title: The Change in Fingertip Contact Area as a Novel Proprioceptive Cue.
abstract: Humans, many animals, and certain robotic hands have deformable fingertip pads [1, 2]. Deformable pads have the advantage of conforming to the objects that are being touched, ensuring a stable grasp for a large range of forces and shapes. Pad deformations change with finger displacements during touch. Pushing a finger against an external surface typically provokes an increase of the gross contact area [3], potentially providing a relative motion cue, a situation comparable to looming in vision [4]. The rate of increase of the area of contact also depends on the compliance of the object [5]. Because objects normally do not suddenly change compliance, participants may interpret an artificially induced variation in compliance, which coincides with a change in the gross contact area, as a change in finger displacement, and consequently they may misestimate their finger's position relative to the touched object. To test this, we asked participants to compare the perceived displacements of their finger while contacting an object varying pseudo-randomly in compliance from trial to trial. Results indicate a bias in the perception of finger displacement induced by the change in compliance, hence in contact area, indicating that participants interpreted the altered cutaneous input as a cue to proprioception. This situation highlights the capacity of the brain to take advantage of knowledge of the mechanical properties of the body and of the external environment.
authors.affiliation: Department of Cognitive Neuroscience, Universität Bielefeld, 33615 Bielefeld, Germany; Cognitive Interaction Technology Centre of Excellence, Universität Bielefeld, 33615 Bielefeld, Germany; Department of Systems Medicine and Centre of Space Bio-Medicine, Università di Roma "Tor Vergata," 00173 Rome, Italy. Electronic address: alessandro.moscatelli@uni-bielefeld.de.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moscatelli
authors.affiliation: Advanced Robotics Department, Istituto Italiano di Tecnologia, 16163 Genova, Italy; Università di Pisa, Centro di Ricerca E. Piaggio, 56122 Pisa, Italy. Electronic address: matteo.bianchi@centropiaggio.unipi.it.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bianchi
authors.affiliation: Università di Pisa, Centro di Ricerca E. Piaggio, 56122 Pisa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Serio
authors.affiliation: Laboratoire de Psychologie de la Perception, CNRS and Université Paris Descartes, 75006 Paris, France; Sorbonne Universités, UPMC Université Paris 06, UMR 7222, ISIR, 75005 Paris, France.
authors.forename: Alexander
authors.initials: A
authors.lastname: Terekhov
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR 7222, ISIR, 75005 Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Hayward
authors.affiliation: Department of Cognitive Neuroscience, Universität Bielefeld, 33615 Bielefeld, Germany; Cognitive Interaction Technology Centre of Excellence, Universität Bielefeld, 33615 Bielefeld, Germany; Applied Cognitive Psychology, Ulm University, 89081 Ulm, Germany.
authors.forename: Marc O
authors.initials: MO
authors.lastname: Ernst
authors.affiliation: Advanced Robotics Department, Istituto Italiano di Tecnologia, 16163 Genova, Italy; Università di Pisa, Centro di Ricerca E. Piaggio, 56122 Pisa, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bicchi
mesh_terms: D000328:Adult; D005246:Feedback; D005260:Female; D005385:Fingers / Q000294:innervation*; D006801:Humans; D008297:Male; D008465:Mechanoreceptors; D011434:Proprioception / Q000502:physiology*; D014110:Touch / Q000502:physiology; D014796:Visual Perception; D055815:Young Adult