Physiology & Behavior, Vol. 22, pp. 379--381. Pergamon Press and Brain Research Publ., 1979. Printed in the U.S.A.

Polydipsia in the Monkey Generated by Visual Display Schedules

ROBYN H U D S O N A N D G E O R G E S I N G E R

Department of Psychology, La Trobe University, Bundoora, Victoria, Australia, 3083

(Received 14 July 1978)

HUDSON, R. AND G. SINGER. Polydipsia in the monkey generated by visual display schedules. PHARMAC. BIOCHEM. BEHAV. 22(2) 379-381, 1979.--Discussions of adjunctive behavior still largely refer to polydipsia induced by food delivery schedules to food deprived animals. In the present experiment polydipsia was induced when socially isolated monkeys housed in barren home cages were exposed to scheduled deliveries of film and scheduled viewing of other monkeys. These data suggest the greater generality and complexity of adjunctive behaviors and show that schedule- induced polydipsia cannot be regarded as an artifact of food associated drinking.

Polydipsia Visual display schedules Monkeys

SERIOUS interest in schedule-induced or adjunctive behav- iors began with the report [7] that water satiated but body weight reduced rats will drink copious quantities of water when placed in a Skinner box on a VI-1 rain food delivery schedule. The occurence of apparently bizarre behaviors had been briefly mentioned in earlier literature on operant condi- tioning (eg. [3, 17]) but since such behaviors were peripheral to the main concerns of the investigators, they were largely disregarded.

The type of adjunctive behavior displayed depends on available stimuli [4]. Excessive drinking or polydipsia, and other behaviors such as bar biting, pica and increased groom- ing and locomotion have been induced by fixed and variable interval schedules and by contingent and non-contingent schedules [18]. The schedule-induced behavior receiving greatest attention has been polydipsia, probably because drinking is a discrete behavior and water intake easily meas- ured. With only few exceptions the control schedule has consisted of contingent or non-contingent food delivery to body weight reduced aniamls. Thus discussion of adjunctive behavior still largely refers to polydipsia induced by the scheduled delivery of food to food deprived animals.

Although the rat is the most commonly used animal, schedule-induced behaviors have been established in mice [11], pigeons (eg. [14]), monkeys (eg. [5]) and humans (eg. [9,20]). Polydipsia has been induced in food deprived mon- keys placed on food delivery schedules [13] and has been shown to be dependent on the delivery interval [1]. The possibility of shifting the control schedule from the delivery of a food pellet to an auditory stimulus which has been pre- viously paired with food delivery has also been demon- strated using monkeys [12].

Studies using humans show that the range of schedule controlled behaviors may be extensive and that the inducing schedule need not be food delivery. In experiments using scheduled penny delivery [9,10] it was found that subjects

developed various adjunctive behaviors including pacing and polydipsia. It has also been shown that adjunctive behaviors may develop under conditions of scheduled game playing [20] and maze tracing [19].

As studies using humans and rats [16] have shown that a range of schedule induced behaviors, including polydipsia, can be elicited by schedules other than food delivery and in non-deprived organisms, in the present study the drinking behavior of free feeding weight monkeys was observed dur- ing visual display schedules.

It has been demonstrated [2] that monkeys shut inside a featureless cage will work hard for a view of the world out- side the cage. These data strongly suggest that monkeys are activated by changing visual displays and that monkey curiosity may be a powerful promoter of learning. Of the various stimuli the monkeys could work to view, the sight of another monkey was the strongest incentive. Studies of pri- mate development [8] and the effects of isolation rearing also indicate that monkeys are fundamentally social aniamls.

These findings suggested the possibility of inducing polydipsia by exposing socially isolated monkeys housed in barren home cages to various visual display schedules.

