Time perception and the internal clock: Effects of visual flicker on the temporal oscillator

Abstract

Our ability to estimate time intervals has sometimes been attributed to a biological source of temporal information. A model for a temporal oscillator that provides such information has recently been described (Treisman, Faulkner, Naish & Brogan, 1990). This predicts that an imposed stimulus rhythm at certain frequencies may interfere with the temporal oscillator so as to alter its frequency. This interference would cause perturbations in temporal judgements at certain frequencies of the imposed rhythm. The pattern of interference would depend on the frequency at which the temporal oscillator runs, and so would contain information about the oscillator frequency. Evidence for such a pattern was found when auditory clicks at different rates were presented concurrently with time intervals whose durations subjects estimated. The present study examines whether a similar interference pattern can be obtained if visual flicker is substituted for auditory clicks. On each trial, flicker was presented at a rate between 2.5 and 17.5 Hz, concurrently with a time interval to be estimated. A pattern of increased estimates at some rates and decreased estimates at others was obtained. This pattern showed similarities to interference patterns obtained using auditory clicks. This provides evidence that the entrainment of the internal clock predicted by the model can also be produced by visual inputs. Other theoretical implications are discussed.