PASSIVE SOCIALIZATION TO HUMANS - EFFECTS ON TONIC IMMOBILITY IN CHICKENS (GALLUS-GALLUS)

Chicks whose primary source of visual stimulation during rearing was in the form of human caretakers showed significantly shorter durations of tonic immobility. Birds with only human visual exposure were also more likely to behave in affiliative ways toward the experimenter than were birds from the other rearing groups. Birds reared in a similar manner but tested for tonic immobility in the absence of the experimenter failed to show an effect. The results are discussed in terms of the phylogenetic generality of ontogenetic-dependent reactivity to humans, and the possibility that the ecological validity of experimental studies in which animals are reared in isolation from conspecifics, or otherwise become socialized to humans, may be compromised.