METHOD

Animals

Three sub-adult crab-eating macaques (Macaca fas- cicularis) weighing approximately 3 kg each were used. These animals were visually isolated from each other in in- dividual home cages several days before testing and except for the sight of laboratory staff at feeding, cleaning and catching times, could view only the bare home cage walls. They were provided with ad lib home cage food and water throughout the experimental period. Two of the monkeys had been used in previous adjunctive behavior experiments. They had been food deprived and run on bar-press contin-

Copyright © 1979 Brain Research Publications Inc.--0031-9384/79/020379-03502.00/0

380 HUDSON AND SINGER

gent FI-1 min and FI-2 min food delivery schedules for 1 1oo

hour daily for several weeks. The third monkey had not been used in any previous experiment. 8o

Procedure ~ 6o E

In the first experiment animals were restrained in a "Plas - Labs" primate chair fitted with a drinking tube. They were -~ 2 40 tested in a dark room for 1 hour at the same time each day _~ and exposed to FT-1 min 10 sec delivery of the films "Pri- mate Growth and Development" (Appleton-Century-Crofts) ~ 20 and "Imprint ing" (A.C.C.). Twenty-three hr home cage water intake and 1 hr experimental session water intake were recorded daily.

Two baseline control conditions were also run. In an at- tempt to control for possible boredom effects water intake was measured while animals were chaired in the dark for 1 FIG. hr; and in an attempt to control for possible film effects water consumption was measured while aniamls were chaired and exposed to continuous f'dm for 1 hr. Both baseline conditions were run before the introduction of schedule sessions and were also interspersed between schedule sessions. Thus animals were tested for 1 hr each day, either under a baseline or schedule condition, and each animal was its own control.

In the second experiment the schedule was changed to ~ 60

FT-1 min 10 sec delivery of light during which the so- E cially isolated animal could view a stimulus monkey chaired ~ ~° i close beside him. Two different monkeys were used on sepa- ~ 1 rate occasions as stimuli for each experimental animal. Each ~ i of the three monkeys served on various occasions as both ~ 20i experimental animals and stimulus aniamls. t There were three baseline conditions. During one baseline condition water intake was measured while experi- mental and stimulus monkeys sat side by side in constant dark for 1 hr. In a second baseline the monkeys sat side by side in constant light for 1 hr; while during a third baseline animals were chaired alone for 1 hr during scheduled light delivery. These baselines were run before the introduction of so scheduled monkeys viewing sessions and were interspersed between them. Animals were tested for 1 hr each day in either a baseline or experimental session, and each animal was its own control.

Water intake for one animal was recorded during sched- uled viewing of a stimulus monkey after the animal 's home cage social isolation was ended. The non-deprived monkey was tested under schedule and baseline conditions for sev- eral days and then home cage social isolation was re- established. The re-isolated monkey continued to be tested under schedule and baseline conditions for several days and then home cage isolation was ended a second time and the monkey run for several more days under schedule and baseline conditions.

R E S U L T S

Scheduled Film Delivery

Figure l shows water consumption for the monkey " Jonesy" during baseline and experimental conditions of scheduled f'dm delivery. Drinking during both the continuous dark and continous film baselines was negligible and never exceeded 5 mls and a Mann-Whitney U test [6,15] showed there was a significant difference between experimental and baseline condition scores ( a = 0.01). However, although this monkey drank close to or more than his average 24 hr home

• = B a s e b n e - l n d a r k

= B c l s e h n e - c o n t i n u o u s f i lm o : F T - l m l n s c h e d u l e d fdrn d e h v e r y \

"--o

• A & • . . . . . . . . . . j ,~ , , , / / 1 2 3 L 5 ,6 7 8 9 10 16 17 18

Tes t Duys

3

23 2L

I. Water intake by the monkey Jonesy during daily 1 hour baseline and scheduled film delivery sessions.

A HENRY

A = Base,lne in dcrk = Base tme- it', Jght

!007 * : B ~ s e h r , e - scheduLed ~ght demver~'

4 o : F T - l m l n schedu!ed vtewm, g of sh'md ds m o r l k e / 80 i • = F T lmtn s c h e d u l e d v lew tng at shred]us monkey

Scar Fcice

' Hen ry '

%

• A ~ A Z~

2 ] z, 5 6 7 8 9 10 11 12 13 1/. 15 16 17

Test Drays

B JONESY

100

/o /

/ /

/ d

O O

-o7 50 '\

°- - . . .o/ /° ', ~ L O 'L

~ o..

