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Hunger and thirst in shock-induced aggression
BEHAVIORAL BIOLOGY,8, 433-437 (1973), Abstract No. 1-160
H u n g e r a n d T h i r s t in S h o c k - I n d u c e d Aggression
THOMAS L. CREER
Children's Asthma Research Institute and Hospital Denver, Colorado 80204
The effects of food and water deprivation were studied in rats that, at the outset of the experiment, exhibited either low or high rates of fighting in response to foot shock. Hunger and thirst were found not to affect the mean rates of fighting in Ss whose initial frequency of fighting to footshock was high. While food deprivation also did not affect the frequency of fighting in low aggression Ss, water deprivation resulted in a marked increase in the fighting observed between members of this group.
The interaction of hunger and thirst with behavior has previously been investigated (Rosenzweig, 1962; Teitelbaum, 1964). An area of recent interest has been how hunger and thirst affect aggression. Cahoon, Crosby, Dunn, Herrin, Hill, and McGinniss (1971), for example, found that not only did food deprivation plus shock induce a higher rate of biting than shock alone, but that the number of such responses varied positively with the amount of deprivation. Water deprivation plus shock, on the other hand, induced fewer biting and pulling responses than shock alone (Hamby and Cahoon, 1971). The purpose of the present study was to determine how food and water deprivation interact with shock-induced fighting in paired rats. An additional aim was to compare the effect of the above variables on two subgroups of Ss: Rats that consistently fight at a high rate in response to foot shock, and rats that regularly exhibit a low rate of fighting in response to the same stimulus. METHOD
Sub/ects Twenty male experimentally naive, 90-day-old Sprague-Dawley rats were initially paired on the basis of weight. Throughout the course of the study, the animals were housed individually in separate cages.
Apparatus and Procedure A detailed description of the apparatus used in this study is found in 433 Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.
434
CREER
Creer and Powell (1971b). It essentially consisted of a Grason-Stadler model E3125 rat box and a modular programming system. Fighting responses were defined in a manner described by Ulrich and Azrin (1962). Two Es independently marked separate sheets of paper to record the striking movements that occurred between rats, standing upright and facing one another, with each shock presentation. Greater than 95% agreement was obtained between the two Es in registering shock-elicited fighting in this study. Azrin, Ulrich, Hutchinson, and Norman (1964) reported that 2-mA shocks of a duration of 0.5 sec were optimal for inducing fighting in paired rats. These parameters were used in the present study. The shock was presented at a frequency of 20 shocks per minute. The Ss received 100 shocks daily for 41 consecutive days. During the first session, the animals were observed for a period before shock was presented to determine if any spontaneous fighting took place between Ss. None of the animals exhibited this behavior. Initially, the Ss were placed in the experimental chamber daily until the rate of fighting between each pair stabilized. The criterion for stability was met when, during seven consecutive sessions, fighting frequencies remained within a range of 10 responses. This procedure insured that any subsequent changes in the Ss' rates of fighting would be due to experimental manipulations and did not represent the alterations in fighting frequencies noted during initial sessions in other studies of shock-induced aggression (Creer and Powell, 1971a,b; Powell and Creer, 1969). The study consisted of five consecutive phases: Baseline. The seven sessions in which the rates of fighting remained within a range of 10 responses constituted the baseline measure. This criterion was achieved in all Ss in from 10-14 sessions. Of the 10 pairs of Ss, six were observed to fight at high frequencies in that aggression occurred on at least 90% of the trials. The remaining four pairs, on the other hand, fought at low rates in that fighting was witnessed during less than 10% of the trials. Food deprivation. After stable baselines were obtained, the Ss were totally deprived of food for 7 consecutive days. Water was freely available, however. Recovery. After the 7 days of food deprivation, the Ss were provided with free access to both food and water over a 10-day period. Body weights were found to have recovered prefood deprivation levels at the end of this phase. Water deprivation. The Ss were deprived of water for 7 consecutive days, but were allowed free access to food. Recovery. The animals were provided with free access to both food and water for a second 10-day recovery period. At the end of this time, body weights had regained prewater deprivation levels. RESULTS AND DISCUSSION The mean rates of fighting observed' across conditions by the Ss in the
HUNGER AND THIRST IN SHOCK-INDUCEDAGGRESSION
435
low- and high-frequency fighting groups are shown in Fig. 1. As indicated, the high-frequency fighters fought at high rates during each condition of the experiment. During the latter stage of the study in particular, there were root:, BASELINE 100 i °,.
