Perceptual grouping by similarity and proximity: experimental results can be predicted by intensity autocorrelations

A model for perceptual grouping based on measurements of spatial correlations is proposed and tested. Gestalt-like grouping experiments were performed to study and quantify the effect of element similarity (shape, luminance) and proximity. Observers reported the horizontal or vertical organization of stimuli with proximity and similarity providing conflicting grouping cues. Proximity grouping was found to be perceived much faster than similarity grouping. However, with increasing processing time, similarity was found to dominate grouping. The experimental results can be accounted for by assuming a process that compares horizontal and vertical intensity autocorrelations. The model suggests that correlations are measured across a limited spatial range, and that this range increases with processing time.