Communication and Inference of Intended Movement Direction during Human–Human Physical Interaction

Abstract

Of particular interest to the neuroscience and robotics communities is the understanding of how two humans could physically collaborate to perform motor tasks such as holding a tool or moving it across locations. When two humans physically interact with each other, sensory consequences and motor outcomes are not entirely predictable as they also depend on the other agent’s actions. The sensory mechanisms involved in physical interactions are not well understood. The present study was designed (1) to quantify human–human physical interactions where one agent (“follower”) has to infer the intended or imagined—but not executed—direction of motion of another agent (“leader”) and (2) to reveal the underlying strategies used by the dyad. This study also aimed at verifying the extent to which visual feedback (VF) is necessary for communicating intended movement direction. We found that the control of leader on the relationship between force and motion was a critical factor in conveying his/her intended movement direction to the follower regardless of VF of the grasped handle or the arms. Interestingly, the dyad’s ability to communicate and infer movement direction with significant accuracy improved (>83%) after a relatively short amount of practice. These results indicate that the relationship between force and motion (interpreting as arm impedance modulation) may represent an important means for communicating intended movement direction between biological agents, as indicated by the modulation of this relationship to intended direction. Ongoing work is investigating the application of the present findings to optimize communication of high-level movement goals during physical interactions between biological and non-biological agents.

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact

“…Side-by-side walking with hand contact is a common situation that we naturally experience since infancy. The relationship between force and motion represents an important means for communicating between biological agents (Rosenbaum et al, 2006 ; van der Wel et al, 2011 ; Ganesh et al, 2014 ; Roelofsen et al, 2016 ; Lanini et al, 2017 ; Mojtahedi et al, 2017 ; Sawers et al, 2017 ). The developed approach and metrics to assess the sensory and motor mechanisms underlying human-human interaction, and the directional forces and their variability in particular, can be used to successfully identify interactions during various locomotor tasks, such as haptic guidance during dimensional locomotion, unstable walking, etc.…”

Muscle synergies and activation in Nordic walking compared with conventional walking

“…Indeed, the average gait speed increase for patients in the experimental group was 0.1 m/s, compared to an increase of 0.03 m/s for the control group. The reported minimal clinically meaningful change for post-acute stroke patients in literature is 0.06 m/s [4], a value reasonably greater than the one for chronic patients. At the moment, we cannot exclude that the larger increase of gait speed in the experimental group may be partially due to the overall small sample size and the lower gait speed shown by the experimental group at T1, compared to the control one.…”

“…Relatively small interaction forces may communicate movement goals during cooperative physical interactions [3]. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions [3][4][5], as well as they were not quantified for walking. Such studies may also provide insights into the role of interaction forces in the dyad's ability to communicate and interpret intended motion during locomotion.…”

On the Role of Physical Interaction on Performance of Object Manipulation by Dyads

“…Joint actions from two randomly-paired individuals could potentially induce environmental uncertainty. Specifically, when two brains are controlling effectors (one upper limb each), it is expected that either brain cannot fully predict the action of the other (Mojtahedi et al, 2017 ). Therefore, each individual may treat the motor output on the other handle as partially environmental noise or uncertainty.…”