Vespignani, F. 1 & Cacciari, C. 2
1 University of Trento
2 University of Modena Reggio Emilia
Recent neurocognitive models of language comprehension attribute a crucial role to predictive and anticipatory processing based on long term memory information. Several sources of evidence in fact show that the distributional properties of language make words rather predictable within a sentence or a text: at a processing level an appropriate context can facilitate word identification, storage, syntactic and semantic integration. The N400 component is known to be sensitive to word frequency (out of context or at sentence beginning), to semantic associations with previously processed words or pictures, and to predictability. A number of experiments showed that some of these N400 modulations, classically attributed to bottom-up integrative processes, reflect message level predictive anticipatory processing.
However a specific word can be predicted based on different sources of information. From the one side, the fact that predictions based on semantic association and world knowledge trigger similar N400 effects and the generality of the inverse relation between cloze-probability level of a constituent and N400 amplitude, suggest the existence a common neural mechanism dealing with expectations and verifications during language processing. From the other side recent ERP evidence on multiword units as idioms (e.g., "cry over spilt milk") or collocational complex prepositions (e.g., "with respect to") shows a more articulated picture with patterns other than the classic N400 effects: an interplay between P3 and N400, dissociations between lexical processing negativity and N400-700. These signatures of are discussed as evidence in favor of the existence of different cognitive mechanisms involved in the processing of unexpected constituents in specific situations. This multiplicity of psychophysiological indexes questions the idea that a unique cognitive process is responsible for processing expected constituents simply by estimating the probability of co-occurrence of words.