tions. The conditions so labeled have beeneither initial exposure to a novel situation,such as the "open field" test (e.g., Hall, 1934),or the presentation of an aversive or preaver-sive stimulus. In our experiments, defecationwas induced during ordinary schedules of rein-forcement in the absence of either the condi-tions associated with stress or other responses

assumed to indicate it. As judged by the de-meanor of our rats, the experimental chamberwas not a place of stress, nor was it a conditionthat occasioned avoidance behavior. The ratsdid not, as they typically do in CER experi-ments, withdraw to the back of their homecages when approached, nor struggle againstbeing picked up, nor bite the extended handof the experimenter, nor fight being placed inthe experimental chamber. The behavior ofthe rats run in our experiments was the oppo-site. Yet they defecated, and often profusely,in the experimental chambers when underthose schedules often used to maintain baselineresponding in conditioned suppression (CER)experiments. Their defecation was not accom-panied by rigidity, piloerection, nor other re-sponses presumably related to stress. Indeed,very little defecation occurred during their ini-tial exposures to the novel chamber, and suchdefecation as did then occur was not accom-panied by the other emotional concomitants ofthe open field test. The question is raised as tothe extent to which defecation as a sign ofemotionality in a CER paradigm (as opposedto a reflex response to shock) is in part an ad-junct to the reinforcement schedule used tomaintain the operant whose suppression isbeing studied.The defecation-inducing schedules of our

experiments typify those used to induce poly-dipsia (Falk, 1961). The conditions underwhich one schedule-induced behavior is foundrather than the other, or both, or neither, havenot been investigated, nor are they the subjectsof the research presented to date. It is also ofinterest that the schedules that do not typicallyinduce polydipsia (fixed-ratio and low-fixedintervals) also do not induce defecation. How-ever, the occurrence of defecation by Rat T6under a few sessions of FT 256-sec suggests thatdefecation may continue to be induced bythose long intervals under which polydipsia isattenuated.

It is clear that under the conditions of theexperiments presented, deliveries of a stimulusmade potent by deprivation are sufficient toproduce defecation if the intervals betweendeliveries are governed by time, with (FI) orwithout (FT) an experimenter-defined re-sponse requirement for such delivery. A varietyof activities occur during an experiment thatare ancillary to the operant under investiga-

32


tion. Schedule-induced behavior may be one ofthese and, when it does come to attention,should not be assumed to be the only one ofthese. It may be the case that in an FT session,in whichreinforcement is not contingent on an

experimenter-defined operant but, rather, isstrictly governed by a timer, behavior ancillaryto the defined-as-unnecessary operant does sys-

tematically precede reinforcer delivery [pos-sibly as defined by the organism; e.g., reachingfor the experimenter-delivered reinforcer (cf.Skinner, on "chained reflexes," 1938, pp. 102-108)], thereby functionally reinstating an Flschedule (Note 1). Although the possibility re-

quires experimental demonstration, it should,nevertheless, be noted that with regard to defe-cation, the interreinforcement spacing that in-duced defecation in fixed- and variable-intervalschedules and fixed-time presentations did notinduce defecation when the equally spaced de-liveries were under the governance of previousresponses, as in fixed-ratio schedules.

It appears that the defecation that is so in-duced is not simply the result of a gastrocolicreflex to food or water intake. If it were, itwould have been expected all the more

strongly under schedules such as FI I-sec, as

well as small fixed ratios, when rate of foodintake was high. Under larger FR schedules,reinforcement density was often as low as itwas under FI and VI schedules with deliveriessimilarly spaced. Nevertheless, there was notsystematic defecation under the FR schedules,but there was such defecation under the tem-poral schedules (FI, VI, and FT). Therefore,a reflex to infrequent presentations of food tothe alimentary canal is an insufficient explana-tion. Furthermore, although concentrated atthe beginning of temporal sessions, defecationcontinued throughout the session, with eachbolus becoming progressively softer. Several ofthe rats on Fl 32-sec and VI 32-sec droppeddiarrheic stools. These data are not consistentwith an interpretation of the defecation as a

normal gastrocolic reflex.It has been argued that one characteristic

differentiating the schedules or conditions in-ducing polydipsia from those not inducing it(which held for defecation in the present series)is the availability of free time for alternativeactivities. In the low interval schedules, thistime is presumably occupied by lever pressing,as it is in the ratio schedules. It is under the

temporal schedules of time presentations thatanimals may presumably find the time to en-gage in polydipsia, or defecation, or, for thatmatter, exploring the territory of another rat(Davis & Wheeler, 1966). However, as Falknoted (1961), and as can be observed from ourcumulative records, time is available for alter-native activities during the low FI schedulesand on the ratio schedules. Further, the VIschedules may be as "crowded" with operantbehavior as are FR schedules. Finally, the ob-servation that defecation and lever pressingoccurred simultaneously suggests that avail-ability or lack of opportunity due to patternsof ongoing scheduled operants is not a plausi-ble explanation.By virtue of its association, possibly artifac-

tual or reflexive, with stressful conditions andstress-suggestive behavior, excessive defecationhas been considered to be a sign of stress. Ac-cordingly, treatment of such human syndromesas the irritable colon syndrome has often beenaddressed to presumed stressful conditions orlife styles and the emotional reactions that ac-company them. To the extent that extrapola-tions may be made from the present experi-ments (as they have been from others), theysuggest that schedules of positive reinforce-ment as they relate to temporal governance,may be involved. Indeed, Brady et al. notedsome time ago (1958) that the "executive mon-keys" whose lever pressing postponed deliveryof shock for themselves, and their yoked con-trols succumbed from perforated ulcers onlywhen specific time periods governed the in-statement and withdrawal of the experimentalnondiscriminated avoidance conditions.The foregoing experiments are presented to

report initial explorations and findings, ratherthan to be definitive. Research presently underway will report extensions to other schedule-induced patterns, to other schedules, and toother procedural parameters.

