We investigated children's moral behaviour in situations in which a third party was harmed (the test case for possession of agent-neutral moral norms). A 3-year-old and two puppets each created a picture or clay sculpture, after which one puppet left the room. In the Harm condition, the remaining (actor) puppet then destroyed the absent (recipient) puppet's picture or sculpture. In a Control condition, the actor acted similarly but in a way that did not harm the recipient. Children protested during the actor's actions, and, upon the recipient's return, tattled on the actor and behaved prosocially towards the recipient more in the Harm than in the Control condition. This is the first study to show that children as young as 3 years of age actively intervene in third-party moral transgressions.

Reading others' emotional body expressions is an essential social skill. Adults readily recognize emotions from body movements. However, it is unclear when in development infants become sensitive to bodily expressed emotions. We examined event‐related brain potentials (ERPs) in 4‐ and 8‐month‐old infants in response to point‐light displays (PLDs) of happy and fearful body expressions presented in two orientations (upright and inverted). The ERP results revealed that 8‐month‐olds but not 4‐month‐olds respond sensitively to the orientation and the emotion of the dynamic expressions. Specifically, 8‐month‐olds showed (i) an early (200–400 ms) orientation‐sensitive positivity over frontal and central electrodes, and (ii) a late (700–1100 ms) emotion‐sensitive positivity over temporal and parietal electrodes in the right hemisphere. These findings suggest that orientation‐sensitive and emotion‐sensitive brain processes, distinct in timing and topography, develop between 4 and 8 months of age.

Responding to others’ emotional body expressions is an essential social skill in humans. Adults readily detect emotions from body postures, but it is unclear whether infants are sensitive to emotional body postures. We examined 8-month-old infants’ brain responses to emotional body postures by measuring event-related potentials (ERPs) to happy and fearful bodies. Our results revealed two emotion-sensitive ERP components: body postures evoked an early N290 at occipital electrodes and a later Nc at fronto-central electrodes that were enhanced in response to fearful (relative to happy) expressions. These findings demonstrate that: (a) 8-month-old infants discriminate between static emotional body postures; and (b) similar to infant emotional face perception, the sensitivity to emotional body postures is reflected in early perceptual (N290) and later attentional (Nc) neural processes. This provides evidence for an early developmental emergence of the neural processes involved in the discrimination of emotional body postures.

Much research has recognized the general importance of maternal behavior in the early development and programing of the mammalian offspring’s brain. Exclusive breastfeeding (EBF) duration, the amount of time in which breastfed meals are the only source of sustenance, plays a prominent role in promoting healthy brain and cognitive development in human children. However, surprisingly little is known about the influence of breastfeeding on social and emotional development in infancy. In the current study, we examined whether and how the duration of EBF impacts the neural processing of emotional signals by measuring electro-cortical responses to body expressions in 8-month-old infants. Our analyses revealed that infants with high EBF experience show a significantly greater neural sensitivity to happy body expressions than those with low EBF experience. Moreover, regression analyses revealed that the neural bias toward happiness or fearfulness differs as a function of the duration of EBF. Specifically, longer breastfeeding duration is associated with a happy bias, whereas shorter breastfeeding duration is associated with a fear bias. These findings suggest that breastfeeding experience can shape the way in which infants respond to emotional signals.

We examined the processing of facial expressions of pain and anger in 8-month-old infants and adults by measuring event-related brain potentials (ERPs) and frontal EEG alpha asymmetry. The ERP results revealed that while adults showed a late positive potential (LPP) to emotional expressions that was enhanced to pain expressions, reflecting increased evaluation and emotional arousal to pain expressions, infants showed a negative component (Nc) to emotional expressions that was enhanced to angry expressions, reflecting increased allocation of attention to angry faces. Moreover, infants and adults showed opposite patterns in their frontal asymmetry responses to pain and anger, suggesting developmental differences in the motivational processes engendered by these facial expressions. These findings are discussed in the light of associated individual differences in infant temperament and adult dispositional empathy.