Lexical decay during online sentence processing in adults with specific language impairment

Decay of memory traces is an important component of many theories of working memory, but there is conflicting evidence on whether the rate of decay differs for individuals with specific language impairment (SLI) as compared to peers with typical language. The authors tested the hypothesis that adults with SLI have a slower decay rate.

Twenty adults with SLI, ages 18-27 years, and 23 age-matched peers identified target words in sentences. Sentences were presented at normal and slow rates. Participants separately judged whether a picture and sentence matched in meaning as a measure of sentence processing efficiency.

After controlling for sentence processing efficiency, the group with SLI was slower to detect words in sentences. Response times for the group with SLI increased less in the slow condition as compared to the group with typical language, resulting in a Group × Presentation Rate interaction.

The Group × Presentation Rate interaction is consistent with a slower lexical decay rate for adults with SLI, but differences in the ability to manage interference could not be ruled out. The findings suggest that decay rate differences may play a role in the working memory limitations found in individuals with SLI.