Talk of Hao Tam Ho on December 7th at 4pm
Title: Oscillations of perceptual sensitivity and decision bias in audition
In a typical psychophysics experiment, participants are required to detect a specific stimulus or discriminate between two different stimuli presented repeatedly over many trials. Often stimulus properties are kept constant throughout the experiment and nevertheless accuracy fluctuates from trial by trial, such that on some trials target detection or identification is highly accurate, while on others the same stimulus may be missed or misidentified. These fluctuations in performance have been attributed to various factors, primarily attention which can intermittently wane in the course of an experiment. Recent evidence from visual studies suggests that these behavioural fluctuations are far from random or irregular but instead follow a slow regular rhythm of ~4-10 Hz. This observation aligns with electrophysiological findings showing that the periodic decreases and increases in visual performance correlate with the changing amplitude and phase of ongoing brain oscillations at corresponding frequencies. Attempts to reveal similar correlations between behaviour and brain oscillations in audition have been mostly unsuccessful with scalp EEG. Here, we use a purely behavioural sampling technique to show the existence of low-frequency oscillations in auditory performance. Applying Signal Detection Theory, we find that perceptual sensitivity (d-prime) and decision bias (criterion) oscillate at different frequencies, with sensitivity exhibiting a slower rhythm, ~6 Hz, than bias, ~9 Hz. We provide evidence that these oscillations in performance are likely driven by hysteresis.