The effect of adapting luminance on the latency of visual search

Computational models of attentional processing typically view the "attentional spotlight" as a winner-take-all network whose focus can be shifted serially about a display if required. As a result, lateral inhibition is assumed in these models to be an important mechanism involved in visual search. On the basis of this assumption, we predicted that changes in adapting luminance would produce specific changes in search latency functions in virtue of affecting visual inhibition. The results of our first two experiments confirmed these predictions: when search was difficult, and produced reaction time results characteristic of serial processing, there was a main effect of adapting luminance and a significant interaction between adapting luminance and the number of display elements. These effects were both reflected in increases in the slopes and the intercepts of average search latency functions when adapting luminance was decreased. When search was easy, and produced pop out effects characteristic of parallel processing, there were no significant effects of adapting luminance on search latency. The third experiment used adapting luminance to further explore the possibility that arrow junctions are detected preattentively. The results suggested that a visual search for such elements involves a substantial serial component, which weighs against the claim that they are detected by low-level vision.