ABSTRACT
The process by which we locate a target in a cluttered visual scene has been the topic of fierce debate for the past several decades. While the obvious reason for this debate is that many competing models do an excellent job of describing the basic search phenomenon (an increase in manual reaction time [RT] with the number of objects in the display), a more distal cause may be linked to a limitation of the dependent measures commonly used to study search. For example, one popular class of models liken search behavior to the movements of a fixed-diameter beam or spotlight (Treis-man et al, 1980, Treisman, 1988). The more items in a display, the more times this spotlight must move, resulting in longer search times. Note however that this very specific theory about the spatial evolution of search over time is being inferred from a RT result without any direct measure of this spotlight or its movements. This failure to directly measure the theoretical construct in question opens the door for other models of search to offer their own explanations for why RTs increase with set size. In this sense a RT measure simply lacks the resolution needed to unambiguously describe the spatiotemporal changes occurring during search.
