LOCALIZATION OF A PERIPHERAL PATCH - THE ROLE OF BLUR AND SPATIAL-FREQUENCY

Peripheral vision serves to direct our attention and fixation to objec ts of interest, This requires that the visual system be capable of acc urately localizing peripherally presented targets having different spa tial structures, The question we address is ''to what extent does stim ulus spatial structure influeuce the precision of peripheral localizat ion?'' To address this issue, we measured the precision of spatial loc alization (with reference to a foveal target) for a single Gaussian or Gabor patch briefly presented in the periphery, For both stimuli, we find that when the standard deviation of the stimulus envelope (SD) is less than 1/5 the stimulus eccentricity, localization thresholds are independent of SD and are approximately 1/50 of eccentricity. For larg er values of SD, localization thresholds increase linearly with increa sing SD, and are approximately 1/5 of SD, The results hold over a rang e of eccentricities (from 2.5 to 10 deg) and stimulus contrasts (from near detection threshold to 80%), In addition, for Gabor patches, the results are independent of frequency, phase and orientation of the car rier. Copyright (C) 1996 Elsevier Science Ltd.