Cerebral asymmetry: From survival strategies to social behaviour

We describe a possible link between coordinated lateralised group behaviour serving species survival 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

Visual Laterality of Calf–Mother Interactions in Wild Whales

Behavioral laterality is known for a variety of vertebrate and invertebrate animals. Laterality in social interactions has been described for a wide range of species including humans. Although evidence and theoretical predictions indicate that in social species the degree of population level laterality is greater than in solitary ones, the origin of these unilateral biases is not fully understood. It is especially poorly studied in the wild animals. Little is known about the role, which laterality in social interactions plays in natural populations. A number of brain characteristics make cetaceans most suitable for investigation of lateralization in social contacts.) in the greatest breeding aggregation in the White Sea. Here we show that young calves (in 29 individually identified and in over a hundred of individually not recognized mother-calf pairs) swim and rest significantly longer on a mother's right side. Further observations along with the data from other cetaceans indicate that found laterality is a result of the calves' preference to observe their mothers with the left eye, i.e., to analyze the information on a socially significant object in the right brain hemisphere.Data from our and previous work on cetacean laterality suggest that basic brain lateralizations are expressed in the same way in cetaceans and other vertebrates. While the information on social partners and novel objects is analyzed in the right brain hemisphere, the control of feeding behavior is performed by the left brain hemisphere. Continuous unilateral visual contacts of calves to mothers with the left eye may influence social development of the young by activation of the contralateral (right) brain hemisphere, indicating a possible mechanism on how behavioral lateralization may influence species life and welfare. This hypothesis is supported by evidence from other vertebrates

Toddling into language: Precocious language development in motorimpaired children with spinal muscular atrophy. In:

Abstract One of the most compelling topics of neurolinguistic debate is whether language has its own domain or is mediated by the same network that processes other cognitive, perceptual, and sensorimotor functions. To examine the relation between motor and language development we have collected data on motor-impaired children with Spinal Muscular Atrophy (SMA) aged 18-35 months. Analysis shows normal progress in vocabulary but marked precocity in overregularisation, a sign of early grammar development. Our finding supports the view of a separate learning system for grammar but cannot be explained by the classical account of a grammar module. It rather appears as if children with SMA explore language in place of a world they cannot reach, building grammatical knowledge while able-bodied toddlers are engaged with the physical environment. We propose that procedural learning which serves the acquisition of sensorimotor skills also has a role in language development.

Atypical maternal cradling laterality in an impoverished South African population

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