On preventing attention capture: Is singleton suppression actually singleton suppression?

It is commonly assumed that salient singletons generate an “attend-to-me signal” which causes suppression to develop over time, eventually preventing capture. Despite this assumption and the name “singleton suppression,” a causal link between salience and suppression has not yet been clearly established. We point out the plausibility of a simple alternative mechanism: distractors might be suppressed because they are distractors rather than targets, even when non-salient. To look for evidence of salience-based suppression, we had participants search for a target shape among distractors, which sometimes included irrelevant-colored distractors. The critical manipulation was whether the irrelevant-colored distractor was salient (a color singleton) or non-salient (three non-target colored shapes; a triplet). On 30% of trials, probe letters were presented briefly inside each shape and participants were to report those letters. Probe recall below baseline indicates suppression. Experiment 1 showed that suppression was not triggered any more strongly by salient distractors (singletons) than by non-salient distractors (triplets). Experiment 2 showed that strong suppression effects developed rapidly even in the absence of salient singletons. These findings raise the thus far neglected question of whether salience plays any role in suppression.