Fig. 1
Experiment description. (a) Apparatus. Participants wore a head-mounted device (HMD) that presented the visual stimuli. In addition, a stereo camera was placed 1 m behind the participant, which captured images behind their back. A program, created in Unity, was executed to present the left and right camera images captured by the stereo camera to the HMD’s left and right eye, respectively. The projected image is presented. (b) Experimental task. The experimenter moved a non-sounding bell in front of the camera at 1 Hz. This movement was also reflected in the image projected on the HMD. The participant saw the bell move as a visual stimulus. Synchronized with this movement, a sounding bell was moved in front of the participant as an audio stimulus. This made it seem as if the sound of the bell could be heard from that position by the movement of the bell in the video. (c) Experimental protocol. In each condition, task and threat to the camera for Questionnaires 2 and 1 were administered. Questionnaire 2 was administered after all the conditions. (d) Overall experiment. (Written informed consent was obtained from the participants in the figures for the publication of identifying information/images in an online open-access publication.).
