1. Department of Psychology, University of Iowa, Iowa City, Iowa 52242-1407, USA

Correspondence to: Steven J. Luck¹ Correspondence and requests for materials should be addressed to S.J.L. (e-mail: Email: steven-luck@uiowa.edu).

Abstract

The perception of natural visual scenes that contain many objects poses computational problems that are absent when objects are perceived in isolation¹. Vision researchers have captured this attribute of real-world perception in the laboratory by using visual search tasks, in which subjects search for a target object in arrays containing varying numbers of non-target distractor objects. Under many conditions, the amount of time required to detect a visual search target increases as the number of objects in the stimulus array increases, and some investigators have proposed that this reflects the serial application of attention to the individual objects in the array²,³. However, other investigators have argued that this pattern of results may instead be due to limitations in the processing capacity of a parallel processing system that identifies multiple objects concurrently⁴,⁵. Here we attempt to address this longstanding controversy by using an electrophysiological marker of the moment-by-moment direction of attention — the N2pc component of the event-related potential waveform — to show that attention shifts rapidly among objects during visual search.

1. Department of Psychology, University of Iowa, Iowa City, Iowa 52242-1407, USA

Correspondence to: Steven J. Luck¹ Correspondence and requests for materials should be addressed to S.J.L. (e-mail: Email: steven-luck@uiowa.edu).