20 ';,

. . . . . . . . / / . . . . . 11 12 13 1h 15 19 20 21 22 25 26 27 28 29 ~r" 31 t2

Test Days

FIG. 2. Water intake by the monkeys Henry and Jonesy during daily l hour baseline sessions or scheduled viewing of another monkey.

cage water intake during the second, third and fourth exper- imental hours of film viewing, water intake dropped during subsequent viewings. When scheduled film viewing was in- terrupted for a few days, as from days 10-16 and 18-23 in Fig. l, water intake rose briefly upon the first reviewing, but soon dropped again. Similar data were obtained for the mon- key " H e n r y , " but the third monkey "Scar Face , " failed to exhibit drinking above low baseline levels during experi- mental sessions.

Scheduled Viewing of Another Monkey

Figures 2A and 2B show water intake for the monkeys " H e n r y " and " Jonesy" during baseline and experimental

POLYDIPSIA AND V I S U A L DISPLAY SCHEDULES 381

conditions of schedule stimulus monkey viewing. During ex- perimental sessions both monkeys drank amounts of water approximately equivalent to their average 24 hour home cage water intake and well above the negligible water intake dur- ing any of the baseline conditions but " J o n e s y ' s " experi- mental session water intake was consistently greater when the stimulus monkey was "Scar Face" than when it was " H e n r y . " Mann-Whitney U tests showed that differences between baseline and experimental condition scores were significant (a=0.01) for both monkeys.

The third monkey, "Sca r Face , " failed to show drinking above low baseline levels during scheduled monkey viewing, just as he failed to do during scheduled film viewing.

When home cage isolation was ended both monkeys ' drinking during experimental sessions dropped to baseline levels within one session. When home cage isolation was re-established for the monkey " Jonesy" water intake during scheduled monkey viewing rose rapidly again.

DISCUSSION

The present results indicate that polydipsia may be in- duced in monkeys exposed to various visual display schedules. Previous experiments have demonstrated that a variety of behaviors may be generated by food delivery and other schedules, but with the exception of one study [16] polydipsia has always been induced by the use of food deliv- ery schedules to hungry animals.

Since polydipsia was induced in free feeding weight ani- mals and without a food delivery schedule the present exper- iment vitiates explanations of adjunctive polydipsia in terms of food associated or prandial drinking. As the schedules used here were non-contingent and water intake was minimal during baseline conditions, explanations of the polydipsia as superstitious behavior also seem untenable.

Although water intake during the experimental sessions

was higher than the animals 24 hr home cage consumption on non-experimental days and the drinking was distributed over the whole experimental hour, there is not enough data on the pattern of this distribution to claim that it is identical to post pellet drinking in the rat. However, since the drinking oc- curred in the presence of a schedule and was completely abolished without any transition period when the schedule was removed, it can be claimed that the drinking behavior reported here was scheduled induced.

The generality of schedule-induced drinking is demon- strated here in two ways. First , 2 out of the 3 animals devel- oped polydipsia during the presentation of visual stimuli. One of these animals, " Jonesy" had prior to this experiment developed polydipsia when body weight reduced and placed on various food delivery schedules. Second, the one mon- key, "Sca r Face , " who failed to become polydipsic during this experiment had also failed to demonstrate polydipsia in previous experiments involving food delivery schedules. Thus the mechanisms either facilitating or inhibiting the de- velopment of schedule-induced drinking in different subjects on food delivery schedules would seem to be similarly in- volved during the scheduled presentation of visual stimuli.

