Inter-trial priming is not sufficient for feature-based distractor suppression

Previous research has shown that observers can learn to suppress a salient distractor (e.g., a unique red item among green ones) when its salient feature (red) remains constant. Several authors suggested that such suppression builds up through repetition of the distractor's salient feature via intertrial priming. Support for this account primarily comes from the finding that interference from a salient distractor is weaker when this distractor's salient colour repeats on successive trials than when the distractor takes on the previous target's colour. Here, we tested an alternative account, unrelated to distractor suppression, according to which this priming effect reflects increased distraction when the salient distractor shares the previous target's colour rather than a decreased distraction when this distractor's colour repeats. To dissociate the two accounts, we randomly selected the distractor and the other search items' colours from four possible colours. Thus, on successive trials, the distractor and target colours could repeat, be new or swap. We found that relative to the new-colour condition, distractor interference increased when the distractor took on the previous target colour, but was unaffected by whether the distractor's colour repeated. Our findings challenge the claim that intertrial priming accounts for distractor suppression.