Neuropsychological and neuropsychiatric perspectives on maternal cradling preferences.

Abstract

To assess competing explanations for the universal preference of mothers to cradle infants on their left side and to propose a relation to hemispheric asymmetry for social attachment and communication behaviour. A review of observational, experimental, physiological, psychological, neuro-physiological, and neuro-psychological studies, including new findings on the cradling behaviour of mothers with auditory or visual impairments. A significant left-cradling bias is observed in both right- and left-handed mothers which cannot adequately be explained by arguments based on handedness or closer contact to the soothing sound of the maternal heartbeat. Observations of primate behaviour have led to the suggestion that the left-cradling bias may be related to a left visual field (right hemisphere) advantage for monitoring an infant's facial expressions of distress. However, more than just monitoring, cradling subserves the mother's connection with the infant. For that reason, we have suggested that left cradling might be related to a right hemisphere specialisation for emotional communication, i.e. the speech melody, smiles, signals, and stroking which mothers use to interact with their infants. Studies of mother-infant interaction show that the sound of the mother's voice is more soothing when cradling on the left, more stimulating when cradling on the right. Cradling laterality may thus be related to emotional state and behavioural intent. There is also evidence to suggest that left cradling is linked to a special role of the right hemisphere in social attachment behaviour. This function may be disturbed in mothers with post-natal depression who show abnormal right hemisphere activity. Cradling embodies the symbiotic relationship between mother and infant; various lines of evidence support the suggestion that the universal preference of mothers to cradle infants on their left side is related to a right hemisphere dominance for social attachment and communication behaviour.