Neural signatures for sustaining object representations attributed to others in preverbal human infants
A major feat of social beings is to encode what their conspecifics see, know or believe. While various non-human animals show precursors of these abilities, humans perform uniquely sophisticated inferences about other people’s mental states. However, it is still unclear how these possibly human-specific capacities develop and whether preverbal infants, similarly to adults, form representations of other agents’ mental states, specifically metarepresentations.We explored the neurocognitive bases of eight-month-olds’ ability to encode the world from another person’s perspective, using gamma-band electroencephalographic activity over the temporal lobes, an established neural signature for sustained object representation after occlusion. We observed such gammaband activity when an object was occluded from the infants’ perspective, as well as when it was occluded only from the other person (study 1), and also when subsequently the object disappeared, but the person falsely believed the object to be present (study 2). These findings suggest that the cognitive systems involved in representing theworld from infants’ own perspective are also recruited for encoding others’ beliefs. Such results point to an early-developing, powerful apparatus suitable to deal with multiple concurrent representations, and suggest that infants can have a metarepresentational understanding of other minds even before the onset of language.
Electrophysiological Evidence for the Understanding of Maternal Speech by 9- Month-Old Infants
Early word learning in infants relies on statistical, prosodic, and social cues that support speech segmentation and the attachment of meaning to words. It is debated whether such early word knowledge represents mere associations between sound patterns and visual object features, or reflects referential understanding of words. By using event-related brain potentials, we demonstrate that 9-month-old infants detect the mismatch between an object appearing from behind an occluder and a preceding label with which their mother introduces it. The N400 effect has been shown to reflect semantic priming in adults, and its absence in infants has been interpreted as a sign of associative word learning. By setting up a live communicative situation for referring to objects, we demonstrate that a similar priming effect also occurs in young infants. This finding may indicate that word meaning is referential from the outset, and it drives, rather than results from, vocabulary acquisition in humans.