Individual Alpha Frequency Predicts the Sensitivity of Time Perception
A growing body of research links individual differences in the frequency of alpha-band oscillations to temporal aspects of perception. However, whether the human alpha rhythm is a correlate of time perception itself has remained controversial. This multi-day study combined EEG with multiple duration estimation and discrimination tasks in order 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 1200 to 100ms). In a temporal estimation task, participants (n = 55) 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 dynamic (varying randomly over time). We found that IAF was significantly related to the variance of duration estimates, a measure of precision (or sensitivity), but not average duration estimates, a measure of bias. Further supporting this relationship, psychometric function slopes obtained from independent duration discrimination tasks were correlated with IAF, particularly for the static stimulus conditions. These effects were largely consistent across the range of stimulus durations tested and held when controlling for participant age. Taken together, these results suggest that IAF plays a role in shaping individual differences in the sensitivity of time perception. However, we did not observe effects of spontaneous fluctuations in single-trial alpha frequency, suggesting the effect is primarily observable at the cross-subject level.