On the functional differences between frontal and lateral visual fields of the pigeon.

Abstract Many studies of the pigeons' visual discrimination, determined by operant conditioning techniques, have suggested that the pigeon eye has a tendency to be myopic in the anterior visual field and hyperopic in the lateral field. The results of four experiments are reported in which pigeons were required to discriminate image structure, motion, color and luminance. All of these experiments showed that pigeons perform poorly if the stimuli are located in the lateral visual fields, and evidence from two experiments suggests that the failure to respond is not due to an inability to focus accurately. Moreover, ray diagrams calculated and traced by a computer, from data obtained from frozen sections through the pigeon eye, indicate that the eye may be capable of accommodating objects in the lateral field lying at a distance of only a few centimeters. It is hypothesized that the reason for the pigeon's apparently poor discriminative performance in the lateral direction is due not to an inability to accommodate but to the fact that, by virtue of its evolutionary inheritance, the pigeon is not “prepared” (i.e. does not possess the neural capacity) to develop a direct associative pecking response to a laterally located stimulus.