Diagnostics of parallel and serial processing in a visual search task

We investigated the effect of noise density display organization and the number of stimuli in a visual search task. The results show that when the stimuli were randomly distributed in the visual field, the target was detected in parallel in intact displays and was serially searched in noisy displays; in this case search difficulty increases with noise density. When the display was organized, the search was always parallel. These results suggest that noise and display organization act on early visual processes which affect the size of attentional focus.