Set-size effects in visual search: the effect of attention is independent of the stimulus for simple tasks.

In visual search, both attentional and non-attentional sensory processes contribute to set-size effects. Here, non-attentional sensory effects were controlled and the remaining effects matched closely the purely attentional effects measured by a cueing paradigm. Using these controls, set-size effects were measured for five simple and two more complex tasks. The set-size effects were of similar magnitude for all of the simple tasks and larger for the complex tasks. For stimuli in the simple tasks, the results were consistent with the existence of a purely attentional effect on decision processing that is independent of the particular stimulus.