Interpersonal Distance Task - Looming Footsteps Sound Effect

Participants are asked to listen to six audio clips consisting of the sound of footsteps approaching them from the front. In half of the trials, participants are asked to indicate “Stop” when the person heard approaching made them feel uncomfortable with the interpersonal distance. In the other half of the trials, participants were asked to indicate “Stop” when they felt like they could touch the person they heard coming towards them. The order of these two tasks is counterbalanced across participants. In each case, the response times (RT) in milliseconds, i.e. the time taken to indicate “Stop”, is measured, with a longer RT indicating smaller boundaries of space. The task distinguishes between types of peripersonal representations: the former representation being involved in protecting the body, and the latter in goal-directed action. As such, we dissociate between interpersonal and reaching distances. Here we adapted the auditory task by Vagnoni and colleagues (2018) to capture RD to compare with IPD. The walking sound effects were generated and recorded using Unity 3D (Unity Technologies, 2020). Free footstep sounds were downloaded from https://freesound.org/ and were split into single files, one file per footstep. A unity script loaded the footstep audio files when a walking animation was executed and synchronised each sound with the animation. A unity scene with an audio reverb zone was created with a maximum distance of 36 metres. An audio listener was located inside the reverb zone which allowed one to gradually change the footstep sound effect as the animation slowly moved closer to the target. The output was generated using the Unity Recorder tool.