Syntactical regularities of action sequences in the infant brain: when structure matters

Throughout life, actions and language are inherent to social interactions. A long-standing research question in cognitive neuroscience concerns the interrelation between verbal and non-verbal forms of social interactions, that is, language and action. Perceiving how actions are performed and why they are performed in a certain way is crucial for the observer to anticipate the actor's goal and to prepare an appropriate response. It is suggested that predicting upcoming events in a given action sequence can be compared to the way we process the language information flow. Goal-directed actions can be sequenced in small units, which are organized according to a hierarchical plan, resembling the hierarchical organization of language. Research on adults suggests that manipulating the action structure (i.e., action syntax) leads to analogous cortical signatures as a similar manipulation of a sentence structure (i.e., language syntax). Whereas in adults language and action knowledge are based on life-time experience, in infants both domains are still developing. The current study examined the neural processing of structural violations of observed goal-directed action sequences in infants at 6-7 months, using event-related potentials (ERPs). Results showed that a structural violation of the action sequence elicited bilateral frontal positivity effects. This suggests that infants capture structural regularities, and it adds a crucial element to the understanding of general syntactic regularities and their violation from an ontogenetic perspective.