REFERENCE NOTE

1. The authors are indebted to Paul Andronis andT. Joe Layng for help in clarifying this point.Since the writing of this article, Rayfield has experi-mentally demonstrated scalloped responding of thetype found in Fl schedules, under FT schedules. Theancillary behavior recorded was nose or paw opera-tion of a cover to the food magazine. A poster ses-sion of the experiment was presented at the 1981

33


annual meeting of the Association for BehaviorAnalysis, Milwaukee, entitled: Operant Respondingon FT Schedules.

REFERENCESAzrin, N. H., Hake, D. F., & Hutchinson, R. R. Elicita-

tion of aggression by a physical blow. Journal of theExperimental Analysis of Behavior, 1965, 8, 55-57.

Azrin, N. H., Hutchinson, R. R., & Hake, D. F. Pain-induced fighting in the squirrel monkey. Journal ofthe Experimental Analysis of Behavior, 1963, 6, 620.

Azrin, N. H., Hutchinson, R. R., & Hake, D. F. Extinc-tion-induced aggression. Journal of the Experimen-tal Analysis of Behavior, 1966, 9, 191-204.

Brady, J. V., Porter, R. W., Conrad, D. G., & Mason,J. W. Avoidance behavior and the development ofguetr6duodeml ulcers. Journal of the ExperimentalAnalysis of Behavior, 1958, 1, 69-72.

Brown, T. G., & Flory, R. K. Schedule-induced escapefrom fixed-interval reinforcement. Journal of theExperimental Analysis of Behavior, 1972, 17, 395-403.

Caggiula, A. R. Shock-elicited copulation and aggres-sion in male rats. Journal of Comparative and Phys-iological Psychology, 1972, 80, 393-397.

Caggiula, A. R., & Eibergen, R. Copulation of virginmale rats evoked by painful peripheral stimulation.Journal of Comparative and Physiological Psychol-ogy, 1969, 69, 414-419.

Davis, H., & Wheeler, L. Social interaction betweenrats on different schedules of reinforcement. Psycho-nomic Science, 1966, 4, 389-390.

DeWeese, J. Schedule-induced biting under fixed-in-terval schedules of food or electric-shock presenta-tion. Journal of the Experimental Analysis of Behav-ior, 1977, 27, 419-431.

Estes, W. K., & Skinner, B. F. Some quantitative prop-erties of anxiety. Journal of Experimental Psychol-ogy, 1941, 29, 390-400.

Falk, J. L. Production of polydipsia in normal ratsby an intermittent food schedule. Science, 1961, 133,195-196.

Falk, J. L. Studies on schedule-induced polydipsia. InM. J. Wayner (Ed.), Thirst: First international sym-posium on thirst in the regulation of body water.New York: Pergamon Press, 1964.

Falk, J. L., Samson, H. H., & Winger, G. Behavioralmaintenance of high concentrations of blood ethanoland physical dependence in the rat. Science, 1972,177, 811-813.

Gentry, W. D. Fixed-ratio schedule-induced aggression.Journal of the Experimental Analysis of Behavior,1968, 11, 813-817.

Hall, C. S. Emotional behavior in the rat. Journal ofComparative Psychology, 1934, 18, 385-403.

Hutchinson, R. R., Azrin, N. H., & Hunt, G. M. Attackproduced by intermittent reinforcement of a con-current operant response. Journal of the Experimen-tal Analysis of Behavior, 1968, 11, 489-495.

Mendelson, J., Zec, R., & Chillag, D. Schedule depen-dency of schedule-induced air-licking. Physiologyand Behavior, 1971, 7, 207-210.

Reynolds, G. S., Catania, A. C., & Skinner, B. F. Con-ditioned and unconditioned aggression in pigeons.Journal of the Experimental Analysis of Behavior,1963, 6, 73-74.

Rilling, M., & Caplan, H. J. Extinction-induced ag-gression during errorless discrimination learning.Journal of the Experimental Analysis of Behavior,1973, 20, 85-92.

Skinner, B. F. The behavior of organisms. New York:Appleton-Century, 1938.

Ulrich, R. E., & Azrin, N. H. Reflexive fighting in re-sponse to aversive stimulation. Journal of the Exper-imental Analysis of Behavior, 1962, 5, 511-520.

Received February 4, 1980Final acceptance March 11, 1982

Documents

SCHEDULE-INDUCED DEFECATION FREDERICK RAYFIELD