The effect of target specification on objects fixated during visual search

When a person searches for a target in a cluttered visual field his eye fixations typically fall on objects. The effect of target specification on the probability of fixating different classes of objects was studied. For fields containing objects differing widely in size, color, and shape: a high proportion of searchers’ fixations were on objects of a specified color, a moderate proportion of their fixations were on objects of a specified size, and a s light proportion of their fixations were on objects of a specified shape. When two or more target characteristics were specified, fixations were generally based on a single characteristic. It is proposed that the specification of a target creates a perceptual structure which the searcher explores. The study of visual fixations, in effect, is the study of the perceptual structure.