| Summary: | This thesis examined asymmetries during bimanual coordination, investigating proposals that attention is biased toward the right hand of right-handers (Peters, 1981). To this end, several new tasks designed to elicit this attentional asymmetry were developed. The first series of experiments (Chapter 2) utilised a discontinuous double-step reaching task, where the refractory period between bimanual and unimanual states was used to infer the direction of attention. A shorter right hand refractory period was found in the majority of these experiments, supporting the proposed attentional bias. Furthermore, altering the direction of attention during the task shifted the asymmetry in a way consistent with the attentional bias hypothesis. The third chapter examined the possibility of a related bias toward selecting the right hand. In a similar double-step task, one hand was validly or invalidly-cued to make the unimanual portion of the reach. The asymmetries in error levels and refractory period scores on the invalidly-cued trials suggested that the right hand was ‘primed’ to move following bimanual coordination. The fourth chapter’s experiments required participants to reach with both hands to either the right or left sides of space, to determine which hand was yoked to which. Although the right hand appeared to be ‘in-charge’ in terms of movement duration, the coupling appeared to favour the left hand for movement onset. The fifth chapter combined a common rhythmic coodination task with a ‘mirror illusion’, such that a virtual hand was seen in place of its counterpart. This experiment investigated which hand was more readily influenced by the visual illusion, however the bimanual coordination was unaffected by the mirror’s orientation (i.e., if the left or right hand was reflected).
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