The Varieties of Social Stimulation in the Feeding Behaviour of Domestic Chicks

[1. Three experiments were reported on the problem of identifying the nature of the social stimulus in the feeding behaviour of domestic chicks. 2. The first experiment investigated the effects of restriction of subject and of the companion by a clear plastic barrier, and of the level of food deprivation of the companion, in a 2 × 2 factorial design. The results showed the companion's food deprivation to be important but not restriction. This result encouraged further use of the restricted condition in investigation of stimulus variables. 3. The second experiment showed a nonfeeding (but otherwise active) companion to have a facilitative effect upon feeding that is intermediate in magnitude between effects of no companion and of one who is feeding. 4. The third experiment partially replicated the result of the second and showed that a dead (merely present) companion in a sleeping posture had no effect upon the feeding of the subject. 5. The fourth experiment showed that nonfeeding companions do peck, but when the amount of pecking was reduced by experimental means, an accompanying reduction did not occur in the subject's feeding behaviour. Subjects with nonactive companions ate less than subjects with active, but not pecking, companions. 6. It was concluded that the mere presence of a companion has no stimulus properties relevant to feeding. The relevant stimuli appeared to fall into at least three categories: (a) physical contact with companion-which is probably only of very minor importance; (b) nonfeeding activity of companion; and (c) feeding activity of companion., 1. Three experiments were reported on the problem of identifying the nature of the social stimulus in the feeding behaviour of domestic chicks. 2. The first experiment investigated the effects of restriction of subject and of the companion by a clear plastic barrier, and of the level of food deprivation of the companion, in a 2 × 2 factorial design. The results showed the companion's food deprivation to be important but not restriction. This result encouraged further use of the restricted condition in investigation of stimulus variables. 3. The second experiment showed a nonfeeding (but otherwise active) companion to have a facilitative effect upon feeding that is intermediate in magnitude between effects of no companion and of one who is feeding. 4. The third experiment partially replicated the result of the second and showed that a dead (merely present) companion in a sleeping posture had no effect upon the feeding of the subject. 5. The fourth experiment showed that nonfeeding companions do peck, but when the amount of pecking was reduced by experimental means, an accompanying reduction did not occur in the subject's feeding behaviour. Subjects with nonactive companions ate less than subjects with active, but not pecking, companions. 6. It was concluded that the mere presence of a companion has no stimulus properties relevant to feeding. The relevant stimuli appeared to fall into at least three categories: (a) physical contact with companion-which is probably only of very minor importance; (b) nonfeeding activity of companion; and (c) feeding activity of companion.]