Search

A recent article in the "Journal of Deaf Studies and Deaf Education" (Leigh, Brice, & Meadow-Orlans, 2004) explored attachment between deaf mothers and their 18-month-old children and reported relationship patterns similar to those for hearing dyads. The study reported here explores a marker of early mother-child relationships: cradling laterality. Results indicated that, overall, the cradling bias of deaf mothers is similar to that of hearing mothers, but that there are significant differences among deaf mothers related to the hearing status of their own parents and, in a complex way, to the hearing status of their children. Deaf mothers of deaf parents showed a strong leftward cradling bias with both hearing and deaf children, whereas deaf mothers of hearing parents showed a leftward cradling bias with hearing children and a rightward cradling bias with deaf children. Possible explanations for these patterns of behavior are discussed.

Human studies consistently report a 60%–80% maternal left cradling preference. The dominant explanation points to an engagement of the emotionally more-attuned right brain. In contrast, we found equal incidences of left (31.3%), right (34.3%) and no-preference (34.3%) cradling in an impoverished South African population living under adverse conditions characterized by extreme dangers. We found striking differences on the Parenting Stress Index (PSI) between mothers with no cradling laterality preference and mothers with either a left or right preference. In several mammals a homologous left preference becomes stronger when acute threats prevail, rendering the rightwards shift we observed under dangerous conditions seemingly paradoxical. We propose this paradox can be resolved in terms of life-history strategy theory which predicts reduced parental investment in chronically dangerous environments. We interpret our high PSI score findings in no-preference cradlers as indicative of poorer, or at least ambivalent, maternal coping which many studies show is typically associated with reduced emotional sensitivity and responsiveness. We suggest that the latter may be a psychological mechanism mediating a partial withdrawal of parental investment in response to an enduringly adverse environment. To the best of our knowledge, this is the first study investigating cradling laterality preferences in an adverse socioeconomic environment. [ABSTRACT FROM AUTHOR]

We describe a possible link between coordinated laterised group behaviour serving species survived in lower vertebrates and a striking lateralisation phenomenon found in human social behaviour: the universal preference for cradling a young infant on the left side. Our exploration offers a different perspective on the role of cerebral asymmetry for the survival of both the individual and the species.

This commentary supports MacNeilage's dismissal of an evolutionary development from sign language to spoken language but presents evidence of a feature in sign language (echo phonology) that links iconic signs to abstract vocal syllables. These data provide an insight into possible mechanism by which iconic manual gestures accompanied by vocalisation could have provided a route for the evolution of spoken language with its characteristically arbitrary form-meaning relationship.

Although gestures have surface similarities with language, there are significant organisational and neurolinguistic differences that argue against the evolutionary connection proposed by Corballis. Dominance for language and handedness may be related to a basic specialisation of the left cerebral hemisphere for target-directed behaviour and sequential processing, with the right side specialised for holistic-environmental monitoring and spatial processing.