Journal of Comparative and Physiological Psychology 1976, Vol. 90, No. 9, 870-876
Habituation and Tonic Immobility in Domestic Chickens Richard F. Nash Marquette University
Gordon G. Gallup, Jr. State University of New York at Albany
The habituation of tonic immobility in chickens was examined in six studies. It was shown that repeated elicitation of immobility, and not just handling, was responsible for reduced response durations after multiple exposures to manual restraint. Habituation was a function of the number of stimulus presentations and, in addition, proved surprisingly durable, with diminished reactions lasting at least 2.5 mo. Strain differences were found in the number of trials required to reach a criteria of habituation, and habituation proceeded faster when immobility termination was self-paced as opposed to experimenter induced. Also, massed trials produced robust sensitization effects rather than diminished responsiveness.
Habituation refers to a relatively permanent, stimulus-specific decrement in response strength that occurs as a consequence of repeated response elicitation. Such changes have been considered the most elementary form of behavioral modification (Thorpe, 1956). Current theories of habituation are varied, including Sokolov's (1963) stimulusmodel comparator theory, Stein's (1966) analysis in terms of classical conditioning, Ratner's (1970) elicitation and interference theory, and the dual-process theory of Groves and Thompson (1970). Many different organisms and stimulusresponse relations have been used to study habituation. Some specific examples include the startle response to a loud noise in rats (Korn & Moyer, 1966), the mobbing response to a predator in chaffinches (Hinde, 1954), the wiping response to tactual stimulation in frogs (Kimble & Ray, 1965), and the immobility response to manual restraint in chickens (Ratner & Thompson, 1960; Prestrude & Crawford, Note 1). Tonic immobility (TI) is an unlearned response triggered by physical restraint (Gallup, 1974a) and characterized by a catatonic-like state of reduced responsiveness, which may last from a few minutes to over several hours. The reaction has proven unusually sensitive to manipulations designed The authors would like to thank Sara Garrison, Lou E. Hicks, and J. Frank Popplewell for help in data collection. Requests for reprints should be sent to R. F. Nash, Department of Psychology, Marquette University, Milwaukee, Wisconsin 53233.
to affect changes in fear (Gallup, 1974a). While it is known that TI does habituate after repeated elicitation in many species (apparent exceptions include rhesus monkeys: Foley, 1938; iguanas: Prestrude & Crawford, 1970; and frogs :Boice & Williams, 1971), there has been relatively little attention to habituation processes and tonic immobility. On the other hand, many investigators in this area use habituation procedures for methodological and control purposes (Gallup, Nash, & Wagner, 1971). The present study was designed to investigate some of the possible parameters of this process in chickens. EXPERIMENT 1 Repeated handling is a potent immobility antagonist (e.g., Oilman, Marcuse, & Moore, 1950); therefore, one could argue that the response reduction that appears to occur as a result of repeated testing might be a reflection of handling, and not response elicitation. The first experiment was conducted to determine whether reduced duration of TI after repeated testing was merely due to handling or to actual response elicitation. Method Subjects. The subjects were 34 straight run, Production Red chicks, obtained from a local hatchery at 2 days of age. The birds were housed in commercial brooders and given continuous access to Purina chick chow (Growena) and water. The photoperiod in effect during rearing was 14 hr of artificial light per day. Apparatus. Training and testing procedures were carried out in a three-sided (.61 X .61 X 870
HABITUATION AND IMMOBILITY .50 m) wooden induction box used to eliminate extraneous visual cues. Duration of immobility was monitored with a Hunter Klockounter (Model 120C). Procedure. At 2 wk of age the birds were randomly divided into two groups (handled group and habituated group) of 17 birds each. Chicks in the habituated group were given four consecutive days of testing, which consisted of manually restraining a bird on its left side for 15 sec in the induction box. The duration of each resulting immobility episode was terminated after about 15 sec by gentle prodding, and each bird was given five inductions per day, with a 15-sec intertrial interval (ITI). During testing, the experimenter sat quietly on a chair about .9 m away and avoided making direct eye contact with the subject. Large plywood boxes, provided with ventilation holes and food, were used to transport subjects and as pre- and posttest holding boxes located outside the testing room. Birds in the handled group received 2 min of gentle handling, petting, and stroking by the experimenter each day for 4 days but were never subject to explicit restraint. The 2-min handling regimen was used to approximate the amount of actual experimenter-subject contact time for each habituated bird per day. Birds from both groups were run alternately each day. On Day 5, subjects in both groups were tested individually by being manually restrained on their left side. The duration of immobility was recorded from the time restraint ended until the bird rose to its feet. If a chick did not show immobility after the first induction, it was given repeated 15-sec inductions, with a 15-sec ITI, until immobility obtained or until five inductions had been administered, in which latter case a duration of zero was recorded. Results Habituated subjects displayed much shorter immobility times (X = 21.18 sec, SD = 20.73 sec) compared with handled subjects (X = 124.98 sec, SD = 123.03 sec) and required many more inductions (X = 3.35, -SD = 1.58) than did handled birds (X = 1.47, SD = 1.07). A between-groups analyis of variance, computed on a logio (X + 1) transformation of the duration data, revealed a significant groups effect, F(l, 32) = 11.90, p < .005. A between-groups analysis of variance of the number of inductions needed to elicit immobility also showed a significant groups effect, F(i, 32) = 16.58,
p < .001.
