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Wenxun Li, Leonard Matin; Bimanual Interaction in Pointing to a Common Visual Target with Unseen Hands. Journal of Vision 2010;10(7):1071. doi: 10.1167/10.7.1071.
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© ARVO (1962-2015); The Authors (2016-present)
Although bimanual performance generally involves high correlation between the responses of the two hands, bimanual independence has been achieved by haptic tracking two different targets, indicating that people can maintain two separate movement plans simultaneously. Recently, we found that observers maintained a high degree of bimanual independence when manual heightmatching to a common visual target. In the present experiments, we employed bimanual pointing to a common visual target. Observers in darkness monocularly viewed a visual target either 12o above, 12o below, or at eye level with a 50o-long inducing line pitched either -30o (topbackward), or 20o (topforward) at 25o horizontal eccentricity. Manual pointing to the target was measured by a Polhemus 3-Space search coil with the unseen hand either in the midfrontal plane or with a fully-extended arm. The perceived elevation of a fixed-height target was raised in a pitched-topbackward visual field and lowered in a pitched-topforward visual field. However, manual pointing to the mislocalized target was accurate with the fully-extended arm whereas, with the hand in the midfrontal plane, pointing errors were equal and opposite to the perceptual mislocalization. With the hands at different distances simultaneously, the pointing direction to the target by the second hand was influenced by the prior pointing direction of the first hand. Average bimanual transfer approximated 43%, whether the first pointing was with the left or right hand. Less transfer (bimanual independence) was found with the first hand pointing from the midfrontal plane and the second hand pointing with a fully-extended arm than for the reverse order of manual distances. Similar results were obtained for different target heights. Hand dominance also played an important role: 65% transfer was measured for the dominant to the nondominant hand, 24% transfer was measured for the nondominant hand to the dominant hand.
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