Blinded by motion: Electrophysiological decoupling of time dilation and confidence

Abstract

The duration of visual stimuli can be altered by stimulus features, such as size, brightness, and motion. Recently, we observed that motion-induced changes in perceived duration also shift confidence judgments, but do not track awareness of the illusion. How these two effects differ and are instantiated neurally are unknown. We investigated this question by replicating our previous finding, in which human subjects (n=27) performed a temporal bisection task where they were asked to classify the duration (1-3.5s) of a walking stickman figure with different velocities and provide confidence judgments while 64-channel electroencephalogram (EEG) activity was recorded. Behavioral findings replicated the previous time dilation effect where progressively faster walking speeds led to longer perceived durations. A similar shift was observed for confidence ratings, yet with lowest confidence for the medium walking speed, indicating a metacognitive inability to monitor dilation. Furthermore, common EEG signatures of time perception, such as the late positive component of timing (LPCt) and contingent negative variation (CNV) did not vary with walking speed. Instead, onset-locked responses over occipital electrodes covaried with walking speed and correlated with subject-level shifts in psychometric functions, but not with confidence; conversely, frontocentral responses covaried with confidence judgments, but not walking speed. These findings suggest that temporal illusions are engaged by sensory processes that fail to reach the metacognitive level and that confidence judgments, in turn, are driven by motor estimates read out from frontocentral regions