No evidence for rational adaptation during verb-argument processing in aphasia

Rational adaptation (RA) theories argue that people differ in how heavily they rely on knowledge about language versus event likelihood when they understand sentences depending on which type of knowledge is more reliable for them. Findings from multiple paradigms hint that, in language tasks, people with aphasia (PWA) rely more on world knowledge than neurologically healthy controls do. We tested rational adaptation theories in PWA using a visual world eye-tracking study of sentence comprehension. Both PWA and healthy controls showed similarly strong influences of world knowledge and verb constraints, with a slight delay in PWA, contrary to predictions of RA theories. Additionally, PWA showed more interference from a semantically-related distractor. These findings together do not provide clear evidence in favour of RA theories' predictions, but are consistent with models suggesting that impaired control mechanisms may play a role in language processing deficits in aphasia.