A Correlate to Mach Bands in Perception of Extent

Abstract

It is demonstrated that contours which vary in extent across space according to the Mach pattern include an increment in apparent extent and a decrement in apparent extent at a position corresponding to the position of Mach bands, i.e., at the inflection points of the pattern. It is also shown that increasing the slope of the gradient of the Mach pattern has an effect upon extent comparable to the effect upon Mach bands. These data are interpreted as supporting the position that lateral inhibitory interaction is involved in the perception of extent. A modification of the Hartline and Ratliff (1956) model for lateral inhibitory interaction is applied, and discrepancies between predictions generated from the model and obtained data provide the basis for recommended changes in the model.