Understanding the Relations among Episodic Memory, Associative Learning, and Fluid Intelligence in Younger and Older Adults

Age-related changes in episodic memory are hallmarks of aging (Balota, Dolan, & Ducheck, 2000). However, there is still debate as to what underlies episodic memory declines. Two hypotheses, the associative deficit hypothesis (Naveh-Benjamin, 2000) and the environmental support hypothesis (Craik, 1983), were evaluated as possible explanations. The associative deficit hypothesis predicts that age-related differences are greater in tasks that require binding of memory items or features of an item, whereas the environmental support hypothesis argues that age-related differences are greater in tasks that do not provide participants with retrieval cues at the time of test. Under certain circumstances, like those studied here, these hypotheses make different predictions for age-related differences in episodic memory. In order to test these hypotheses, participants completed verbal and spatial versions of three different learning tasks: list recall, paired-associate, and complex association learning. The tasks differed both in the amount of binding required and in the amount of retrieval cues provided at test. The associative deficit hypothesis predicts that age-related differences will be greater on paired-associate and complex association learning tasks relative to performance on list learning tasks. In contrast, the environmental support hypothesis predicts that age-related differences will be greater on list learning tasks relative to performance on paired-associate and complex association learning tasks, both of which provide retrieval cues for support at recall. These three learning tasks not only allowed for the examination of age-related differences in episodic memory, but performance on these learning tasks along with performance on fluid intelligence tasks also allowed for the examination of the predictive utility of learning for individual and age-related differences in fluid intelligence. With respect to this second issue, two separate questions were addressed: First, is complex association learning or general learning ability the better predictor of fluid intelligence, and second, does learning account for unique variance in fluid intelligence after controlling for other cognitive abilities? The second question was addressed in the context of a cognitive cascade model in which the relations among several cognitive variables (i.e., processing speed, working memory, and secondary memory) were examined with learning as a potential mediator of age-related differences in fluid intelligence. In regard to age-related differences in episodic memory, the results of the current study were consistent with the associative deficit hypothesis and provide evidence against the environmental support hypothesis. Age differences were found to be greater on the paired-associate learning task and the complex association learning task relative to the list learning task, consistent with the associative deficit hypothesis but the exact opposite of what is predicted by the environmental support hypothesis. This associative deficit was observed in both initial learning and final learning memory performance, and in both the verbal and spatial domains. Thus, as suggested by Naveh-Benjamin (2000), older adults are more impaired in the ability to encode or retrieve associations as opposed to individual items. Further, associative learning among older adults was an important predictor of fluid intelligence. However, among younger adults, individual differences in learning in general, and not just associative learning, were predictive of fluid intelligence. The present findings demonstrate that learning is an important predictor of fluid intelligence in both young and older adults