Influence of cross-trial distractor volatility on statistical learning of spatial distractor suppression

Learning to suppress location(s) where a distractor frequently occurs can improve search efficiency, known as distractor-location probability-cueing. However, the impact of the volatility of distractor occurrence - how often distractor-present and - absent events switch - remains poorly understood. To investigate this, we contrasted two volatility regimens in an additional-singleton search paradigm: a low-volatility environment in which distractor-present trials tended to occur in streaks, and a high-volatility environment with more frequent alternations. The distractor appeared 13 times more often at a designated frequent location than any rare locations. We replicated the probability-cueing effect, which was consistent across both volatilty conditions. Interestingly, the target-location effect - slower responses to a target at the frequent distractor location - was robust in the high-volatility condition, but non-significant in the low-volatility condition. We propose a suppression-thresholding account: the activation threshold of the saliency-triggered suppression mechanism is dynamically adjusted based on the volatility and local frequency of distractor occurrence.