Individual differences in infants' neural responses to their peers' cry and laughter

Infants' ability to process others' emotional expressions is fundamental for their social development. While infants' processing of emotions expressed by faces and speech has been more extensively investigated, less is known about how infants process non-verbal vocalizations of emotions. Here, we recorded frontal N100, P200, and LPC event-related potentials (ERPs) from 8-month-old infants listening to sounds of other infants crying, laughing, and coughing. Infants' temperament was measured via parental report. Results showed that processing of emotional information from non-verbal vocalizations was associated with more negative N100 and greater LPC amplitudes for peer's crying sounds relative to positive and neutral sounds. Temperament was further related to the N100, P200, and LPC difference scores between conditions. One important finding was that infants with improved ability to regulate arousal exhibited increased sustained processing of peers' cry sounds compared to both laughter and cough sounds. These results emphasize the relevance of considering the temperamental characteristics in understanding the development of infant emotion information processing, as well as for formulating comprehensive theoretical models of typical and atypical social development.