Human performance in three-hands tasks

A. Noccaro,J. Eden,D. Formica,E. Burdet,G. Di Pino

doi:10.1038/s41598-021-88862-9

A. Noccaro, J. Eden + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-88862-9

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Abstract

The successful completion of complex tasks like hanging a picture or laparoscopic surgery requires coordinated motion of more than two limbs. User-controlled supernumerary robotic limbs (SL) have been proposed to bypass the need for coordination with a partner in such tasks. However, neither the capability to control multiple limbs alone relative to collaborative control with partners, nor how that capability varies across different tasks, is well understood. In this work, we present an investigation of tasks requiring three-hands where the foot was used as an additional source of motor commands. We considered: (1) how does simultaneous control of three hands compare to a cooperating dyad; (2) how this relative performance was altered by the existence of constraints emanating from real or virtual physical connections (mechanical constraints) or from cognitive limits (cognitive constraints). It was found that a cooperating dyad outperformed a single user in all scenarios in terms of task score, path efficiency and motion smoothness. However, while the participants were able to reach more targets with increasing mechanical constraints/decreasing number of simultaneous goals, the relative difference in performance between a dyad and a participant performing trimanual activities decreased, suggesting further potential for SLs in this class of scenario.

Highlights

The successful completion of complex tasks like hanging a picture or laparoscopic surgery requires coordinated motion of more than two limbs
Previous studies which have evaluated the ability for a single human subject to coordinate three hands together include[12], who studied re-sizing[13,14], who demonstrated the ability to control three hands with the natural limb and[15] who investigated the impact of adding a third hand to different bi-manual tasks of varying coupling level
It can be seen that dyads perform better than solo subjects in term of score ( p < 0.001 ) and that their performance is significantly better in the 3-Coupled task when compared to both the uncoupled task ( p < 0.001 ) and 2-Coupled task ( p = 0.03 ) (Fig. 3a)

Summary

Introduction

The successful completion of complex tasks like hanging a picture or laparoscopic surgery requires coordinated motion of more than two limbs. Previous studies which have evaluated the ability for a single human subject to coordinate three hands together (trimanual activities) include[12], who studied re-sizing[13,14], who demonstrated the ability to control three hands with the natural limb and[15] who investigated the impact of adding a third hand to different bi-manual tasks of varying coupling level. From these studies it has been observed that human subjects can control three hands simultaneously. We investigated the questions of: (1) how do subjects perform in different trimanual tasks with different levels of virtual mechanical coupling and simultaneous targets to track? and (2) how does the subject’s performance compare to a dyad executing the same task? Using the subject’s dominant foot as an input for controlling a virtual third hand, thirty participants performed trimanual tasks in three scenarios: (1) uncoupled case, where each limb aims at a different goal and moves independently from the other limbs; (2) 2-coupled case, where two limbs have the same goal and are virtually mechanically coupled together while the third limb’s motion and goal are independent; (3) 3-coupled case, where all limbs have the same common goal and are virtually mechanically

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Conclusion