Pigeons' Near-Field Visual Acuity for Hi-Vision Video Monitor

Abstract

The near-field visual acuity in three pigeons was measured in apparatus that employed a Hi-Vision Video monitor (HDTV) as a stimulus-display device. The pigeons' visual acuity for the standard NTSC video display has not been examined because of its low picture resolution. The spatial resolution of Hi-Vision video system (1125 lines/display) was higher than that of NTSC system (525 lines/display). Pigeons were trained to discriminate a grating stimulus from a blank stimulus of equivalent luminance. The stimuli were presented on the Hi-Vision display behind the transparent keys. A peck on the grating key was reinforced. The distance from the stimulus to the eye was determined by a method of behavioral fixation. The spatial frequency of grating stimuli was varied in each session according to the performance of discrimination. Thresholds ranged from 3.9 min to 11.7 min. These psychophysical data were approximate to the acuity measured with the photographic projection systems. These results suggest that Hi-Vision video display permits sufficient spatial resolution for measuring the pigeons' near-field visual acuity.