The interpretation of ambiguous words in psychosis

Abstract

Semantically ambiguous words are ubiquitous in daily communication. Neurotypical individuals are able to resolve ambiguity with ease and efficiency, whereas individuals with schizophrenia tend to exhibit ambiguity-processing deficits. The exact nature of these deficits is unclear. For the disambiguation of homonyms (words with more than one meaning), impairment in schizophrenia may arise from abnormalities in the use of context – informational cues that support a particular interpretation over others – and meaning dominance – the relative frequency of meaning alternatives. The present investigation had two main parts. In one part, clinical participants (those with schizophrenia or a related disorder, i.e. schizoaffective disorder, a mood disorder with psychotic features) and control participants were asked to provide definitions for homonyms presented in sentential context, requiring them to select a single meaning. Contextual information (which always supported the less frequent, subordinate meaning of the homonym) was heard either before (PRE) or after (POST) the homonym. This manipulation of context position was expected to reflect working-memory abilities since longer on-line maintenance of the homonym and its possible interpretations would be more challenging for POST sentences. In fact working memory was found to correlate with both sentence conditions. As well, clinical participants had comparable success to control participants. In the second part, participants heard a sentence containing a homonym (PRE and POST sentences), and 20 minutes later, were asked to provide a word associate for that homonym. Participants were more likely to select the primed (subordinate) meaning of the homonym when they had heard the homonym in context 20 minutes earlier. Significantly more clinical participants than control participants did not show an effect of priming, suggesting a difficulty for these individuals to use relatively recent experience to facilitate comprehension. This ability to benefit from recent exposure would be expected to improve real-world speech comprehension wherein the correct interpretation of a homonym is not likely to change over a short period of time. Therefore, despite intact comprehension of ambiguous words in context, a majority of clinical participants could not shift their interpretation of homonyms to fit with recent exposure, a potential cause for real-world comprehension deficits.