Haptic Coupling to Negotiate Motion Plans

Haptic coupling is integral to everyday life, enabling humans to collaborate on tasks without the need for verbal agreement of every detail. However, collaborative partners often have differing plans and use haptic coupling to negotiate a common strategy. While previous studies have focused on tasks where partners share the same plan, little is known about haptic negotiation when plans diverge. This study investigates how the motion plans of two mechanically connected partners evolve during repeating a via-points arm-reaching task when they start from differing initial plans. In one group, partners had plans requiring similar effort, while in another group, plans were unbalanced, requiring different levels of effort. The analysis of shape and movement metrics shows that all dyads coordinated their plans through practice, influencing subsequent movements even when disconnected. For symmetric plans, partners exhibited slight mutual adaptation toward each other. In contrast, for asymmetric plans, the partner with the simpler plan tended to lead the movement, while the partner with the more complex plan complied and relaxed their plan. These findings suggest that, during collaboration, partners leverage mechanical interaction to simplify tasks and minimize effort.