The spatial extent of lateral interaction was determined for nonoverlapping equal-energy stimuli in a metacontrast design with targets and masks of constant separation but varying width. The weighting functions derived from these data are wholly negative. Unlike previous estimates of spatial extent in metacontrast, based on experiments in which the separation between target and mask was varied, our weighting functions subtend only about 10′ of visual angle, for both monoptic and dichoptic observations. However, the weighting functions resemble those derived from a wide variety of other psychophysical procedures such as sensitization. The differences of estimates of weighting functions are interpreted in terms of two spatial-lateral-interaction systems. One of these systems may depend critically on the proximity of stimuli; the independence of the spatial extent of the system from target size suggests the involvement of an edge mechanism.
RONALD GROWNEY and NAOMI WEISSTEIN, "Spatial Characteristics of Metacontrast," J. Opt. Soc. Am. 62, 690-696 (1972)