Higher set sizes in pop-out search displays do not eliminate priming or enhance target selection

Previous research shows that salient stimuli do not pop out solely in virtue of their feature contrast. Rather, visual selection of a pop-out target is strongly modulated by feature priming: Repeating the target feature (e.g., red) across trials primes attention shifts to the target but delays target selection when the target feature changes (e.g., from red to green). However, it has been argued that priming modulated target selection only because the stimuli were too sparsely packed, suggesting that pop-out is still mostly determined by the target's saliency (i.e., local feature contrast). Here, we tested these different views by measuring the observer's eye movements in search for a colour target (Exp. 1) or size target (Exp. 2), when the target was similar versus dissimilar to the target, and when the displays contained 6 or 12 search items. The results showed that making the target less similar to the nontargets indeed eliminated priming effects in search for colour, but not in search for size. Moreover, increasing the set size neither increased search efficiency nor eliminated feature priming effects. Taken together, the results indicated that priming can still modulate target selection even in search for salient targets.