Akira Sarodo¹ (), Katsumi Watanabe¹, Shao-Min (Sean) Hung^1,2; ¹Faculty of Science and Engineering, Waseda University, ²Waseda Institute for Advanced Study, Waseda University

Numerous evidence suggests that the human visual system both implicitly and explicitly extracts statistical regularity. However, the interaction between the implicit extraction and explicit knowledge of the statistical regularity remains unclear. In the present study, we adopted an exogenous cueing paradigm and manipulated cue-target congruency across the blocks (50%, 60%, 70%, 80%, 90%, 100%) to examine whether the explicit knowledge regarding the cue-target congruency affects the implicit cueing effect. Participants were asked to perform an orientation discrimination task on target. In Experiment 1, we increased the cue-target congruency from 50% to 100% and found that reaction time to the invalid cued target increased as the cue-target congruency increased, whereas the congruency had no impact on the reaction time to the valid cued targets, showing an incongruency penalty. This incongruency effect was observed even when the congruency was at chance (50%) and regardless of the explicit awareness of the cue-target congruency. Experiment 2 replicated this incongruency effect with decreasing cue-target congruency from 100% to 50% across the blocks. Two follow-up experiments with a fixed congruency (70%) demonstrated that explicit knowledge regarding the cue-target congruency from either an explicit prime or self-estimation did not alter the size of the penalty effect. That is, the penalty effect tracked the actual congruency rather than the perceived contingency. These results further showed that the explicit knowledge played only a trivial role in the incongruency penalty effect. This series of psychophysical experiments implies that the human visual system tracks the statistical regularity to optimise behaviour even without explicit awareness of the regularity.