Non-Spatial VR training
Participants were instructed to identify the amplitude modulation in the target sound, and indicate their discrimination through a reaching movement using VR controller. For fast amplitude-modulated sounds, participants reached in front of them, aiming to touch the invisible virtual button placed above the central speaker. For slow amplitude-modulated sounds, participants reached instead the invisible virtual button placed below the same central speaker. As in the Spatial Training feedback procedure, the sound stopped only when a correct response was provided. If they reached the wrong button, a visual feedback was displayed and the sound continued until the correct button was finally touched. In both trainings, the feeling of touch was induced by making the controller vibrate as soon as it collided with objects (speakers or invisible buttons).