The effect of healthy aging and mild cognitive impairment on semantic ambiguity detection

Individuals with Mild Cognitive Impairment (MCI) display cognitive deficits that distinguish them from healthy elders, but are not yet severe enough for a diagnosis of dementia. Some researchers report subtle language impairments in individuals with MCI when the required tasks rely on executive function. The present study used an on-line decision task to examine how semantic processing is affected by MCI. Thirty healthy young adults, 20 healthy older adults, and 11 individuals with MCI were administered an ambiguity decision task. Participants saw words and decided if each word had one meaning or more than one meaning. The words ranged in number of meanings (NOM: Few Meanings or Many Meanings) and intra-word meaning relatedness (Low Related or High Related). Correct response times and accuracy were measured. Overall, the MCI group responded slower than the other two groups. There was a significant NOM × Group interaction reflecting a stronger NOM effect for the MCI group than for the other two groups. A post-hoc discriminant analysis correctly classified 77.4% of the participants and was statistically significant. In making ambiguity decisions, individuals with MCI seem to experience additional semantic interference likely due to mild executive dysfunction. The observation of intra-word relatedness effects in the MCI group suggests that the semantic representations in these individuals are relatively intact and it is executive driven access to these representations that is impaired.