PSYCHOPHYSICAL END-STOPPING ASSOCIATED WITH LINE TARGETS

Increment threshold for a small (e.g. 1' x 5') line target superimpose d on backgrounds of various shapes and sizes was measured to provide a detailed map of the spatial interactions about line targets. This mod ified ''Westheimer paradigm'' indicated sensitization in the length di rection as well as in the width direction around the line target. The effect of the adaptation field summed over an elongated, end-tapered c entral region, and showed strong end-zone antagonism beyond the ends o f the elongated summation area, as well as flank antagonism to the sid es. Secondary disinhibitory and inhibitory areas outside of the antago nistic surround were also demonstrated. When length of the test line w as varied, the length of the summation region increased concomitantly, while the length of the end-zones remained fixed. End-zone antagonism was slightly weaker at oblique orientations, These results demonstrat e a perceptual analog to neurophysiological end-stopping, and suggest a multilobed gamma-dimension weighting profile appropriate for models of spatial visual abilities. Copyright (C) 1996 Elsevier Science Ltd.