The role of ambiguity in idiom comprehension: the case of a patient with a reversed concreteness effect.

The semantic structure of many idioms is constituted by concrete (literal) actions that convey abstract (figurative) mental states and events. We investigated the comprehension of idioms in an Italian patient (MC) with selective atrophy of the left temporal pole, inferior and middle temporal gyri who showed a reversed concreteness effect on nouns (Papagno et al., 2009). Since idioms convey abstract figurative meanings, we assessed whether idiom comprehension was preserved. We tested the extent to which the number of meanings associated with a linguistic unit affected her ability to provide a meaning definition for ambiguous and unambiguous idioms, and for polysemous and non-polysemous words. Only the comprehension of unambiguous idioms was impaired despite the fact that both types of idiom convey abstract mental states. Polysemous word meanings were preserved. Our results suggest that: (1) the integrity of the left temporal lobe is required to process unambiguous idioms; (2) a relatively undamaged right temporal lobe allows the comprehension of ambiguous linguistic units.