Effects of prior video stimulation on open-field behaviour in domestic chicks

Abstract

Two experiments examined the effects of regular video stimulation on open-field behaviour in domestic chicks tested in the presence (Experiment 1) or absence (Experiment 2) of the familiar video image. In Experiment 1, socially housed chicks were either exposed daily from 2 to 8 days of age to the video image of a computer screensaver (SS) in their home cage, or not (N). At 9, 10 or 11 days of age each chick was tested individually in a square, black open field with either the SS video or just a sheet of black card (control, BC) visible through a wire-mesh window in one of the walls. SS chicks approached the familiar video image sooner and spent longer near it than N ones. These findings are consistent with earlier reports that familiar SS images were attractive to domestic chicks in a two-choice runway test and they show that this phenomenon generalizes to include a one-choice open-field situation. Our observations that SS chicks also walked significantly more and tended to vocalize sooner than N ones regardless of the test situation suggested that previous video stimulation may have reduced their fear of this novel environment. This was tested in Experiment 2 in which group-housed chicks were either exposed for 40 min per day from 2 to 8 days of age to a composite video (CV) image of five screensavers in their home cage, or not (control, C). All chicks were then tested individually in a uniformly black open field with no video present. Freezing was shown by fewer CV than C chicks. The CV chicks also showed shorter durations of freezing, they entered more areas of the open field and tended to vocalize sooner than those from the C group. These results support the suggestion that regular exposure to a complex CV image during the first week of life decreased chicks' fear when they were subsequently placed in an unfamiliar environment.