A method for simulating signal evolution using real animals

We studied response biases to visual stimulation using a new experimental t echnique. The subjects (hens, Gallus gallus domesticus) were confronted wit h several rewarding and non-rewarding patterns on a computer screen. In con trast with standard discrimination tasks the rewarding patterns were not id entical and varied in a dimension differentiating them from the non-rewardi ng patterns. The rewarding patterns changed in response to hens' biases in selection of patterns. The aim of the study was to examine the possibility of receivers being a driving farce in signal evolution. In one of the exper iments a clear-cut result was obtained. During the course of the experiment the rewarding patterns became gradually more different from the non-reward ing one, a result expected from theoretical studies of the effect of respon se bias in signal evolution. A second similar experiment was less conclusiv e, with ceiling and floor effects influencing the results.