Haptic Human-Human Interaction Through a Compliant Connection Does Not Improve Motor Learning in a Force Field

Abstract

Humans have a natural ability to haptically interact with other humans, for instance during physically assisting a child to learn how to ride a bicycle. A recent study has shown that haptic humanhuman interaction can improve individual motor performance and motor learning rate while learning to track a continuously moving target with a visuomotor rotation. In this work we investigated whether these benefits of haptic interaction on motor learning generalize to a task in which the interacting partners track a target while they learn novel dynamics, represented by a force field. Pairs performed the tracking task and were intermittently connected to each other through a virtual spring. Motor learning was assessed by comparing each partner's individual performance during trials in which they were not connected to the performance of participants who learned the task alone. We found that haptic interaction through a compliant spring does not lead to improved individual motor performance or an increase in motor learning rate. Performance during interaction was significantly better than when the partners were not interacting, even when connected to a worse partner.

Haptic human–human interaction does not improve individual visuomotor adaptation

“…Still, our data showed prominent yet similar individual improvement curves for all groups (see Fig. 2) and we found significant improvement of tracking error during interaction in the connected trials similar to Ganesh et al 3 and other studies using the same interaction paradigm [5][6][7] (Fig. 5).…”

“…Tracking performance improves during haptic interaction depending on the partner's relative single tracking performance. A common finding in similar haptic human-human interaction studies is that haptic interaction improves individual tracking error during interaction ( E c ) depending on the partner's relative tracking error in the subsequent single trial ( E p s ) 3,6,7,18 . Although our focus in this paper is on analysing single trial improvement, we also analysed E c versus E p s for the int.…”

“…Although the focus of this paper is on the effect of haptic interaction on individual motor improvement, we also analysed the tracking error improvement during interaction in the connected trials compared to the subsequent single trials (denoted by E c ) to check whether the haptic interaction paradigm yielded similar result as previous haptic human-human interaction studies work (specifically 3,6,7 ). The extent to which haptic interaction helps ( �E c > 0% ) or hinders ( �E c < 0% ) tracking performance depends on the partner's relative single performance E p s .…”

“…Reducing a participant's movement errors while they learn a new motor skill using robot-generated haptic assistance rarely transferred into improved subsequent individual performance compared to participants who received no haptic assistance [12][13][14][15][16] . Similarly, several studies on haptic human-human interaction consistently showed that tracking errors are significantly smaller during haptic interaction compared to performing the tracking task alone, particularly if you interact with a partner who is better than you 3,[5][6][7]9,10 . Combining these observations, we would expect little to no benefit of haptic human-human interaction on individual visuomotor adaptation.…”

“…Haptic interaction with an initially more skilled partner could facilitate a participant's individual improvement and improvement rates 26 . We analysed whether the difference in initial skill level between the partners impacted their individual improvement ( Lastly, previous work showed that a participant's tracking error in connected trials (E c ) depended on their partner's relative tracking error during the subsequent single trials 3,5,7 . To corroborate these results and check whether our interaction paradigm yields similar results, we calculated each participant's instantaneous improvement in tracking error during haptic interaction as �E c = (E s − E c )/E s , where E c is the tracking error in the connected trial and E s is the tracking error in the immediately following single trial.…”