Idioms in the Aging Brain

With the world’s population getting older and older, gaining more insight into the cognitive consequences of aging is an urgent matter. Many studies have investigated the effects of aging on general cognitive abilities, such as memory. However, much less is known about the effects of aging on language abilities. This thesis investigates how cognitive aging affects healthy elderly adults’ processing of Dutch expressions that can have multiple interpretations, such as the idiom tegen de lamp lopen (literally: ‘to walk against the lamp’, figuratively: ‘to get caught’). Studying idioms is interesting, as idiom knowledge has been shown to keep increasing until old age. Idiom processing, in contrast, partly depends on cognitive functions that become increasingly vulnerable with age. Comparing young and elderly adults, we found that both use contextual information to facilitate the processing of idioms and that this ability remains stable over several years. However, older adults, but not younger adults, need additional contextual information to process sentences word by word. Also, we found that the suppression of an idiom’s literal meaning, which is necessary to select its figurative meaning, slows down from the age of 40. Additionally, elderly adults were found to be slower than young adults to activate an idiom’s figurative meaning. Taken together, we have demonstrated that linguistic processing changes slowly across the lifespan, but stays remarkably efficient until old age. These findings on language abilities in healthy elderly adults form an important baseline for research on cognitive decline due to neurodegenerative diseases such as dementia.