Age differences in text processing: the role of working memory, inhibition, and processing speed.

OBJECTIVES: Age-related changes in the efficiency of various general cognitive mechanisms have been evoked to account for age-related differences between young and older adults in text comprehension performance. Using structural equation modeling, we investigate the relationship between age, working memory (WM), inhibition-related mechanisms, processing speed, and text comprehension, focusing on surface and text-based levels of processing. METHODS: Eighty-nine younger (M = 23.11 years) and 102 older (M = 70.50 years) adults were presented text comprehension, WM, inhibition, and processing speed tasks. In the text comprehension task, the demand on the memory system was manipulated, by allowing (text present) or not (text absent) viewing the text during the answering phase. RESULTS: As expected, age differences were larger when the text was absent. The best fitting model showed that WM mediated the influence of age on both text processing conditions, whereas age-related variance in WM was, in turn, accounted for by processing speed and inhibition. DISCUSSION: These findings confirm the hypothesis that WM capacity explains age differences in text processing, while it is itself accounted for by the efficiency of inhibiting irrelevant information and by speed of processing.