Andrew Rodriguez¹ (), Morgan R. Dodd¹, Mark W. Becker¹; ¹Michigan State University

In visual search literature, evidence for feature-based suppression (FBS) has been controversial and mixed. Much of the mixed findings are due to differences between implicit FBS, the unconscious ignoring of a feature that appears as a distractor with high regularity, and explicit FBS, the active biasing of attention away from a feature. Given this discrepancy, we examined the benefits of implicit and explicit FBS in a Landolt C search task. Across four experiments, we had participants search for a C with a horizontal gap among several distractor Cs with vertical gaps. This search task had two phases. The first phase had one color (ignored color) that appeared on a higher percentage of trials (80%) and always appear as a distractor. The second phase removed the contingency - the previously ignored color now could appear as the target. For the experiments that measured the implicit suppression effect, participants were not made aware of the ignored color. For the experiment that measured the explicit suppression effect, participants were cued that the target would not appear in the ignored color. Our results showed a robust implicit suppression effect, with faster RTs when the ignored color was present as a distractor than when ignored color was absent. Furthermore, the implicit suppression benefit required minimal training of the to-be-ignored feature and persisted even when participants were given positive cues about the target’s color. However, we found a weak effect of explicit suppression that required extensive training before it became beneficial. Our findings suggest that implicit FBS can effectively guide attention while explicit FBS is ineffective unless there is ample training of the to-be-ignored feature, limiting its utility as a real-world mechanism for allocating attention.