tion of tonic immobility and susceptibility to the reaction. Since it is known that up to a point, the more stimulus presentations, the greater the degree of habituation (Denny & Ratner, 1970, chap. 10), the second experiment was designed to explore this relationship. Method Subjects. The subjects were 85 straight run, Production Red chicks, housed and maintained as in Experiment 1. Procedure. At 15 days of age the birds were randomly divided into five groups of 17 subjects each. The following day (Day 1) birds in Group 1 were manually restrained once in the induction box, and the duration of immobility was recorded. The birds in the remaining four groups were given habituation training (five trials per day), with the procedure used in the first experiment, for 1, 2, 3, or 4 days prior to testing. The procedure was such that separate groups of birds were tested for duration of TI after 0,1, 2, 3, or 4 days of habituation training. Results Figure 1 shows that the mean duration of immobility decreases very rapidly and then levels off with continued testing. A betweengroups analysis of variance, computed on a logio (X + 1) transformation of the duration data, showed a significant effect of number of days of habituation, F(4, 80) = 11.77, p
Habituation and Tonic Immobility in Domestic Chickens Richard F. Nash Marquette University
Gordon G. Gallup, Jr. State University of New York at Albany
The habituation of tonic immobility in chickens was examined in six studies. It was shown that repeated elicitation of immobility, and not just handling, was responsible for reduced response durations after multiple exposures to manual restraint. Habituation was a function of the number of stimulus presentations and, in addition, proved surprisingly durable, with diminished reactions lasting at least 2.5 mo. Strain differences were found in the number of trials required to reach a criteria of habituation, and habituation proceeded faster when immobility termination was self-paced as opposed to experimenter induced. Also, massed trials produced robust sensitization effects rather than diminished responsiveness.
Habituation refers to a relatively permanent, stimulus-specific decrement in response strength that occurs as a consequence of repeated response elicitation. Such changes have been considered the most elementary form of behavioral modification (Thorpe, 1956). Current theories of habituation are varied, including Sokolov's (1963) stimulusmodel comparator theory, Stein's (1966) analysis in terms of classical conditioning, Ratner's (1970) elicitation and interference theory, and the dual-process theory of Groves and Thompson (1970). Many different organisms and stimulusresponse relations have been used to study habituation. Some specific examples include the startle response to a loud noise in rats (Korn & Moyer, 1966), the mobbing response to a predator in chaffinches (Hinde, 1954), the wiping response to tactual stimulation in frogs (Kimble & Ray, 1965), and the immobility response to manual restraint in chickens (Ratner & Thompson, 1960; Prestrude & Crawford, Note 1). Tonic immobility (TI) is an unlearned response triggered by physical restraint (Gallup, 1974a) and characterized by a catatonic-like state of reduced responsiveness, which may last from a few minutes to over several hours. The reaction has proven unusually sensitive to manipulations designed The authors would like to thank Sara Garrison, Lou E. Hicks, and J. Frank Popplewell for help in data collection. Requests for reprints should be sent to R. F. Nash, Department of Psychology, Marquette University, Milwaukee, Wisconsin 53233.
