Families of models for gabor paths demonstrate the importance of spatial adjacency

This paper reports psychophysical and modelling results concerning the contour-detection paradigm of D. J. Field, A. Hayes, and R. F. Hess (1993). We measured psychophysically the maximum tolerable contour curvature (path angle) as a function of contour length. We compared these data to the predictions of an association field (D. J. Field et al., 1993) model based on the relative positions and mutual orientations of nearby elements and to models that explicitly link adjacent elements into chains and characterize each chain by its sequence of contour bends. For every stimulus, a large set of chains is produced and the target identified as the chain with the lowest maximum bend. We tested two different types of linking process: isotropic (linking one element to any other nearby) and anisotropic (linking one element to any others nearby along the orientation of its axis). All of these models can account for our data. Moreover, we show that the pattern of results due to path angle is principally a product of the distribution of spurious contours in the randomly oriented background. Given that some of the models do not embody constraints of orientation relationships between linked elements, this finding shows the importance for early vision in deciding which local elements are to be associated.