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

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 optima...

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Bibliographic Details
Published in:PloS one 2015-05, Vol.10 (5), p.e0128322-e0128322
Main Authors: Raw, Rachael K, Wilkie, Richard M, White, Alan, Williams, Justin H G, Mon-Williams, Mark
Format: Article
Language:English
Subjects:
Adolescent
Adult
Adults
Age
Age differences
Aging
Analysis
Asymmetry
Autism
Evidence-based medicine
Female
Handwriting
Health aspects
Hemispheric laterality
Humans
Learning
Learning theory
Male
Measurement
Medical care
Models, Biological
Nervous system
Neurophysiology
Older people
Studies
United States
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Summary: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).
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0128322