Sinistrality is associated with (slightly) lower general intelligence: A data synthesis and consideration of secular trend data in handedness

Publication date: Available online 12 June 2018Source: HOMOAuthor(s): Michael A. Woodley of Menie, Heitor B.F. Fernandes, Satoshi Kanazawa, Edward DuttonAbstractThe relationship between the general factor of intelligence (g) and handedness is investigated using a combined sample of 23511 respondents from three large databases: the NLSY’79 (US), NLSY’97 (US) and NCDS (UK). Dextrals – those who use their right hands were found to be 1.22 IQ points higher than sinistrals (left handers) after controling for sex and age and correcting for sources of measurement error. To see if the association between IQ and handedness was strongest on the abilities that were the best measures of g, the method of correlated vectors was used to test for moderation. Across the three studies, g was found to very weakly negatively moderate the association between ability measure and handedness (ρ=-.023, K=3, N=23511), however in the NLSY’79, the coding speed subtest was an outlier in terms of the strength of its association with handedness. Its removal yielded indications of positive moderation in this dataset, which when aggregated boosted the overall vector correlation value to .539 (K=3, N=23511), suggesting that g might be an important moderator of this relationship. Secondary analysis of secular trend data on the changing percentage of sinistrals in Western populations indicates that overall, sinistrality has increased, entailing a g decline of .106 points over 150 years (.006 points per...
Source: HOMO Journal of Comparative Human Biology - Category: Biology Source Type: research