90
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EREOUENCY FREQUENCY GROUP j
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SESSIONS
Fig. 1. The mean rates of aggression observed in the two groups across experimental conditions. sessions in which the animals fought 100% of the time to the shock. A repeated measures analysis of variance revealed no significant differences in the rates of the high-frequency fighters across sessions (F(4,20)=1.58; P > 0.10). Such behavior emphasizes the stability of shock-induced aggression over a large number of sessions. Little change in the mean rates of fighting was witnessed with the rats categorized as low-frequency fighters until water was withdrawn. Under these conditions, the mean fighting frequency exhibited by these Ss steadily increased. This rate subsequently decreased when water again became available, but in comparison to the frequency of fighting noted in the first recovery period, the mean rate of this group remained slightly elevated. A repeated-measures analysis of variance on these data indicated that the differences in the rates of fighting observed across sessions were highly significant (F(4,12)=56.56; P < 0 . 0 0 1 ) . Further analyses with the Newman-Keuls procedure for making between-condition comparisons (Weiner, 1962) indicated that the last two conditions (water deprivation and recovery) were significantly different ( P < 0.01) from the remaining conditions. This suggests that shock, in and of itself, lacked the aversiveness required to induce aggression between the pairs in this group, unless coupled with water deprivation. Whether or not water deprivation had a similar effect with the
436
CREER
high-fighting group cannot be determined from the present results. The high rates of responding obtained over sessions impose a ceiling effect that obscures this point. Further research utilizing shock parameters that lead to lower baseline responding is required to clarify this question. At the same time, additional experimentation should be conducted to determine why water deprivation but not food deprivation affected shock-induced fighting with the low-frequency fighters. A place to begin would be to investigate the correlated nature of eating and drinking (i.e., the fact that rats deprived of water will not eat) and its relationship to shock-induced aggression. Cahoon and his colleagues previously found that food deprivation increased (Cahoon et aL, 1971), but water deprivation decreased (Hamby and Cahoon, 1971) shock-induced biting and pulling. In contrast, the present study indicated that water deprivation increased the frequency of rats previously characterized as low-frequency fighters. The most likely explanation for the disparity of results is that Cahoon and his co-workers and the present E investigated different behavior phenomena. Thus, the two previous studies examined the attack of a restrained animal upon an inanimate target, whereas the present study examined fighting between pairs of animals in a free-responding environment. Other procedural dissimilarities between studies include (a) locus of shock presentation, (b) duration of food and water deprivation, and (c) previous experiences with shock and with shock-induced aggression before being tested in the deprivation conditions. In view of the large number of procedural differences between studies, additional experiments will have to be carried out before the mechanism or mechanisms by which food or water deprivation influence aggressive behavior can be specified.
REFERENCES Azfin, N.H., Ulrich, R.E., Hutchinson, R.R., and Norman, D.G. (1964). Effects of shock duration on shock-induced fighting. £ Exp. Anal Behav. 7, 9-11. Cahoon, D.D., Crosby, R.M., Dunn, S., Herrin, M.S., Hill, C.C., and MeGinniss, M. (1971). The effect of food deprivation on shock-elicited aggression in rats. Psychon. ScL 22, 43-44. Creer, T.L., and Powell, D.A., (1971). Effects of age and housing conditions on shock-induced aggression. Psychon, Sci. 22, 259-261. (a) Creer, T.L., and Powell, D.A., (1971). Effect of repeated shock presentations and different stimulus intensities on shock-induced aggression. Psychon. Sci. 24, 133-134. (b) Hamby, W., and Cahoon, D.D. (1971). The effect of water deprivation upon shock-induced aggressionin the white rat. Psychon. Sc£ 23, 52. PoweU, D.A., and Creel T.L. (1969). Interaction of developmental and environmental variables in shock-elicitedaggression. £ Comp. PhysioL Psychol. 69, 219-225. Rosenzweig, M.R. (1962). The mechanisms of hunger and thirst. In L. Postman (Ed.), "Psychology in the Making," New York: Knopf. Teitelbaum, P. (1964). Appetite.. In "Psychology: A Behavioral Reinterpretation," Philadelphia: American Philosophical Society.
HUNGER AND THIRST IN SHOCK-INDUCEDAGGRESSION
437
Ulrich, R.E., and Azrin, N.H. (1962). Reflexive flighting in response to aversive stimuli. J. Exp. Anal. Behav. 5, 511-520. Winer, B.J. (1962). "Statistical Principles in Experimental Design," New York: McGraw-Hill.
