Right‐ and left‐hand skill II: Estimating the parameters of the distribution of L‐R differences in males and females

Abstract

The distribution of differences between the hands (L-R) in skill, as measured by a peg-moving task, was examined for several samples in which volunteer bias was absent or minimal. After comparing the main samples for hand preference and L-R times, they were combined to give 617 males and 863 females, aged 12-63 years. There was also a smaller sample of 122 males and 156 females, aged 6-15 years. The L-R distributions were negatively skewed and leptokurtotic. They were not compatible with the sum of two normal distributions, one of right-handers and one of left-handers. They were compatible with the sum of two or three normal distributions when one was unbiased to either side and the others were shifted to the right, as expected for the dominant or additive versions of the single gene interpretation of the right shift theory of handedness (Annett, 1978b, 1979). Sex differences in L-R scores confirmed that females tend to be more dextral than males. This was true of right-handers but not of left-handers, as expected if the sex difference is due to stronger expression of the rs+ gene in females than males and if this gene is absent in the majority of left-handers. There were trends suggesting that L-R asymmetry differs with educational status, undergraduates being less shifted toward dextrality than the general population.

Is left-handedness associated with a more pronounced age-related cognitive decline?

“…However, it should be noted that the cognitive abilities that were considered in the present study were mainly left hemispheric, which rises the question to what extent the results of the present study can be generalised to righthemispheric cognitive abilities. Some authors have indeed suggested that the effect of handedness on left and right hemispheric cognitive abilities is fundamentally different; i.e., that right-handed people have superior verbal skills due to non-optimal development of the left hemisphere (this hypothesis was not confirmed by the results of the present study), while left-handed people have superior visuospatial skills due to overdeveloped functioning of the right hemisphere (Annett & Kilshaw, 1983;Geschwind & Galaburda, 1987). In addition, it has also been suggested that ageing affects right hemispheric cognitive functions more strongly than left hemispheric cognitive functions (the right hemi-ageing hypothesis; Albert & Moss, 1988).…”

A gene-culture model of human handedness

“…The rare homozygote (rs--) is nondeterministically, or randomly, lateralized and, thus, equally likely to be right-or left-handed. In early versions of her model, she assumes complete dominance of the right-shift allele but later suggests an additive model (Annett and Kilshaw, 1983). Annett argues (i) that measures of handedness in performance tasks are continuously distributed in human and nonhuman vertebrate species, the variation resulting from unknown environmental factors; (ii) that these distributions are Gaussian in human and nonhuman vertebrate species and have the same standard deviations; and (iii) that the mean of the human distribution has been shifted from the symmetrical nonhuman position, where individuals are equally likely to be left-or right-handed, to the right, so that humans are predominantly righthanded.…”

Hora de balanço

“…41,58) . Em relação à consistência (intensidade) da preferência manual, existe uma incidência superior de ambidestralidade no sexo masculino (59) enquanto o sexo feminino revela maior tendência para intensificar o uso da mão preferida, no caso de esta ser a direita. De acordo com alguns autores (e.g.…”