A cross-cultural comparison of pressures to switch left-hand writing: Brazil versus Canada

Patterns of hand preference and unintentional injuries among Indian attempted hand switchers and hand non-switchers

This study examines the patterns of hand preference and unintentional injuries of attempted hand switchers and hand non-switchers. Data were collected from 3698 participants in Kharagpur, India, on measures of hand preference, hand switching, and unintentional injuries. The direction of left- or right-handedness was on the basis of hand used for the item "writing on paper" and the degree of handedness was based on the average score of remaining items in the handedness inventory. Results reveal that, among attempted hand-switchers, learned right-handers were not right-sided in hand continuum as the natural right-handers, but left-handers were left-sided as natural left-handers. With increasing age the learned right-handers become less right-sided and natural right-handers become more right-sided. Females (males) are found to be more right-handed than males (females) among learned right-handers (natural right-handers). On the direction of handedness, the learned right-handers have more than twice the risk of unintentional injuries than the natural right- and left-handers. On degree of handedness, the use of inconsistent left and both hands among natural left-handers, the use of inconsistent right and both hands among natural right-handers, and the use of weak right hand among learned right-handers increase their vulnerability to unintentional injuries. Any deviation from the genetic make-up in hand use elevates the risk of unintentional injuries, suggesting that one should not change the biological hand.

The cross-cultural nature of the relationship between schizotypy and mixed-handedness

Positive schizotypy is associated with non-right-handedness, which includes left- and mixed-handedness. However, because the underlying mechanisms might be different, it is important to examine whether both left- and mixed-handedness are associated with a high incidence of schizotypy. During 2009-2010, we used both the Perceptual Aberration Scale and Schizotypal Personality Questionnaire to assess 1315 undergraduate students in Taiwan for schizotypy and the Annett handedness questionnaire to assess handedness. Among the three-way classifications based on Annett's grouping, the fully left-handed group appeared to have the lowest score of positive schizotypy; next was the fully right-handed group and then the mixed-handed. Among the three-way classifications driven from cluster analysis, mixed-handers showed highest score of positive schizotypy. When handedness was treated continuously, both direction (e.g., Hand Preference Index) and consistency (e.g., Either hand use score) indicators were significantly correlated with schizotypy. The results of regression analyses showed that the quadratic handedness measure were negatively associated with schizotypy. The results remained similar after correcting for social pressure on left-handedness. In conclusion, the relationship between schizotypy and mixed-handedness appears to be cross-cultural. The dichotomous classification of handedness, right- vs. non-right-handedness, appears to be insufficient. Additional studies on the distinct mechanisms of mixed- and left-handedness are warranted.

On the origins of cultural differences in conformity: four tests of the pathogen prevalence hypothesis

What are the origins of cultural differences in conformity? The authors deduce the hypothesis that these cultural differences may reflect historical variability in the prevalence of disease-causing pathogens: Where pathogens were more prevalent, there were likely to emerge cultural norms promoting greater conformity. The authors conducted four tests of this hypothesis, using countries as units of analysis. Results support the pathogen prevalence hypothesis. Pathogen prevalence positively predicts cultural differences in effect sizes that emerge from behavioral conformity experiments (r=.49, n=17) and in the percentage of the population who prioritize obedience (r=.48, n=83). Pathogen prevalence also negatively predicted two indicators of tolerance for nonconformity: within-country dispositional variability (r=-.48, n=33) and the percentage of the population who are left-handed (r=-.73, n=20). Additional analyses address plausible alternative causal explanations. Discussion focuses on plausible underlying mechanisms (e.g., genetic, developmental, cognitive).

Handedness in Great Britain

Two large British databases of handedness assessed by writing hand at 10-11 years of age were analysed by geographical region. Left-handedness was found to vary significantly across regions according to one survey but not the other. In both data sets, left-handed writing was significantly more frequent in England than in Scotland and Wales combined. Possible reasons for this difference are discussed.