Proceedings of the Annual Meeting of the Cognitive Science Society

We investigated the degree to which novel conjunctions of features come to be represented as perceptual wholes. Subjects were trained in a visual search task using novel, conjunctively defined stimuli composed of discrete features. The stimulus sets were designed so that successful search required identification of a conjunction of at least two features. With extended training, the slope of the search functions dropped by large amounts. Various transfer tasks were used to rule out the possibility that the organization of sequential search strategies involving simple features could account for this result. The perceptual discriminability or confusibility of the stimuli exerted an important influence on the rate of unitization. The nature of the perceptual unit appears to depend on the subset of features which are diagnostic for carrying out a particular discrimination task. The results provide important constraints for models of visual perception and recogniHon.