Academic journal article International Journal of Psychological Studies

Hemispatial Effects for Left- and Right-Handers on a Pointing Task

Academic journal article International Journal of Psychological Studies

Hemispatial Effects for Left- and Right-Handers on a Pointing Task

Article excerpt

Abstract

The primary goal of the current study was to determine if left-handers show an advantage for each hand in its own region of space, as do right-handers. Additionally, the study aimed to determine whether a preferred-hand advantage for movement exists in a highly-practiced task. To examine these questions, 81 right- and 60 left-handers were administered the Waterloo Handedness Questionnaire (WHQ) and completed a computer-based pointing action, where kinematic data was recorded. Here, participants were required to move to a target, located to left, midline and right of the starting position, maximizing both speed and accuracy. A 3-target location (left, midline and right space) by two hand (left, right) repeated measures ANOVA was performed for each kinematic variable, for each handedness group separately. Results indicated that left-handers showed the same spatial compatibility or object proximity effect noted by other researchers in right-handers. However, no preferred-hand advantage was found, replicating the work of Bryden and Roy (1999) who showed that the existence of the preferred-hand advantage is dependent upon the degree of spatial precision required at the movement goal.

Keywords: handedness, preferred-hand advantage, pointing task

1. Introduction

Differences in the processes of hemispatial effects underlying reaching movements ipsilateral and contralateral to the midline of the body have been thoroughly investigated in the literature. Research suggests movements made by the arm ipsilateral to the target demonstrates numerous advantages (including shorter reaction and movement time, and greater accuracy) in comparison to movements made by the arm contralateral to the target. Such advantages are thought to be based on intrahemispheric transmission of visual information from an ipsilateral target within the same hemisphere as the motor cortices in control of the moving limb (Carey, Hargreaves & Goodale, 1996; Carey & Otto-de Haart, 2001).

Biomechanical factors have also been implicated in hemispatial effects (Gordon, Gilhardi, Cooper & Ghez, 1994; Carey et al., 1996; Carey & Otto-de Haart, 2001; Barthélémy & Boulinguez, 2002); demonstrating how differences in inertial forces can be used to explain kinematic differences when comparing ipsilateral and contralateral movements (Gordon et al., 1994). Additionally, hemispatial advantages have been linked to the location of the motor response direction, as opposed to the location of the target (Carey et al., 1996). More recent investigations (Carey and Otto-de Haart, 2001) have not confirmed the arguments of Carey et al. (1996) and Gordon et al. (1994), where Barthélémy and Boulinguez (2002) have suggested that biomechanical factors are unable to account for hemispatial effects on reaction time; therefore the within- versus between-hemisphere model best accounts for these differences. Overall, it may be suggested that a combination of biomechanical and hemispatial effects contribute to the advantages noted in movements toward ipsilateral targets.

Generally speaking, goal-directed movements are thought to involve the cerebral hemisphere, which controls the hand used to perform the task. Additionally, it is thought that the two hemispheres are specialized for different types of information processing (Bradshaw, Bradshaw & Nettleton, 1990; Goodale, 1988) and that these differences ultimately lead to the observed performance differences between the hands. The body of literature on goal-directed movements has shown two types of motor asymmetries in right-handers. First, shorter reaction times for the lefthand movements have been found (Haaland & Harrington, 1989; Carson, Chua, Elliott & Goodman, 1990; Velay & Benoit-Dubrocard, 1999; Boulinguez, Nougier & Velay, 2001a,b; Velay, Daffaure, Raphael, & Benoit-Dubrocard, 2001), which are thought to be suggestive of a right hemispheric specialization for movement preparation and/or spatial processing. …

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