H u n g e r a n d T h i r s t in S h o c k - I n d u c e d Aggression
THOMAS L. CREER
Children's Asthma Research Institute and Hospital Denver, Colorado 80204
The effects of food and water deprivation were studied in rats that, at the outset of the experiment, exhibited either low or high rates of fighting in response to foot shock. Hunger and thirst were found not to affect the mean rates of fighting in Ss whose initial frequency of fighting to footshock was high. While food deprivation also did not affect the frequency of fighting in low aggression Ss, water deprivation resulted in a marked increase in the fighting observed between members of this group.
The interaction of hunger and thirst with behavior has previously been investigated (Rosenzweig, 1962; Teitelbaum, 1964). An area of recent interest has been how hunger and thirst affect aggression. Cahoon, Crosby, Dunn, Herrin, Hill, and McGinniss (1971), for example, found that not only did food deprivation plus shock induce a higher rate of biting than shock alone, but that the number of such responses varied positively with the amount of deprivation. Water deprivation plus shock, on the other hand, induced fewer biting and pulling responses than shock alone (Hamby and Cahoon, 1971). The purpose of the present study was to determine how food and water deprivation interact with shock-induced fighting in paired rats. An additional aim was to compare the effect of the above variables on two subgroups of Ss: Rats that consistently fight at a high rate in response to foot shock, and rats that regularly exhibit a low rate of fighting in response to the same stimulus. METHOD
Sub/ects Twenty male experimentally naive, 90-day-old Sprague-Dawley rats were initially paired on the basis of weight. Throughout the course of the study, the animals were housed individually in separate cages.
Apparatus and Procedure A detailed description of the apparatus used in this study is found in 433 Copyright © 1973 by Academic Press, Inc. All rights of reproduction in any form reserved.
434
CREER
Creer and Powell (1971b). It essentially consisted of a Grason-Stadler model E3125 rat box and a modular programming system. Fighting responses were defined in a manner described by Ulrich and Azrin (1962). Two Es independently marked separate sheets of paper to record the striking movements that occurred between rats, standing upright and facing one another, with each shock presentation. Greater than 95% agreement was obtained between the two Es in registering shock-elicited fighting in this study. Azrin, Ulrich, Hutchinson, and Norman (1964) reported that 2-mA shocks of a duration of 0.5 sec were optimal for inducing fighting in paired rats. These parameters were used in the present study. The shock was presented at a frequency of 20 shocks per minute. The Ss received 100 shocks daily for 41 consecutive days. During the first session, the animals were observed for a period before shock was presented to determine if any spontaneous fighting took place between Ss. None of the animals exhibited this behavior. Initially, the Ss were placed in the experimental chamber daily until the rate of fighting between each pair stabilized. The criterion for stability was met when, during seven consecutive sessions, fighting frequencies remained within a range of 10 responses. This procedure insured that any subsequent changes in the Ss' rates of fighting would be due to experimental manipulations and did not represent the alterations in fighting frequencies noted during initial sessions in other studies of shock-induced aggression (Creer and Powell, 1971a,b; Powell and Creer, 1969). The study consisted of five consecutive phases: Baseline. The seven sessions in which the rates of fighting remained within a range of 10 responses constituted the baseline measure. This criterion was achieved in all Ss in from 10-14 sessions. Of the 10 pairs of Ss, six were observed to fight at high frequencies in that aggression occurred on at least 90% of the trials. The remaining four pairs, on the other hand, fought at low rates in that fighting was witnessed during less than 10% of the trials. Food deprivation. After stable baselines were obtained, the Ss were totally deprived of food for 7 consecutive days. Water was freely available, however. Recovery. After the 7 days of food deprivation, the Ss were provided with free access to both food and water over a 10-day period. Body weights were found to have recovered prefood deprivation levels at the end of this phase. Water deprivation. The Ss were deprived of water for 7 consecutive days, but were allowed free access to food. Recovery. The animals were provided with free access to both food and water for a second 10-day recovery period. At the end of this time, body weights had regained prewater deprivation levels. RESULTS AND DISCUSSION The mean rates of fighting observed' across conditions by the Ss in the
HUNGER AND THIRST IN SHOCK-INDUCEDAGGRESSION
435
low- and high-frequency fighting groups are shown in Fig. 1. As indicated, the high-frequency fighters fought at high rates during each condition of the experiment. During the latter stage of the study in particular, there were root:, BASELINE 100 i °,.
90
/''*/°-"
',
:
DEPRIVATION '; , , e~ • , , /"-'-
RECOVERY •
\..-',./
• • • • • . . . . . . .
•
e/
•
'.
