The dynamics of memory retrieval in older adulthood.

Abstract One of the most robust findings in cognitive aging is that of a significant decline in self-initiated recall from episodic memory. In laboratory studies this deficit can be seen in significant age differences in word-list free recall. In this article, we focus on free recall of categorized word lists where one observes "response bursting" in the form of a rapid output of within-category items with longer delays between categories. Age differences appear primarily in between-- category latencies, results that are consistent with a relative sparing of semantic memory combined with an age-deficit in episodic retrieval. When adjusted for differences in overall mnemonic ability, we demonstrate that the relationship between organization and learning remains invariant with normal aging. We argue that the locus of the age deficit in free recall lies at the level of temporal coding of items and the use of temporal associations to guide recall. One of the most common complaints among older adults is that of increasing difficulty with memory for recently experienced events, to include recently learned names, list of things to do, or narratives relating to recent activities of family and friends (Cutler & Grams, 1988; Dobbs & Rule, 1987; Gilewski & Zelinski, 1986). These difficulties are highlighted in laboratory tasks that involve explicit episodic memory. These include tests of free recall, paired-associate learning, and recognition memory (Craik & Jennings, 1992; Hartley, 1989, 1993; Moscovitch & Winocur, 1992; Light, 1991). However, not all of these are affected equally. For example, it is well known that age differences are larger in tests of free recall than for tests involving recognition or cued recall (Burke & Light, 1981; Craik, 1977; Craik & McDowd, 1987; Perry & Wingfield, 1994). These data support the general view that age-related memory changes are particularly pronounced in explicit memory (Mitchell, 1989; Schacter, Chiu, & Ochsner, 1993), and tasks that involve controlled processing (Jacoby, 1991). Unlike recognition memory and cued recall, free recall requires the individual to initiate the formation of the retrieval cues that may facilitate access to the desired information. It may be for this reason that deliberate recollection (i.e., free recall) is among the most age-sensitive of cognitive tasks (Craik & Jennings, 1992). An additional factor in self-initiated recall is that success requires the effective inhibition of related, but nontarget, memories (Hasher & Zacks, 1988; Zacks, Hasher, & Li, 2000). Indeed, failure at achieving this inhibition may result in the production of false memories (Roediger & McDermott, 1955), a problem that is exaggerated among older adults (Norman & Schacter, 1997; Tun, Wingfield, Rosen, & Blanchard, 1998). Adult Aging and Retrieval Mechanisms in Free Recall These and other findings in cognitive aging cannot be fully understood without a detailed theoretical understanding of the retrieval mechanisms in free recall in young and older adults. After some years of neglect, the general cognitive literature has shown a resurgence of interest in the retrieval dynamics of free recall from episodic memory (Howard & Kahana, 1999; Kahana, 1996; Kahana & Loftus, 1999; Rohrer, Wixted, Salmon, & Butters, 1995; Wixted & Rohrer, 1996). Although classical ideas of association and interference were largely replaced by more cognitive constructs in the 1960s and 1970s, more recent neural and computational models of memory have brought the earlier focus on simple associations to the foreground of contemporary theory. This new approach, however, has been able to overcome the limitations of classical association theory by providing much more powerful models for describing the mechanisms of associative storage and retrieval. We believe that a fruitful approach to understanding the problem of the age-related deficits in human learning and memory is to take models of normative memory function that have been successful in accounting for a wide range of data in young adults, and then determining how "lesioning" such a model would produce behaviour that is isomorphic with the known pattern of memory changes in older adulthood. …