Practice-dependent changes in body representation but not in reaching distance following virtual tool-use

Prior research has shown that humans tend to integrate virtual tools into their body representation and that this integration is linked to motor performance in tool-use tasks. In the present study, we tested whether, and to what extent, tool-use training influences sensorimotor and spatial representations. To assess these representations, participants completed a tactile distance judgment task and a reaching distance estimation task before and after virtual tool-use training. Training led to a practice-dependent recalibration of tactile distance perception. Even brief exposure (30 trials) produced a measurable reduction in the overestimation of forearm length. However, the strongest recalibration occurred after 120 trials, suggesting that extended practice is necessary for stable adjustments in perceived forearm length. In contrast, reaching distance estimation changed only modestly from pre- to post-test, regardless of training duration, suggesting that perceived reach adjusts rapidly and independently of the amount of training. Arm length was a strong predictor of reaching distance estimation error, with longer-armed participants showing more negative error values, highlighting how stable anatomical properties shape reachability judgments and constrain perceived action space. These findings reveal a possible mechanistic dissociation between tactile body metrics and perceived reachable space. While action boundaries expand rapidly and independently of practice, the perceived metric of the limb itself appears to require cumulative sensorimotor evidence to overcome stable biological priors.Keywords: Tool-use, visual feedback, body representation, peripersonal space, distance estimation