haptic human human interaction - motor learning & haptic communication

Niek Beckers is PhD student in the Department of Biomechanical Engineering. His supervisor is prof.dr.ir. H. van der Kooij from the faculty of Engineering Technology (ET).

Haptic interaction with a partner – interaction by exerting forces onto each other directly or through an object – plays an important role in our lives. It can help us to coordinate our actions and it can benefit learning of new motor tasks; for example, a therapist can physically support a patient during recovery of their motor functions after injury or disease. My research goal is to create a better understanding of whether haptic interaction between two humans improves individual motor learning and why haptic interaction would improve motor performance.

We performed two experiments in which two partners learned novel motor tasks together: tracking a randomly-moving target in two novel environments. We haptically-connected the partners while they simultaneously learned a motor task. The partners were not made aware of the coupling. Although haptic interaction improved performance of both partners during interaction, this improvement was not retained when performing the task alone in both experiments. Hence, haptic interaction between humans does not improve individual motor learning in a collaborative motor task.

Interestingly, we found that haptic interaction improved motor performance during interaction, even when being coupled to a worse-performing partner. To explain this result, we developed a computational model of the interaction in which we mechanically coupled two simulated partners who both independently performed the same motor task. The model assumed that the partners were unaware of the haptic connection. Hence, the simulated partners were only mechanically influenced by the interaction force; they did not exchange any information about each other or the task through the interaction force to improve their performance. This model accurately predicted the improvement due to interaction observed in the experimental data. Additional model analysis suggested that haptic interaction improved performance because the compliant connection partially compensated for each partner's motor output variability, which includes tracking errors such as overshoots. The worse-performing partners additionally benefited from the haptic guidance provided by their better-performing partners. Similarly, we observed that partners did not coordinate reaching movements through the interaction force in another experiment.

In conclusion, our findings suggest that haptically-coupling two humans does not necessarily result in any exchange of information or motor coordination through the interaction force.