Collinear facilitation: effects of additive and multiplicative visual noise

Abstract

Purpose 1) To assess whether collinear facilitation is limited to absolute detection threshold, we investigated the influence of additive 2-D visual noise. 2) to assess whether collinear facilitation is limited to 1^st order processing pathways, we assessed whether it occurs for 2^nd order stimuli. Methods. In a standard collinear facilitation paradigm, we used a standard 2 AFC procedure to measure the detectability of Gabor stimuli to which visual noise was either added or multiplied. Results 1) we found that collinear facilitation is limited to at or around absolute threshold, not being present for stimuli with significant amounts of added visual noise, 2) 2^nd order stimuli can show collinear facilitation, but of a reduced magnitude, and 3) we found no crossed facilitation from 1^st to 2^nd order stimuli or visa versa. Conclusion. Collinear facilitation is not ubiquitous throughout the contrast range and does occur for some 2^nd order stimuli. Neither result is consistent with it having a pivotal role in contour integration.