Flexible composition: MEG evidence for the deployment of basic combinatorial linguistic mechanisms in response to task demands.

Abstract

The present study investigates whether a minimal manipulation in task demands can induce core linguistic combinatorial mechanisms to extend beyond the bounds of normal grammatical phrases. Using magnetoencephalography, we measured neural activity evoked by the processing of adjective-noun phrases in canonical (red cup) and reversed order (cup red). During a task not requiring composition (verification against a color blob and shape outline), we observed significant combinatorial activity during canonical phrases only - as indexed by minimum norm source activity localized to the left anterior temporal lobe at 200-250 ms(cf. [1], [2]). When combinatorial task demands were introduced (by simply combining the blob and outline into a single colored shape) we observed significant combinatorial activity during reversed sequences as well. These results demonstrate the first direct evidence that basic linguistic combinatorial mechanisms can be deployed outside of normal grammatical expressions in response to task demands, independent of changes in lexical or attentional factors.