The Vestibular System Influences the Perceived Duration of Lights But Not of Sounds or Touches.

Accurately perceiving the duration of stimuli is important for many human behaviours, especially those involving movement such as when catching a ball. However, perceived duration is reportedly different depending on which sense is being monitored, with auditory stimuli often judged as longer than a matched visual stimulus. Recent experiments have implicated gravity in duration perception, but rigorous psychophysical methods have been lacking. Here, we developed a novel psychometric method for measuring perceived duration and manipulated the reliability of gravity by altering posture and by disruptive galvanic vestibular stimulation (dGVS). We assessed people's judgements of 1 s using visual (an LED), auditory (200 Hz at 56 dB played through headphones) or tactile (200 Hz played through tactors mounted on the backs of the hands) stimuli. Participants judged whether each stimulus, the duration of which was controlled by a QUick Estimation by Sequential Testing (QUEST) staircase, was longer or shorter than their internal estimate of 1 s in two postures: supine and standing. We also compared visual duration judgements in the presence of dGVS with those collected during sham stimulation to the neck. The perceived durations of auditory and tactile events were not affected by changing posture, but the perceived duration of a visual second was significantly longer when supine compared to when upright (by 45 ms) or during dGVS compared to during sham stimulation (by 66 ms). The duration of a light or tactile stimulus perceived as having a duration of 1 s was longer than the time needed for an auditory event to be perceived as being on for 1 s. We conclude that disrupting the vestibular system by lying supine or by electrical stimulation influences visual duration perception, but the perceived duration of auditory and tactile stimuli remains unaffected.