Visual perception and stimulus orientation in cattle

The pupil in the eye of adult cattle is oval under contraction with the lon g axis nearly horizontal. Based on simple optophysical facts it is hypothes ised that visual perception in such eyes is different for stimuli with vert ically separated details rather than stimuli with horizontally-separated de tails. This hypothesis was tested with three adult dairy bulls using an ope rant conditioning technique. The bulls had to discriminate a solid white li ne from broken white lines with decreasing interspaces. They solved this ta sk better when the stimuli were presented vertically rather than horizontal ly. This result is discussed in terms of visual acuity and related to the t opographical anatomy of the eye, particularly the pupil. (C) 2000 Elsevier Science Ltd. All rights reserved.