Inhibition in large set sizes depends on search mode, not salience

Attention can be attracted to salient items in a visual scene. Recent studies have shown that when the feature of an irrelevant salient item is known, it can be suppressed below baseline leading to facilitated search. Wang and Theeuwes (Experimental Psychology: Human Perception and Performance, 46(10), 1051-1057, 2020) criticised previous inhibition studies by claiming that the sparse displays attenuated the salience of the distractors. In their study they increased the number of display items (i.e., set size), and found that an irrelevant salient distractor captured attention. The current paper argues that the displays used by Wang and Theeuwes encouraged participants to use a singleton search mode, in which participants actively look for salient regions to find the target and consequently do not inhibit salient items. Specifically, their displays included multiple repeated non-target shapes, so that the target became a singleton. We used two search displays with ten items, one with repeated non-targets (R-NT displays), allowing a singleton search mode, and one with heterogeneous non-targets, encouraging a feature search mode. In Experiment 1 the singleton distractor was inhibited in the heterogeneous condition, but not in the R-NT condition. Experiment 2 intermixed the two display types in unbalanced blocks. When the majority of trials had heterogeneous non-targets, inhibition was observed for both the heterogeneous displays and the R-NT displays. Conversely, when R-NT displays were the majority, inhibition was attenuated for both display types. These results show that distractor features can be suppressed at large set sizes dependant on the search strategy promoted by the displays.