Learned suppression is based on a proactive mechanism

In learned suppression, repeated exposure to a specific salient singleton distractor color during visual search leads to a learned ignoring of the otherwise strong bottom-up signal from the distractor. One remaining question is whether this ignoring is based on a pre-search preparatory suppression of the learned color, or a reactive mechanism after attention is captured by the salient distractor during visual search. Previous research has focused on responses to the distractor during search, making it impossible to know if the effects are based on a preparatory suppression. Here, we use SSVEP to measure the pre-search response to the learned distractor color compared to other colors. The neural response to the learned distractor color was suppressed compared to the other colors, providing the first evidence that the mechanism of learned distractor suppression is present in the pre-search period. This result is in line with the predictions of a proactive color-specific suppression in learned suppression.