Directional anisotropies in preferred and perceived auditory interpersonal distance of footsteps

Maintaining appropriate interpersonal distance (IPD) is essential for safe and comfortable interactions. While previous research has shown that the preferred IPD exhibits directional anisotropy around the body, inconsistent patterns have been reported due to methodological differences and limitations of visual modality when comparing the front and rear spaces. In two experiments, we examined the extent of the auditory personal space around the body by measuring the preferred IPDs for actual footsteps using an auditory version of the stop-distance task, which exploits the omnidirectional sensitivity of the auditory system. Across two experiments, participants preferred a greater IPD for footsteps approaching from the front compared to the rear and lateral directions, consistent with the vision-based findings. We also measured the perceived IPD of footsteps and found that rear footsteps were perceived as more distant. Experiment 2 found that a faster tempo of footsteps increased the preferred but not perceived IPD, suggesting distinct mechanisms underlying auditory distance estimation and IPD regulation. Moreover, correlation analysis revealed that individuals who perceived footsteps as closer preferred greater IPD, suggesting a proactive spatial buffer against perceived proximity. Finally, when adjusting for the preferred IPD by directional bias in the perceived IPD, the adjusted personal space was greater in the rear direction than in the other directions, suggesting that discomfort with footsteps occurred at a greater perceptual distance behind the body. Altogether, our findings provide evidence of directional anisotropies in personal space and distance perception in the auditory domain, contributing to the understanding of comfortable interpersonal communication in a three-dimensional environment.