Effect of target separation on selective attention.

A visual search task, in which subjects searched circular stimulus displays for two instances of a prespecified target, was used to investigate the effects of target-separation on accuracy. When a comparison was made of the total number of targets correctly located at each separation, no significant differences were found, and this suggested that, within the range of separations (maximum of 2.53 degrees) examined, the selective processing of the relevant items was not influenced by the distance separating them. Also, assuming that the redundancy of target items increased the probability of a target being perceived, the differences between the number of first targets correctly located and the number correct in a single target condition, were in the predicted direction. However, they failed to reach significance.