The N300 ERP component reveals developmental changes in object and action identification.

Semantic mastery includes quickly identifying object and action referents in the environment. Given the relational nature of action verbs compared to object nouns, how do these processes differ in children and adults? To address this question the Event Related Potentials (EPRs) of 8-9 year olds and adults were recorded as they performed a picture-matching task in which a noun (chair) or verb (sit) was followed by a picture of an object and action (a man sitting in a chair). Adults and children displayed similar central N400 congruency effects in response to objects and actions. Developmental differences were revealed in the N300. Adults displayed N300 differences between congruent and incongruent items for both objects and actions. Children, however, exhibited an N300 congruency effect only for objects, indicating that although object noun representations may be adult-like, action verb representations continue to solidify through middle childhood. Surprisingly, adults also exhibited a posterior congruency effect that was not found in children. This is similar to the late positive component (LPC) reported by other studies of semantic picture processing, but the lack of such a response in children raises important questions about the development of semantic integration.