Search for multiple targets: Remember the targets, forget the search

Models of visual search performance typically assume that search proceeds by sampling without replacement. This requires memory for each deployment of attention. We tested this assumption of memory-driven search using a multiple-target search paradigm. We held total set size constant, varied the number of targets in the display, and asked subjects to report whether or not there were at least n targets present, where n was varied by block. This allowed us to measure the time to find each subsequent target. Memory-driven search predicts that reaction time should be a linear function of n. The alternative memory-free search hypothesis predicts an accelerating function. The data falsify the memory-driven hypothesis. They were consistent with the memory-free search hypothesis but would also be consistent with memory for a small number of previously attended locations.