Independent and additive effects of repetition of target and distractor sets in active visual search

Priming of pop-out is a well known phenomenon in the literature on visual attention, where the repetition of features from a previous trial facilitates a response to the same feature on the next trial. While such effects have mostly been studied by measuring key-press responses, priming from target repetition has also been found to facilitate saccadic eye movements to targets containing repeated features. Much less studied is priming from repeated context, or distractor-sets. Priming of context is presumably driven by inhibition mechanisms speeding rejection of non-targets. In order to investigate any facilitatory effects of target and context repetition upon latencies of saccadic eye movements, and any interactions between the two, we measured saccades in a color-singleton task where the target color and the color of the distractors varied independently of one another. The task was an “active” visual search where observers had to make a speeded saccade to the center of the singleton target. Repetition of target color and distractor-set color both resulted in decreased saccadic latencies, but the effect was larger for repetition of context than target. In contrast, target repetition had a larger effect upon search accuracy. Because of these discrepancies we calculated inverse efficiency (saccadic latency/percentage correct) to control for possible trade-offs between latency and accuracy. The inverse efficiency analyses showed highly significant effects of repetition of both target and context, with no hint of an interaction between the two. The tight link between attention shifts and eye movement preparation is well documented, and our analyses of priming show that the repetition of both target and distractor-sets has a strong influence upon attention shifts and eye movements and that these effects are independent of one another.