Comparison of Solo and Collaborative Trimanual Operation of a Supernumerary Limb in Tasks With Varying Physical Coupling

Through the use of robotic supernumerary limbs, it has been proposed that a single user could perform tasks like surgery or industrial assembly that currently require a team. Although validation studies, often conducted in virtual reality, have demonstrated that individuals can learn to command supernumerary limbs, comparisons typically suggest that a team initially outperforms a supernumerary limb operating individual. In this study, we examined (i) the impact of using a commercially available physical robot setup instead of a virtual reality system and (ii) the effect of limb couplings on user performance during a series of trimanual operations. Contrary to previous findings, our results indicate no clear difference in user performance when working as a trimanual user, in the pick and place of three objects, compared to when working as a team. Additionally, for this task we observe that while users prefer working with a partner when they control most limbs, we find no clear difference in their preference between solo trimanual operation and when they work with a partner and control the third limb. These findings indicate that factors typically not present in virtual reality such as visual occlusion and haptic feedback may be vital to consider for the effective operation of supernumerary limbs, and provide initial evidence to support the viability of supernumerary limbs for a range of physical tasks.