| Summary: | This thesis explores differences in response style between left- and right-handed individuals. Evolutionary and comparative backgrounds suggest that we should expect left- and right-handers to show differential responses in some similar situations and for the behaviour of left-handers to be adaptive and not necessarily pathological. Exploration of genetics, pathology and culture show that hand preference is best understood in terms of a genetic susceptibility modulated by experience. Consideration of how to measure and categorise handedness revealed that there is no universally accepted method and so a new inventory was developed, utilising the main accepted measuring scales (Annett, 1970; Oldfield, 1971 and Peters, 1998). A series of experiments was conducted in order to explore the potential differences in response style. Chapter 4 looked at response to a novel task: the 3-disk Tower of Hanoi and found that left-handers took significantly longer to start the task and solved it in significantly fewer moves than right-handers. In Chapter 5, the role of emotional processing was explored and it was found that both left- and right-handers showed broadly similar identification of facial emotions, although there were some sex and valence effects. This suggests that the differences in response style were probably not caused by differential lateralised emotional processing (and negative emotional 'interference') differences. Chapter 6 investigated the role of planning and type of task and found that in common with the findings of Chapter 4 when completing a manual sorting task there was a handedness effect, with right-handers showing a significantly quicker latency to start the task. However, spatial tasks showed mixed effects and sequencing tasks showed no significant differences. It was hypothesised that novelty of task might be the cause and this was further explored in Chapter 7. This chapter looked at the influence of stress and anxiety as well as the role of novelty. A further study using the Tower of Hanoi showed a similar but non-significant first move difference on a 'simple' version (3-disk) of the task but not the more complex (4-disk) version. However, state anxiety (Speilberger, 1983) was found to be significantly higher for left-handers on the simple task (when it was novel) but not for the 4-disk and non-novel versions. This suggests that task complexity and novelty may be important factors in understanding differences in response style between left- and right-handers. These findings are discussed in terms of the literature and suggestions are made for future studies.
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