Level of processing and reaction time in young and middle-aged adults and the effect of education

The first aim was to examine whether differences in reaction time (RT) between younger (25-35 years) and middle-aged (50-60 years) individuals increase with depth of processing. The second aim was to examine whether this increase is less pronounced in higher educated individuals. Processing of words at the perceptual, phonological, and semantic level was induced by a case decision, an e detection, and a living/nonliving discrimination task, respectively. RTs increased with age and level of processing. However, there were no interactions between age, task, and education, suggesting that different processing levels are equally sensitive to slowing in midlife and that education was not a moderating factor. Although no overall age by level of processing interaction was found, there were age by stimulus type interactions in the deeper processing tasks. First, age-related differences in RT for words containing the letter e were smaller than for words without the letter e, suggesting that middle-aged adults were slower than younger adults in performing a terminating search strategy. Second, age-related differences in RT for words referring to living items were smaller than for words referring to nonliving items. This suggests that middle-aged adults compared to younger adults have reduced access to specific semantic categories. Taken together, the results show that vulnerability to age-related cognitive decline already exists in middle age.