title: In a demanding task, three-handed manipulation is preferred to two-handed manipulation.
abstract: Equipped with a third hand under their direct control, surgeons may be able to perform certain surgical interventions alone; this would reduce the need for a human assistant and related coordination difficulties. However, does human performance improve with three hands compared to two hands? To evaluate this possibility, we carried out a behavioural study on the performance of naive adults catching objects with three virtual hands controlled by their two hands and right foot. The subjects could successfully control the virtual hands in a few trials. With this control strategy, the workspace of the hands was inversely correlated with the task velocity. The comparison of performance between the three and two hands control revealed no significant difference of success in catching falling objects and in average effort during the tasks. Subjects preferred the three handed control strategy, found it easier, with less physical and mental burden. Although the coordination of the foot with the natural hands increased trial after trial, about two minutes of practice was not sufficient to develop a sense of ownership towards the third arm.
authors.affiliation: Robotic Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Elahe
authors.initials: E
authors.lastname: Abdi
authors.affiliation: Department of Bioengineering, Imperial College of Science, Technology and Medicine, London, United Kingdom.
authors.forename: Etienne
authors.initials: E
authors.lastname: Burdet
authors.affiliation: Robotic Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bouri
authors.affiliation: Pediatric General and Thoracic Surgery, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sharifa
authors.initials: S
authors.lastname: Himidan
authors.affiliation: Robotic Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Hannes
authors.initials: H
authors.lastname: Bleuler
mesh_terms: D000328:Adult; D005260:Female; D005716:Game Theory; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D013647:Task Performance and Analysis; D055815:Young Adult