Visual estimation of the direction of complex moving patterns by domestic chickens (Gallus gallus): A behavioural analytical approach

Abstract

Humans and nonhuman primates are able to combine ambiguous directions of movement in a scene into a global motion percept and are able to solve the problem of estimating motion direction. There is extensive research on motion perception in humans, mammals and some avian species but little is known about the motion perception capabilities of the domestic chicken. We investigated whether domestic chickens are capable of determining global motion direction and developed methods whereby they were able to reliably indicate their direction estimates. A number of preliminary directional learning training conditions were used in order to teach the birds to selectively respond to moving patterns (sine wave gratings) which were moving in one of three directions (45°, 135° or 90°). Once this learning had occurred and was reliable, we presented ‘plaid’ probe trials which were summed gratings moving at 45° and 135°. Humans and nonhuman primates perceive this combined plaid pattern to be moving upwards at 90°. The experiments investigated whether the birds perceived upwards (90°) motion or the two diagonal directions separately when shown the plaid probe stimuli. The data show that the domestic chickens in our study were able to make directional judgements based on motion cues (they could reliably indicate 45° and 135° directions) but did not perceive the combined upward (90°) global motion as humans and nonhuman primates do. This suggests that they process visual motion differently from us.