Background and Aim: Only at the onset of the second year are children able to form stable word-object associations and this point marks the beginning of a protracted period of semantic language development of which we know relatively little. The present event-related potential study aims to establish whether the language-related N400 component can be employed as an index of semantic priming in children at age 24 months. If so, the N400 component could potentially be of great value in investigations of the organization of word meaning at an early stage in language development. To address this issue an unimodal auditory semantic priming design was used.
Method: The subjects were presented for word stimuli consisting of semantically related and unrelated prime-target word pairs. In the related condition basic level words were taken from the same superordinate category (e.g. cat-horse). In the unrelated condition prime and target belonged to different superordinate categories (e.g. apple-table). The EEG was recorded with 30 silver-silverchloride electrodes attached to an elastic electrode cap. Key result: Statistical analyses revealed a significant main effect of semantic relatedness in the 600-800 ms interval after stimulus onset, where unrelated words were more negative than related words. Conclusion: The results demonstrated that in 24-month-old children target words which were preceded by a semantically unrelated word elicited a broadly distributed N400-like effect compared to target words which were primed by a semantically related word, suggesting sensitivity to semantic relatedness in this age group. The establishment of an N400-like semantic priming effect in the present experiment indicates that priming studies can be used as a functional tool in investigations of word meaning in toddlers and provides an opportunity to investigate semantic memory at a very early stage in development.