Olga Vasileva, Senay Cebioglu and Tanya Broesch
A number of studies investigating development of handedness and communication suggest that the two traits are not independent in human evolution and ontogeny (Cochet & Byrne, 2013); such an association remains an expectation in the field (Fagard, Spelke & von Hofsten, 2009).
There is evidence suggesting a relationship between handedness (hand preference in object manipulation) and language development with some studies reporting early handedness to be a predictor for future language development (Gonzales et al. 2015; Nelson, Campbell & Michel, 2014). Similarly, studies by Vauclair & Imbault, (2009) and Cochet & Vauclair (2010) suggest that children who tend to point with a right-hand advance in language development. Importantly, co-development of hand preference for object manipulation and gesture along with language is consistent with gestural origins of language in humans (Cochet, 2013).
A possible explanation for abovementioned results is that early communication and handedness are bounded by the developmental context. Both handedness in object manipulation and gesture co-develop in ontogeny due to what Vauclair (2003) calls a “human typical” scenario. In such a scenario a caregiver engages in object manipulation with a child, simultaneously labeling objects (verbal language), thus allowing a child extensive interaction with an object that is coupled with rich verbal communication. Gestural communication is also profound, and the child is using the right hand more and more during both instances (grasping-object manipulation and gesture usage). Thus, the right-hand preference so typical for humans develops in both domains: communicative and motor one. Following such a scenario, similar co-developmental process could take place in human evolution, where language (and its asymmetry) and handedness co-evolved due to their joint context.
However, such “human-typical” developmental context has been proposed based on research conducted with WEIRD (Western, Educated, Industrial, Rich and Democratic) cultures (Henrich et al., 2010; Nielsen & Haun, 2016). Little is known about development of handedness and gesture in non-industrial societies, where the developmental context of these traits might differ from the one in an industrial society. To test whether a “human-typical” scenario would hold in a non-WEIRD society, we investigated hand preference in object manipulation and pointing gesture (2 tasks each) in 15 to 30-months-old children in two distinct sociocultural contexts: urban Canada (n = 30) and rural Vanuatu (n = 30), a small-scale island society located in South Pacific.
The results from the Canadian sample replicate previous research in WEIRD samples, with significant association between hand preference and pointing gesture. However, in the Vanuatu sample, there was no association between hand preference and pointing. Moreover, children in Vanuatu were more strongly right-handed for the communicative gesture, than children in Canada. We suggest that in children who experience more verbal interaction with a caregiver during object manipulation and play, gestural and motor asymmetries are not independent. On the contrary, in some cultures handedness and gestural communication develop in a more independent manner. Result of the study point to the importance of considering the context of handedness and communicative relationship in the course of human evolution.
References
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Cochet H., Byrne RW. (2013) Evolutionary origins of human handedness: evaluating contrasting hypotheses. Animal Cognition, 16(4), 531-42.
Fagard, J., Spelke, E., & von Hofsten, C. (2009). Reaching and grasping a moving object in 6-, 8-, and 10-month-old infants: Laterality and performance. Infant Behavior and Development, 32(2), 137-146.
Gonzalez, S. L., Nelson, E. L., Campbell, J. M., Marcinowski, E. C., Coxe, S., & Michel, G. F. (2015). 18-24 months handedness predicts 36 months expressive language skills. Dev. Psychobiology, 57, S16.
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Nielsen, M., & Haun, D. (2016). Why developmental psychology is incomplete without comparative and cross-cultural perspectives. Philosophical Transactions of the Royal Society B: Biological Sciences.
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Vauclair, J., & Imbault, J. (2009). Relationship between manual preferences for object manipulation and pointing gestures in infants and toddlers. Developmental science, 12(6), 1060-1069.