Spatial attention: effect of position uncertainty and number of distractor patterns on the threshold-versus-contrast function for contrast discrimination

Our goal is to integrate knowledge about contrast discrimination with knowledge about spatial attention effects, rin experiment is described that measures the effects of position uncertainty, number of distractors, and contrast on the contrast discrimination threshold in a fully crossed factorial design. The threshold-versus-contrast function is nonmonotonic in all conditions, decreasing and then increasing as contrast increases, increasing uncertainty and/or the number of distracters increases thresholds, and there are interactions among the three variables indicating that uncertainty and distracter number have different effects on detection as distracter contrast varies. The results are well accounted for by a model that combines a nonlinear excitation/divisive inhibition model of pattern mechanisms with a noise-limited model of the decision process. (C) 1998 Optical Society of America.