Are the same attentional mechanisms used to detect visual search targets defined by color, orientation and motion?

Motion information tends to be segregated from color and form information in the visual system, both perceptually and neuroanatomically, and it is therefore possible that different mechanisms of attention are used to select targets defined by these different feature types during visual search. To test this hypothesis, we recorded the N2pc component of the event-related potential waveform during visual search tasks with color, orientation, and motion targets. The N2pc component has previously been shown to reflect a specific attentional mechanism that is present for color and form targets, and we sought to determine whether this component would also be present for motion targets. The N2pc component was indeed observed for motion targets as well as color and orientation targets, consistent with the use of a common attentional mechanism across feature types. In addition, we found that motion singletons (i.e., individual items that moved in the opposite direction from the other items in the array) elicited an N2pc component even when they were task-irrelevant, indicating that motion discontinuities may produce an automatic orienting of attention.