title: Grasping others' movements: Rapid discrimination of object size from observed hand movements.
abstract: During reach-to-grasp movements, the hand is gradually molded to conform to the size and shape of the object to be grasped. Yet the ability to glean information about object properties by observing grasping movements is poorly understood. In this study, we capitalized on the effect of object size to investigate the ability to discriminate the size of an invisible object from movement kinematics. The study consisted of 2 phases. In the first action execution phase, to assess grip scaling, we recorded and analyzed reach-to-grasp movements performed toward differently sized objects. In the second action observation phase, video clips of the corresponding movements were presented to participants in a two-alternative forced-choice task. To probe discrimination performance over time, videos were edited to provide selective vision of different periods from 2 viewpoints. Separate analyses were conducted to determine how the participants' ability to discriminate between stimulus alternatives (Type I sensitivity) and their metacognitive ability to discriminate between correct and incorrect responses (Type II sensitivity) varied over time and viewpoint. We found that as early as 80 ms after movement onset, participants were able to discriminate object size from the observation of grasping movements delivered from the lateral viewpoint. For both viewpoints, information pickup closely matched the evolution of the hand's kinematics, reaching an almost perfect performance well before the fingers made contact with the object (60% of movement duration). These findings suggest that observers are able to decode object size from kinematic sources specified early on in the movement. (PsycINFO Database Record
authors.affiliation: Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
authors.forename: Caterina
authors.initials: C
authors.lastname: Ansuini
authors.affiliation: Department of Psychology, University of Torino.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavallo
authors.affiliation: Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
authors.forename: Atesh
authors.initials: A
authors.lastname: Koul
authors.affiliation: Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
authors.forename: Alessandro
authors.initials: A
authors.lastname: D'Ausilio
authors.affiliation: Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
authors.forename: Laura
authors.initials: L
authors.lastname: Taverna
authors.affiliation: Department of Robotics, Brain and Cognitive Sciences, Fondazione Istituto Italiano di Tecnologia.
authors.forename: Cristina
authors.identifier: 0000-0002-6845-0521
authors.initials: C
authors.lastname: Becchio
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D012858:Size Perception / Q000502:physiology*; D055815:Young Adult