The influence of salience and similarity on selective attention

A previously reported effect of similarity on reaction times in a categorization task (Hahn et al., 2010) is tested and extended by using eye trackers as a measure of visual attention. The original effect was not found using a new stimulus set, suggesting that delayed reaction times are not a result of dissimilarity but are due, in part, to the properties of the stimuli. The elements of the stimulus reflecting similarity to the training set, but irrelevant to categorization, are made salient to test this idea. The reaction time effect is not replicated, but a surprising result is found in the eye tracking data: attention to irrelevant information is less likely when the irrelevant information is salient. This finding cannot be explained completely by existing models, so a new way of thinking about visual attention is provided in a proposed model of integrated bottom-up and top-down visual attention processes.