Abstract
Aim: Previously we reported a novel uni-directional after-effect termed the regularity after-effect, in which adaptation to a regular pattern caused a slightly less regular pattern to appear even less regular. Here we consider whether the after-effect is mediated by a first- or a second-order process. Method: Stimuli consisted of a 7 by 7 arrangement of elements on a baseline grid windowed through an aperture. The position of each element was randomly jittered from its baseline position by an amount that determined its degree of pattern irregularity. The elements of the pattern consisted of dark Gaussian blobs (GB), difference of Gaussians (DOG) or random binary (RB) patterns. Observers adapted for 60 seconds to a pair of patterns above and below fixation with a different degree of regularity, then adjusted the relative degree of regularity of two subsequently presented test patterns. The size of the after-effect at the PSE was given by the log ratio of the physical element jitter of the two test patterns at the PSE. Results: The after-effect transferred from GB adaptors to both DOG and RB test patterns, and from DOG and RB adaptors to GB patterns. Conclusion: Pattern regularity is an adaptable feature that is encoded by a second-order process. Candidate mechanisms include 1. second-order spatial-frequency channels; 2. the computation of average inter-element distances.
Meeting abstract presented at VSS 2012