WA~ER
', DEPRIVATION ', RECOVERY , J i ir~e~e , o~e~e-e~°~e-e~e~e i o-o~o~o I
*'"
8O
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EREOUENCY FREQUENCY GROUP j
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o /o'
~°~ x ° 5
"°~
r 10
'f 15
~ 20
'i 25
'
30
3
'5
'--
40
SESSIONS
Fig. 1. The mean rates of aggression observed in the two groups across experimental conditions. sessions in which the animals fought 100% of the time to the shock. A repeated measures analysis of variance revealed no significant differences in the rates of the high-frequency fighters across sessions (F(4,20)=1.58; P > 0.10). Such behavior emphasizes the stability of shock-induced aggression over a large number of sessions. Little change in the mean rates of fighting was witnessed with the rats categorized as low-frequency fighters until water was withdrawn. Under these conditions, the mean fighting frequency exhibited by these Ss steadily increased. This rate subsequently decreased when water again became available, but in comparison to the frequency of fighting noted in the first recovery period, the mean rate of this group remained slightly elevated. A repeated-measures analysis of variance on these data indicated that the differences in the rates of fighting observed across sessions were highly significant (F(4,12)=56.56; P < 0 . 0 0 1 ) . Further analyses with the Newman-Keuls procedure for making between-condition comparisons (Weiner, 1962) indicated that the last two conditions (water deprivation and recovery) were significantly different ( P < 0.01) from the remaining conditions. This suggests that shock, in and of itself, lacked the aversiveness required to induce aggression between the pairs in this group, unless coupled with water deprivation. Whether or not water deprivation had a similar effect with the
436
CREER
high-fighting group cannot be determined from the present results. The high rates of responding obtained over sessions impose a ceiling effect that obscures this point. Further research utilizing shock parameters that lead to lower baseline responding is required to clarify this question. At the same time, additional experimentation should be conducted to determine why water deprivation but not food deprivation affected shock-induced fighting with the low-frequency fighters. A place to begin would be to investigate the correlated nature of eating and drinking (i.e., the fact that rats deprived of water will not eat) and its relationship to shock-induced aggression. Cahoon and his colleagues previously found that food deprivation increased (Cahoon et aL, 1971), but water deprivation decreased (Hamby and Cahoon, 1971) shock-induced biting and pulling. In contrast, the present study indicated that water deprivation increased the frequency of rats previously characterized as low-frequency fighters. The most likely explanation for the disparity of results is that Cahoon and his co-workers and the present E investigated different behavior phenomena. Thus, the two previous studies examined the attack of a restrained animal upon an inanimate target, whereas the present study examined fighting between pairs of animals in a free-responding environment. Other procedural dissimilarities between studies include (a) locus of shock presentation, (b) duration of food and water deprivation, and (c) previous experiences with shock and with shock-induced aggression before being tested in the deprivation conditions. In view of the large number of procedural differences between studies, additional experiments will have to be carried out before the mechanism or mechanisms by which food or water deprivation influence aggressive behavior can be specified.
REFERENCES Azfin, N.H., Ulrich, R.E., Hutchinson, R.R., and Norman, D.G. (1964). Effects of shock duration on shock-induced fighting. £ Exp. Anal Behav. 7, 9-11. Cahoon, D.D., Crosby, R.M., Dunn, S., Herrin, M.S., Hill, C.C., and MeGinniss, M. (1971). The effect of food deprivation on shock-elicited aggression in rats. Psychon. ScL 22, 43-44. Creer, T.L., and Powell, D.A., (1971). Effects of age and housing conditions on shock-induced aggression. Psychon, Sci. 22, 259-261. (a) Creer, T.L., and Powell, D.A., (1971). Effect of repeated shock presentations and different stimulus intensities on shock-induced aggression. Psychon. Sci. 24, 133-134. (b) Hamby, W., and Cahoon, D.D. (1971). The effect of water deprivation upon shock-induced aggressionin the white rat. Psychon. Sc£ 23, 52. PoweU, D.A., and Creel T.L. (1969). Interaction of developmental and environmental variables in shock-elicitedaggression. £ Comp. PhysioL Psychol. 69, 219-225. Rosenzweig, M.R. (1962). The mechanisms of hunger and thirst. In L. Postman (Ed.), "Psychology in the Making," New York: Knopf. Teitelbaum, P. (1964). Appetite.. In "Psychology: A Behavioral Reinterpretation," Philadelphia: American Philosophical Society.
HUNGER AND THIRST IN SHOCK-INDUCEDAGGRESSION
437
Ulrich, R.E., and Azrin, N.H. (1962). Reflexive flighting in response to aversive stimuli. J. Exp. Anal. Behav. 5, 511-520. Winer, B.J. (1962). "Statistical Principles in Experimental Design," New York: McGraw-Hill.