ONTOGENY OF RESPONSE TO HUMANS IN HANDLED AND NONHANDLED FEMALE DOMESTIC CHICKS

Regular handling is widely known to reduce the domestic chick's fear of human beings, but the ontogeny of this phenomenon is less well understood. Therefore, the present study compared the responses of handled and non-handled female chicks to a visible experimenter at one of five ages (2, 3, 4, 6 or 9 days). Fear of humans was functionally measured here in terms of the chicks' approach/avoidance tendencies towards a visible experimenter. Handling, which consisted of picking the chick up and stroking it gently for 30 s, was applied twice on test days and three times on non-test days. Thus, handled chicks tested al the above ages had received either 3, 5, 7, 12 or 20 handling episodes. Each chick was tested individually and once only. As expected, avoidance of the experimenter was considerably reduced by the handling regime. Significant divergence between the responses of handled and non-handled chicks first became apparent in 4-day-old birds and the magnitude of this dichotomy then increased progressively. Although this study was not designed specifically to dissociate handling and maturational effects, the observed treatment effects apparently reflected two distinct processes. Firstly, avoidance of the experimenter increased with age in previously untested non-handled chicks. Secondly, despite increasing age, the cumulative experience of regular handling was accompanied by a tendency towards the progressive reduction of such avoidance.