Perception of audio-visual synchrony is modulated by walking speed and step-cycle phase.

Investigating sensory processes in active human observers is critical for a holistic understanding of perception. Recent research shows that locomotion can rhythmically alter visual detection performance, illustrating how natural behaviours influence sensory processing. Here, we tested whether the speed and phase of locomotion also modulate temporal perception, focusing on the perceived synchrony of supra-threshold audio-visual stimuli. Participants made synchrony judgements over a range of stimulus onset asynchronies (SOAs) while walking at either slow or natural walking speeds. Slow walking decreased temporal sensitivity and increased reaction times compared to when walking at a natural pace. Further analysis of the shortest SOAs revealed that perceived synchrony was also biased by the relative phase of the step-cycle: with an increased bias to perceive synchrony during the swing phase, and decreased bias at the start and end of each step. Together, these results extend recent evidence that walking dynamically modulates near-threshold visual detection to include the modulation of supra-threshold audio-visual timing judgements.