Individual word activation and word frequency effects during the processing of opaque idiomatic expressions.

Idiom processing studies have paid considerable attention to the relationship between idiomatic expressions as a whole and their constituent words. Although most research focused on the semantic properties of the constituent words, their orthographic form could also play a role in processing. To test this, we assessed both form and meaning activation of individual words during the processing of opaque idioms. In two primed word naming experiments, Dutch native speakers silently read sentences word by word and then named the last word of the sentence. This target word was embedded in either an idiomatic or a literal context and was expected and correct in this context (COR), semantically related (REL) to the expected word, or unrelated (UNREL) to the expected word. The correct target word in the idiomatic context was always part of an opaque idiom. Faster naming latencies for the idiom-final noun than for the unrelated target in the idiomatic context indicated that the idiom was activated as a whole during processing. In addition, semantic facilitation was observed in the literal context (COR < REL < UNREL), but not in the idiomatic context (COR < REL = UNREL). This is evidence that the idiom-final noun was not activated at the meaning level of representation. However, an inhibitory effect of orthographic word frequency of the idiom-final noun indicated that the idiom-final noun was activated at the form level. These results provide evidence in favour of a hybrid model of idiom processing in which the individual words and the idiom as a whole interact on form and meaning levels of representation.