Force feedback facilitates multisensory integration during robotic tool use.

The present study investigated the effects of force feedback in relation to tool use on the multisensory integration of visuo-tactile information. Participants learned to control a robotic tool through a surgical robotic interface. Following tool-use training, participants performed a crossmodal congruency task, by responding to tactile vibrations applied to their hands, while ignoring visual distractors superimposed on the robotic tools. In the first experiment it was found that tool-use training with force feedback facilitates multisensory integration of signals from the tool, as reflected in a stronger crossmodal congruency effect with the force feedback training compared to training without force feedback and to no training. The second experiment extends these findings by showing that training with realistic online force feedback resulted in a stronger crossmodal congruency effect compared to training in which force feedback was delayed. The present study highlights the importance of haptic information for multisensory integration and extends findings from classical tool-use studies to the domain of robotic tools. We argue that such crossmodal congruency effects are an objective measure of robotic tool integration and propose some potential applications in surgical robotics, robotic tools, and human-tool interaction.