Individual Alpha Frequency Predicts the Sensitivity of Time Perception.

A growing body of research links individual differences in the alpha-band frequency to temporal aspects of perception. However, whether the human alpha rhythm is a correlate of time perception itself has remained controversial. This study combined EEG with multiple duration perception tasks to evaluate whether individual alpha frequency (IAF) is associated with sensitivity or bias in judging visual durations across a range of peri-second durations (spanning 100-1200ms). In a temporal estimation task, participants (n = 55; 38 female, 13 male, 4 non-binary) reported the duration of a single stimulus between 300-1200ms. In a temporal discrimination task, participants reported which of two stimuli was longer: a standard (100, 600, or 1200ms) or comparison (50-150% of the standard). Stimuli also varied in whether their luminance was static or dynamically varying over time. We found that IAF was significantly related to the variance of duration estimates, a precision measure, but not average duration estimates, a bias measure. Further supporting this relationship, psychometric function slopes obtained from the independent duration discrimination tasks were positively correlated with IAF, particularly for the static stimulus conditions. These individual differences effects held when controlling for participant age. We also explored trial-level variability in alpha frequency and found it was predictive of shifts in the point of subjective equality (PSE) during discrimination of very short (100ms). Taken together, these results suggest that IAF plays a role in shaping individual differences in the sensitivity of time perception and that spontaneous variations around one's IAF can lead to a bias in temporal representations.