Conventional metaphor processing in autistic adults: a semantic priming experiment

In typical development, conventional metaphors are represented as senses of polysemous expressions rather than as meanings of homonymous terms. Conventional metaphors and the literal meanings they relate to are stored in the same lexical entry, unlike the meanings of homonyms, which are stored in separate lexical entries. Understanding metaphorical relations can be challenging for autistic individuals. It is therefore possible that autistic individuals do not perceive the relation between conventional metaphors and the corresponding literal meanings, so that they end up representing conventional metaphors in separate lexical entries. In this paper we put this idea to test. We compared the performance of a group of autistic adults and a group of non-autistic adults on a lexical decision task involving homonyms and conventional metaphors. We hypothesized that, in the autistic group, we would observe inhibition effects for subordinate meanings of homonyms as well as for conventional metaphors. In the non-autistic group, in line with several previous investigations, we expected to observe inhibition effects only in the case of subordinate meanings of homonyms. Our results for the non-autistic group show that senses corresponding to conventional metaphors are as difficult to access as subordinate meanings of homonyms. In the case of the autistic participants, we found a different pattern: senses corresponding to conventional metaphors were more difficult to access than subordinate meanings of homonyms. Conventional metaphorical senses were also more difficult to access in the case of autistic participants than in the case of non-autistic participants. Such results show that accessing the meaning of a conventional metaphor is particularly challenging for autistic individuals, suggesting strong inhibition effects by the literal competitor.