Effects of foveal stimulation on peripheral visual processing and laterality in deaf and hearing subjects

This research examines visual field differences in the detection and identification of a peripheral stimulus for deaf and hearing subjects, as a function of concurrent foveal stimulation. Deaf and hearing subjects were presented with peripheral target stimuli (simple geometric shapes) presented tachistoscopically to the left or right visual fields under four conditions of foveal stimulation: (a) no stimulus; (b) simple geometric shapes; (c) pictorial shapes (outline drawings); and (d) orthographic letters. Dependent measures were detection response latency and peripheral shape recognition (errors). With error data, hearing subjects showed a right field advantage under foveal conditions of no stimulus and simple shape stimulus, but a left field advantage with pictorial and letter foveal stimuli. Deaf subjects showed the opposite effect, with a left field advantage under foveal conditions of no stimulus and simple shape stimulus, but a right field advantage with pictorial and letter foveal stimuli. Latency data revealed the same pattern of results for hearing subjects, but no significant visual field differences for deaf subjects. Results are interpreted in terms of differences in hemispheric visual processing used by deaf and hearing subjects, as affected by varying conditions of foveal load.