How much do working memory deficits contribute to age differences in discourse memory?

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Abstract
Younger and older adults listened to and recalled a series of expository passages that were systematically varied in terms of propositional density and prose length. The working memory processing efficiency of these subjects was also estimated using a sentence span task that estimated their ability to hold verbal items in memory during language processing, and a word span task that estimated their ability to simply hold items in working memory without a simultaneous processing load. Older adults demonstrated lower levels of recall than younger adults. Additionally, age differences in recall were slightly exaggerated by increased propositional density, but not by increased passage length. In a correlational analysis, age was found to be a strong predictor of recall performance. For simpler texts, these age effects could be accounted for in terms of individual differences in working memory storage capacity. For more difficult passages, however, age effects could not be completely explained in terms of age differences in working memory span. Thus, working memory capacity provided greater explanatory power in accounting for age differences when texts were simpler.