Size constancy induced by context elements/Größenkonstanz im Kontext

Abstract

An illusion concerning the apparent length of a horizontal line was induced by superposition of geometric elements, ie five vertical stripes or a circular line, respectively. These contextual elements were varied in size which is equivalent to a variation of their information density. In several experiments, the perceived length of the line has been found to increase as a function of the information density of the pattern. This is interpreted as due to a size constancy effect, ie the conspicuity range is reduced, to achieve better resolution of closely spaced stripes or a small circular line. This affects the perceived length of the target line, too. From this conceptual model the mathematical functions y(x)=A·x ^- ^n, y(x)=A·x ^n, and y(x)=A·x ^n^·^exp^(-B·x) are derived and fitted to the results of the experiments, with n being the size constancy parameter. Depending on the experimental conditions, values of n= 0.0756(77), n=0.058(12), n=0.0366(94), and n=0.0503(57) are obtained.