title: Task difficulty and inertial properties of hand-held tools: An assessment of their concurrent effects on precision aiming.
abstract: Aiming hand-held tools at targets in space entails adjustments in the dynamical organization of aiming patterns according to the required precision. We asked whether and how these adjustments are modified by the tool's mass distribution. Twelve participants performed reciprocal aiming movements with a 50-cm long wooden probe. Kinematic patterns of probe movements were used as a window into the behavioral dynamic underlying performance of a reciprocal aiming task. We crossed three levels of task difficulty (IDs 2.8, 4.5 and 6.1) with two types of probe varying in their mass distribution (proximal vs distal loading). Movement duration was affected by task difficulty and probe loading (shorter for larger targets and proximal probe loading). Progressive deviations from a sinusoidal movement pattern were observed as task difficulty increased. Such deviations were more pronounced with proximal probe loading. Results point to a higher degree of non-linearity in aiming dynamics when the probe was loaded proximally, which might reflect employment of additional perceptual-motor processes to control the position of its less stable tip at the vicinity of the targets. More generally, the effects of probe loading on aiming pattern and dynamics suggest that perceptual-motor processes responding to task level constraints are sensitive to, and not independent from, biomechanical, end-effector constraints.
authors.affiliation: Graduate Program in Rehabilitation Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Campus Pampulha, Belo Horizonte, MG 31270-010, Brazil; Department of Psychology, University of Cincinnati, 4150N Edwards 1 Bldg, P.O. Box 210376, Cincinnati, OH 45221-0376, United States. Electronic address: paula.silva@uc.edu.
authors.forename: Paula L
authors.initials: PL
authors.lastname: Silva
authors.affiliation: Institut des Sciences du Mouvement - UMR 7287, Aix-Marseille Université, Marseille, France.
authors.forename: Reinoud J
authors.initials: RJ
authors.lastname: Bootsma
authors.affiliation: Graduate Program in Rehabilitation Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Priscilla Rezende Pereira
authors.initials: PR
authors.lastname: Figueiredo
authors.affiliation: Graduate Program in Rehabilitation Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Bruna Silva
authors.initials: BS
authors.lastname: Avelar
authors.affiliation: Graduate Program in Sports Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: André Gustavo Pereira
authors.initials: AG
authors.lastname: de Andrade
authors.affiliation: Graduate Program in Rehabilitation Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Sérgio T
authors.initials: ST
authors.lastname: Fonseca
authors.affiliation: Graduate Program in Rehabilitation Science, School of Physical Education, Physical Therapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Marisa Cotta
authors.initials: MC
authors.lastname: Mancini
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time; D055815:Young Adult
keywords: Fitts’ task; Kinematics; Long-shafted probe; Mass distribution; Reciprocal aiming