Agents' awareness of visuo-motor incongruency determines changes in haptic sensitivity.

When body movements are transformed into somewhat discrepant effects in the environment, agents are surprisingly unaware of what their body is doing exactly (e.g., Knoblich and Kircher 2004; Fourneret and Jeannerod 1998; Sutter et al. 2008). Presumably, that is because agents control such movements primarily via their transformed visual effects while downregulating the processing of haptic movement effects (for a review, see Sutter et al. 2013). In two experiments, we measured tactile sensitivity on the moving effector as a proxy for the up- or downregulation of processing haptic effects during continuous visuo-motor congruent or incongruent tool transformations. As expected, tactile sensitivity was modulated by incongruency, but only when individuals became aware of it. Awareness came with an increase in tactile sensitivity, suggesting that haptic processing is upregulated once agents notice that their movements are not congruent with intended visual effects. These findings challenge the presumed dominance of environment-related action consequences in movement control, demonstrating the breakthrough of tactile perception in case of visuo-haptic incongruency.