Tutku Öztel¹ (), Martin Wiener¹; ¹George Mason University

Human time perception is subjective. This subjectivity renders timed intervals prone to illusory percepts induced by stimulus psychophysical properties. One robust example for stimulus-induced temporal illusions is the leftward shift in psychometric functions associated with p(long) responses for timed durations as a function of stimulus velocity (Karsilar, Kisa & Balci, 2019). Recently, we have shown that subjects are unaware when illusory distortions in time occur, as shown by a lack of metacognitive insight (Öztel & Balci, 2020). What we still do not know about this metacognitive inability is how (1) stimulus-induced temporal illusions are represented and (2) if at all, metacognitive processes associated with these illusions are encoded at neural level. To address these questions, we recorded 64-channel electroencephalogram (EEG) activity in human adults (n = 26) in a temporal bisection task where participants classified the duration (1-3.5s) of an animated walking stickman figure with different velocity (i.e., 25, 50, 100 fps*) as being short or long and reported their confidence. Behaviorally we replicated our previous findings wherein faster velocities led to longer reported intervals, as well as lower precision yet faster reaction time; in contrast, confidence judgments did not vary with psychophysical shifts, only tracking reaction time. To our surprise, common EEG signatures of time perception, such as the frontocentral contingent negative variation (CNV) or late positive component of timing (LPCt) (Wiener & Thomspon, 2015; Ofir & Landau, 2022) 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. We further observed that these effects were driven by entrainment to walking speed. Altogether, our findings suggest that temporal illusions are engaged by bottom-up sensory processes, but fail to reach the metacognitive level; in contrast, metacognitive insight for time appears largely related to top-down sampling of motor output.