Heating up or cooling up the brain? MEG evidence that phrasal verbs are lexical units.

There is a considerable linguistic debate on whether phrasal verbs (e.g., turn up, break down) are processed as two separate words connected by a syntactic rule or whether they form a single lexical unit. Moreover, views differ on whether meaning (transparency vs. opacity) plays a role in determining their syntactically-connected or lexical status. As linguistic arguments could not settle these issues, we used neurophysiological brain imaging to address them. Applying a multi-feature Mismatch Negativity (MMN) design with subjects instructed to ignore speech stimuli, we recorded magnetic brain responses to particles (up, down) auditorily presented as infrequent "deviant" stimuli in the context of frequently occurring verb "standard" stimuli. Already at latencies below 200ms, magnetic brain responses were larger to particles appearing in existing phrasal verbs (e.g. rise up) than to particles appearing in non-existing combinations (e.g. ∗fall up), regardless of whether particles carried a literal or metaphorical sense (e.g. rise up, heat up). Previous research found an enhanced MMN response to morphemes in existing (as opposed to non-existing) words but a reduced MMN to words in grammatically acceptable (as opposed to unacceptable) combinations. The increased brain activation to particles in real phrasal verbs reported here is consistent with the lexical enhancement but inconsistent with the syntactic reduction of the MMN, thus providing neurophysiological support that a congruent verb-particle sequence is not assembled syntactically but rather accessed as a single lexical chunk.