Modality and intermittency effects on time estimation.

The modality of a stimulus and its intermittency affect time estimation. The present experiment explores the effect of a combination of modality and intermittency, and its implications for internal clock explanations. Twenty-four participants were tested on a temporal bisection task with durations of 200-800ms. Durations were signaled by visual steady stimuli, auditory steady stimuli, visual flickering stimuli, and auditory clicks. Psychophysical functions and bisection points indicated that the durations of visual steady stimuli were classified as shorter and more variable than the durations signaled by the auditory stimuli (steady and clicks), and that the durations of the visual flickering stimuli were classified as longer than the durations signaled by the auditory stimuli (steady and clicks). An interpretation of the results is that there are different speeds for the internal clock, which are mediated by the perceptual features of the stimuli timed, such as differences in time of processing.