The 'Goldilocks Zone': getting the measure of manual asymmetries

Rachael K Raw, Richard M Wilkie, Alan White, Justin H G Williams, Mark Mon-Williams

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4 Citations (Scopus)
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Some studies have shown that manual asymmetries decrease in older age. These results have often been explained with reference to models of reduced hemispheric specialisation. An alternative explanation, however, is that hand differences are subtle, and capturing them requires tasks that yield optimal performance with both hands. Whereas the hemispheric specialisation account implies that reduced manual asymmetries should be reliably observed in older adults, the 'measurement difficulty' account suggests that manual asymmetries will be hard to detect unless a task has just the right level of difficulty--i.e. within the 'Goldilocks Zone', where it is not too easy or too hard, but just right. Experiment One tested this hypothesis and found that manual asymmetries were only detected when participants performed in this zone; specifically, performance on a tracing task was only superior in the preferred hand when task constraints were high (i.e. fast speed tracing). Experiment Two used three different tasks to examine age differences in manual asymmetries; one task produced no asymmetries, whilst two tasks revealed asymmetries in both younger and older groups (with poorer overall performance in the old group across all tasks). Experiment Three revealed task-dependent asymmetries in both age groups, but highlighted further detection difficulties linked with the metric of performance and compensatory strategies used by participants. Results are discussed with reference to structural learning theory, whereby we suggest that the processes of inter-manual transfer lead to relatively small performance differences between the hands (despite a strong phenomenological sense of performance disparities).

Original languageEnglish
Article number0128322
Number of pages20
JournalPloS ONE
Issue number5
Early online date29 May 2015
Publication statusPublished - 29 May 2015

Bibliographical note

Data was collected by Rachael Raw who was funded by an Medical Research Council (MRC) CASE PhD studentship in collaboration with The Magstim Company Ltd. Analysis and publication was supported by an MRC Centenary Early Career Post-Doctoral Fellowship awarded to Rachael Raw. We would like to thank Ian Flatters and Liam Hill for their assistance with recruitment and data collection.


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