RELATIVE ROLES OF RESOLUTION AND SPATIAL INTERFERENCE IN FOVEAL AND PERIPHERAL-VISION

The rate of change of visual performance with increasing eccentricity of fixation is known to be task dependent. In order to examine eccentr icity-related changes in visual performance when a combination of two different factors influence thresholds, visual acuity in the presence of flanking elements was investigated across the visual field, interfe rence zones increased in extent with eccentricity at a much faster rat e than did resolution thresholds. E(2) values, quantifying the eccentr icity-related magnification required, were 1-2 degrees for resolution and 0.1-0.2 degrees for spatial interference. E(2) values for resoluti on in the presence of flanks depended on the proximity of the flanks a nd their 'weighting' in the task. From the results, the magnitude and extent of spatial interference across the visual field can be describe d quantitatively. Further, the results serve as an example of how obse rved variations in peripheral threshold gradients might be achieved as a combination of underlying factors with different E(2) values.