Central performance drop on perceptual segregation tasks.

The main concern of this study is the range of the central (foveal) performance drop in perceptual segregation tasks reported by Kehrer (Spatial Vision 2, 247-261, 1987). This effect suggests that parafoveal areas of the retina make a significant contribution to the perceptual segregation of textures. Results showed that: (1) the central performance drop was not due to retinal criterion shifts in the sense of signal detection theory; (2) the central performance drop was not restricted to very short presentation times but could also be observed in 80- or 120-ms presentation times; (3) the retinal area in which maximal segmentation performance was found could be shifted by manipulating the spacing between the elements of the stimulus. This finding suggests that each different area of the retina is linked to the processing of a specific, limited area of the spatial frequency band.