En ook de link met een asymmetrie van het lichaam of lateralisatie wordt gelegd (verschillen tussen de linker en de rechter hersenhelft). Hoe meer asymmetrie tussen beide hersenhelften, hoe minder links- rechts verwarring:
It has been proposed that the labels left and right are applied to a “continuous asymmetric pattern of sensory excitation from the muscles and joints between the two sides of the body”, and that this somesthetic difference “provides a left-right gradient (...) which forms the basis for the intuitive awareness of a difference between the sides which most (but not all) normal persons possess (and this difference is) often verbalized in terms of the right side being felt as larger, heavier, and stronger than the left”. Also according to these authors the establishment of unilateral manual preference is regarded as a key element in the development of this gradient.
... If the assumption of such a passive sensory asymmetry is true, then it follows that individuals who perceive a stronger asymmetry between the left and right sides of their bodies should possess a stronger intuitive awareness of the left-right concept, and hence demonstrate less left-right confusion....
As left handed and ambidextrous individuals were believed to have less asymmetric brain functions than right handers, performance on left-right decision tasks was compared between groups of different handedness. This variable produced no significant effects in the RT task.
Similar negative results were obtained by comparing left-handed and right-handed (as determined by a set of hand efficiency tests) 10-year-old boys on a left-right discrimination task [19]. Probably, left or right handedness as such is not a good criterion to distinguish more from less lateralized individuals. Not the side of handedness appears important but the degree, and this observation fits with the asymmetry hypothesis.
In addition to handedness, increased somesthetic asymmetry is negatively correlated with left-right confusion. To the best of our knowledge, this finding has not been reported before, but again fits with the asymmetry hypothesis.
Met vooral een interessant besluit van de studie:
We conclude that individuals with more pronounced asymmetries regarding handedness and tactile sensitivity are able to give faster responses on a timed left-right discrimination task suggesting that they have less problems with left-right discrimination which is confirmed by these individuals’ self-reports on left-right confusion. This finding is in agreement with the asymmetry hypothesis which states that humans solve the left-right distinction problem of symmetrical beings by using a left-right response bias to distinguish between both sides of a horizontal dimension. Making asymmetrical responses due to handedness or reliance on an asymmetric pattern of bodily awareness could be methods to create such a bias. From this hypothesis, we predicted that given the substantial individual variability in both the degree of handedness and the degree of left-right confusion, stronger hand laterality would give rise to less difficulties with left-right discrimination. This prediction was empirically confirmed. Similar findings were obtained for asymmetries in tactile sensitivity. Although the association between bodily asymmetries and left-right confusion is significant, the relation is rather weak, suggesting that there must be other factors involved...
uit: Vingerhoets, Sarrechia, Individual differences in degree of handedness and somesthetic asymmetry predict individual differences in left-right confusion, Behavioural Brain Research 204 (2009) 212–216
En een andere studie:
...because left- and mixed-handers are thought to be less lateralised (Hellige, 1993). The decision to compare men with women was partly driven by the very inconsistent findings regarding handedness and LRC.
... found lefthanders to be more affected by LRC than right-handers, while Jordan et al. (2006) and Bakan and Putnam (1974) found no differences. Snyder (1991) even found no difference in accuracy but reported that left-handers responded faster to left– right decisions than right-handers. These contradictory results might have emerged because LRC was based only on self-reports instead of experimental studies. The present study has demonstrated that in addition to simply comparing supposedly more and less lateralised participants (such as left- or right-handers), it is important directly to measure the degree of (language) lateralisation. However, it would be interesting to compare left- with right-handers, if behavioural LRC tasks are used and hemispheric asymmetries are assessed experimentally.
uit: Hirnstein, Ocklenburg, et all, Research report: Sex differences in left–right confusion depend on hemispheric asymmetry, cortex 45 (2009) 891–899
De 2 studies zijn jammer genoeg enkel te bekijken
online als abstract.
En deze aanvulling geeft kort hetzelfde weer:
...All other species, except perhaps chimpanzees, are made up half and half of right handers and left handers. Nor is it coincidence that humans alone have language, and that language is mostly located in the left hemisphere, which controls the right hand. The left hemisphere processes information more quickly than the right hemisphere. This speed is required both for online processing of grammar and the rapid movements needed in speech and fine motor skills.
It is less surprising that left and right are confused than that they can be distinguished at all, and that ability also seems to be unique to humans. The physicist Ernst Mach showed that true right-left discrimination, the association of arbitrary stimuli to right or left sides, requires a system that is itself asymmetric. Because men’s brains are somewhat more asymmetric than women’s brains, and right handed people’s brains are more asymmetric than left handed people’s brains, right-left confusion is more prevalent in women and left-handed people....
uit:
BMJ 2008;337:a2906
Blijkbaar is het dus allemaal nog niet zo duidelijk vanwaar de links- rechts verwarring komt.
Dido
Ik ben niet jong genoeg om alles te weten...
-Oscar Wilde-