to affect changes in fear (Gallup, 1974a). While it is known that TI does habituate after repeated elicitation in many species (apparent exceptions include rhesus monkeys: Foley, 1938; iguanas: Prestrude & Crawford, 1970; and frogs :Boice & Williams, 1971), there has been relatively little attention to habituation processes and tonic immobility. On the other hand, many investigators in this area use habituation procedures for methodological and control purposes (Gallup, Nash, & Wagner, 1971). The present study was designed to investigate some of the possible parameters of this process in chickens. EXPERIMENT 1 Repeated handling is a potent immobility antagonist (e.g., Oilman, Marcuse, & Moore, 1950); therefore, one could argue that the response reduction that appears to occur as a result of repeated testing might be a reflection of handling, and not response elicitation. The first experiment was conducted to determine whether reduced duration of TI after repeated testing was merely due to handling or to actual response elicitation. Method Subjects. The subjects were 34 straight run, Production Red chicks, obtained from a local hatchery at 2 days of age. The birds were housed in commercial brooders and given continuous access to Purina chick chow (Growena) and water. The photoperiod in effect during rearing was 14 hr of artificial light per day. Apparatus. Training and testing procedures were carried out in a three-sided (.61 X .61 X 870
HABITUATION AND IMMOBILITY .50 m) wooden induction box used to eliminate extraneous visual cues. Duration of immobility was monitored with a Hunter Klockounter (Model 120C). Procedure. At 2 wk of age the birds were randomly divided into two groups (handled group and habituated group) of 17 birds each. Chicks in the habituated group were given four consecutive days of testing, which consisted of manually restraining a bird on its left side for 15 sec in the induction box. The duration of each resulting immobility episode was terminated after about 15 sec by gentle prodding, and each bird was given five inductions per day, with a 15-sec intertrial interval (ITI). During testing, the experimenter sat quietly on a chair about .9 m away and avoided making direct eye contact with the subject. Large plywood boxes, provided with ventilation holes and food, were used to transport subjects and as pre- and posttest holding boxes located outside the testing room. Birds in the handled group received 2 min of gentle handling, petting, and stroking by the experimenter each day for 4 days but were never subject to explicit restraint. The 2-min handling regimen was used to approximate the amount of actual experimenter-subject contact time for each habituated bird per day. Birds from both groups were run alternately each day. On Day 5, subjects in both groups were tested individually by being manually restrained on their left side. The duration of immobility was recorded from the time restraint ended until the bird rose to its feet. If a chick did not show immobility after the first induction, it was given repeated 15-sec inductions, with a 15-sec ITI, until immobility obtained or until five inductions had been administered, in which latter case a duration of zero was recorded. Results Habituated subjects displayed much shorter immobility times (X = 21.18 sec, SD = 20.73 sec) compared with handled subjects (X = 124.98 sec, SD = 123.03 sec) and required many more inductions (X = 3.35, -SD = 1.58) than did handled birds (X = 1.47, SD = 1.07). A between-groups analyis of variance, computed on a logio (X + 1) transformation of the duration data, revealed a significant groups effect, F(l, 32) = 11.90, p < .005. A between-groups analysis of variance of the number of inductions needed to elicit immobility also showed a significant groups effect, F(i, 32) = 16.58,
p < .001.
tion of tonic immobility and susceptibility to the reaction. Since it is known that up to a point, the more stimulus presentations, the greater the degree of habituation (Denny & Ratner, 1970, chap. 10), the second experiment was designed to explore this relationship. Method Subjects. The subjects were 85 straight run, Production Red chicks, housed and maintained as in Experiment 1. Procedure. At 15 days of age the birds were randomly divided into five groups of 17 subjects each. The following day (Day 1) birds in Group 1 were manually restrained once in the induction box, and the duration of immobility was recorded. The birds in the remaining four groups were given habituation training (five trials per day), with the procedure used in the first experiment, for 1, 2, 3, or 4 days prior to testing. The procedure was such that separate groups of birds were tested for duration of TI after 0,1, 2, 3, or 4 days of habituation training. Results Figure 1 shows that the mean duration of immobility decreases very rapidly and then levels off with continued testing. A betweengroups analysis of variance, computed on a logio (X + 1) transformation of the duration data, showed a significant effect of number of days of habituation, F(4, 80) = 11.77, p
