Perception of simultaneity and temporal order of active and passive head movements paired with visual, auditory and tactile stimuli

Different senses have different processing times. The consequences of this have been explored in the perceived timing of visual, auditory and tactile stimuli. However the perceived timing of vestibular stimulation, one of the fastest senses to be transduced, has not been systematically investigated. We measured the perceived timing of vestibular stimulation induced passively (head rotated by experimenter in response to ‘go’ stimulus) or under active control (head moved by participant in response to go stimulus). Visual, auditory and tactile stimuli were delivered at various delays from the go stimulus. Participants judged, in separate runs, whether the onset of head movement was simultaneous with the other stimulus (synchronicity judgements) or which stimulus came first (temporal order judgements). Most comparisons required head movements to occur first by between 50-90ms to be perceived as simultaneous, implying that head movements, both passive and active, were perceived after a longer latency than visual, auditory or tactile stimuli. Active movements generally needed a longer lead than passive, suggesting that they had the longest latency, which is consistent with vestibular sensitivity being reduced during active movement. These results will be discussed in terms of the perceived timing of active and passive head movement