Cerebral asymmetry of emotion and its relationship to olfaction in infancy

Abstract

To examine the relationship between emotional development and laterality, smells differing in affective valence (predetermined by adults) were presented to 10 neonates. Each infant was presented with two positive and two negative foodrelated odorants, each paired with a neutral stimulus. Each pair was presented twice, once with the odorant to the right nostril and once to the left nostril. These eight trials were repeated in two blocks. In addition, control trials, where a puff of air was administered to both nostrils, were included. Head turning from midline position to presentation of the odorants as videotaped while the infant slept. Direction of initial head turn served as the dependent measure. A significant interaction with Smell 2 Nostril 2 Direction was found. Post hoc analyses revealed that significant effects occurred only for the positive smells. When the positive smells were presented to the left hemisphere, neonates made significantly more head turns towards the smell. This raises the possibility that approach behaviours may develop earlier than withdrawal behaviours.