The data indicate that it is as important for an animal exposed to visual display schedules to be visually deprived in the home cage as for an animal placed on food delivery schedules to be food deprived.

The quality or saliency of the stimulus also seems to be important. Repetition of scheduled film delivery appeared to lead to habituation, and although scheduled viewing of a stimulus monkey was more effective in generating polydip- sia, the identity of the stimulus monkey appeared influential.

Although only three animals were tested the data pre- sented here suggest the greater generality and complexity of schedule-induced behaviors and show that schedule-induced polydipsia cannot be regarded as an artifact of food as- sociated drinking.

REFERENCES

I. Allen, J. D. and D. R. Kenshalo Jr. Schedule induced drinking as a function of interreinforcement interval in the rhesus mon- key. J. exp. Analysis behav. 26:257-267, 1976.

2. Butler, R. A. Curiosity in monkeys. Sci. Am. 190:70-75, 1954. 3. Clark, F. C. Some observations on the adventitious reinforce-

ment of drinking under food reinforcement. J. exp. Ana(vsis Behav. 5: 61--63, 1962.

4. Cook, P. and G. Singer. The effects of stimulus displacement on adjunctive behavior. Physiol. Behav. 16: 79-82, 1976.

5. DeWeese, J. Schedule-induced biting under fixed-interval schedules of food or electric-shock presentation. J. exp. Analysis. Behav. 27: 419-431, 1977.

6. Edington, E. S. Statistical inference from N= 1 experiments. J. Psychol. 65: 195-199, 1967.

7. Falk, J. L. Production of polydipsia in normal rats by an inter- mittent food schedule. Science 133: 195-196, 1961.

8. Harlow, F. and M. K. Harlow. Social deprivation in monkeys. Sci. Am. 107: 136--146, 1962.

9. Kachanoff, R., R. Leveille, J. P. McLelland and M. J. Wayner. Schedule induced behavior in humans. Physiol. Behav. 11: 395-398, 1973.

10. Klinger, A., R. Kachanoff, D. P. Dastoor, A. Worenklein, S. Charlton, E. Gutbrodt and H. F. MfJller. A psychogeriatric assessment program. III Clinical and experimental psychologic aspects. J. Am. Geriat. Soc. 24: 17-24, 1976.

11. Palfai, T., C. L. lgutscher and J. P. Symons. Schedule-induced polydipsia in the mouse. Physiol. Behav. 6: 461-462, 1971.

12. Porter, J. H. and D. R. Kenshalo Jr. Schedule-induced drinking following omission of reinforcement in the rhesus monkey. Physiol. Behav. 12: 1075-1077, 1974.

13. Schuster, C. R. and J. H. Woods. Schedule-induced polydipsia in the rhesus monkey. Psychol. Rep. 19: 823--828, 1966.

14. Shanab, M. and J. I. Peterson. Polydipsia in the pigeon. Psychon. Sci. 15: 51-52, 1969.

15. Siegel, S. Nonparametric Statistics. New York: McGraw-Hill, 1956.

16. Singer, G., M. J. Wayner, J. Stein, K. Cimino and K. King. Adjunctive behavior induced by wheel running. Physiol. Behav. 12: 493-495, 1974.

17. Skinner, B. F. and W. H. Morse. Concurrent activity under fixed-interval reinforcement. J. comp. physiol. Psychol. 50: 279-281, 1957.

18. Wallace, M. and G. Singer. Schedule induced behavior: A re- view of its generality, determinants and pharmacological data. Pharmac. Biochem. Behav. 5: 483-490, 1976.

19. Wallace, M. and G. Singer. Adjunctive behavior and smoking induced by a maze solving schedule in humans. Physiol. Behav. 17: 849-852, 1976.

20. Wallace, M., G. Singer, M. J. Wayner and P. Cook. Adjunctive behavior in humans during game playing. Physiol. Behav. 14: 651-654, 1975.