Serial processing and the parallel-lines illusion: length contrast through relative spatial separation of contours.

Abstract

The distortion of perceived line length produced by the parallel-lines configuration reversed fromassimilation to contrast with large suprafoveal spatial separation of the contextual and test lines (Experiment 1). This new contrast effect was predicted by a pool-and-store model of size distortion (Girgus & Coren, 1982). However, contrary to the predictions of the model, the amount of spatial separation needed to produce the reversal did not depend on an absolute visual-angle (foveal) measure of separation. Rather, the reversal was determined by the relative spatial separation of contextual and test lines (Experiment 2); that is, small test lines required a smaller spatial separation from a contextual line to produce contrast than did larger test lines. On the basis of these findings, a revised pool-and-store model of length distortion is proposed.