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Similarity between concurrent visual discriminations: Dimensions and objects.
Perception and Psychophysics, 54, 425-430.
Year of publication:
Accuracy is often reduced when two visual discriminations must be made concurrently ("divided attention"). According to a hypothesis proposed originally by Treisman (1969) and Allport (1971), this result should depend on the similarity of required discriminations. When discriminations concern different visual dimensions, they should be made in somewhat separate visual subsystems, reducing interference between them. This prediction is tested in two experiments, involving discriminations of shape, size, orientation and spatial frequency. In different conditions of divided attention, concurrent discriminations concern either the same or different dimensions, and either one or two objects. The results show that performance depends only on the number of relevant objects, not the number or similarity of required discriminations. They suggest that selective attention to an object is a coordinated state in which the outputs of multiple visual subsystems are made concurrently available for control of behaviour.