Attending to the preferred and to the non-preferred hand in complex bimanual task

Bruno Alleoni
Instituto de Bioci?ncias, UNESP - Rio Claro/SP

Ana Maria Pellegrini
Departamento de Educa??o F?sica, UNESP - Rio Claro/SP

Cynthia Hiraga
Faculdade de Artes, Ci?ncias e Humanidade, USP-Leste

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     Last modified: May 13, 2007

Abstract
Bimanual coordination is required to accomplish motor actions in many of our everyday tasks. In such bimanual actions, the two hands play quite different roles, whereas the non-dominant hand generally holds an object, the dominant hand acts upon it. Furthermore, the dominant hand leads the task and is more precise than the non-dominant hand. It has been argued that the superior performance of the dominant hand is due to the visual attention on the dominant hand. The aim of the present study was to examine the effect of directing visual attention to one of the hands during the performance of a bimanual task as a function of handedness and task complexity. Ten right- and eight left-handed adults participated in this study. The bimanual task required participants to tap continuously with two styluses on a transparent glass surface (i.e., a digitizing tablet). The tapping task required participants to tap on specific target areas (squares of 2x2 cm) according to a rhythm. The tapping conditions were: 1:1, 2:1, 3:1 and 3:2. The first and second digits refer to the number of targets aimed by the preferred hand and by the non-preferred hand, respectively. A metronome timed the first five seconds of the 20s trial. The direction of attention was: to the right hand, to the left hand and free. The dependent variables were the spatial and temporal errors. As expected, the results indicated that the easiest tasks (1:1 and 2:1) were performed with less spatial (F3,48 = 27,04, p< 0,05) and temporal (F3,48 = 32,30, p < 0,05) errors compared with that of more complex tasks (3:1 and 3:2). Right- and left-handed subjects showed similar level of spatial (F1,16 = 0,57, p > 0,05) and temporal errors (F1,16 = 1,11, p > 0,05). In terms of the spatial error, ANOVA showed significant difference in the interaction between Hand and Attention (F2,32 = 638,36, p < 0,05) and the Post-Hoc test showed that independently of hand, spatial errors for the non-attended hand were higher than that for the attended hand. Also independently of hand, there was no difference in spatial error between the attended preferred and non-preferred hand. In addition, the non-attended preferred hand showed higher error score compared with the non-attended non-preferred hand. In sum, the results for the present study showed that the preferred hand depends more on the allocation of visual attention than the non-preferred hand during bimanual coordination timed-tasks.