P1: JPL 0521826322c03.3.xml CU2059B-Johnson July 5, 2005 5:35 CHAPTER 3.3 Age-Related Changes in Memory ELIZABETH A . MAYLOR It is commonly believed that memory declines in old age. This chapter examines evidence from laboratory-controlled studies of ageing memory and asks whether changes are universal (i.e., associated with all types of memory) or whether certain types are more affected than others. Before describing the data, it is useful to begin with a brief outline of some recent theoretical approaches to ageing memory, fol- lowed by a summary of the ways in which memory has been subdivided in the literature. THEORETICAL OVERVIEW Effects of old age on memory have been interpreted in terms of three main theoretical frameworks, namely, limited processing resources, reduced pro- cessing speed and impaired inhibitory function- ing. The limited processing resources approach (e.g. Craik, 1986) supposes that older people are limited in the resources they have available for encoding information into memory and then for retrieving information from memory. Thus they are less able to carry out resource-demanding operations such as linking items together on a list or organizing retrieval in a systematic way. This self-initiated pro- cessing is particularly required when the environ- ment itself does not provide many cues at either encoding or retrieval. Evidence consistent with this general view comes, for example, from the finding that age deficits are greater in memory tasks that are more demanding of processing resources, such as recalling an item rather than simply recogniz- ing it as having been encountered earlier (Craik and McDowd, 1987). The reduced processing speed hypothesis stems from the ubiquitous observation of mental slow- ing in old age. Salthouse (1996: 403) proposed two mechanisms that underlie the relationship between processing speed and age differences in cognition. The limited time mechanism suggests that ‘cognitive performance is degraded when processing is slow because relevant operations cannot be successfully executed’; the simultaneity mechanism proposes that ‘products of early processing may no longer be avail- able when later processing is complete’. Thus, even when allowed unlimited time, older adults’ perfor- mance in a memory task may not match that of young adults. Support for the processing speed the- ory comes, in part, from studies in which the age- related deficit in memory is greatly attenuated when a simple measure of perceptual motor speed is sta- tistically taken into account (see Salthouse, 1996). On the impaired inhibitory functioning view (Hasher and Zacks, 1988), the claim is that older adults have less inhibitory control over the con- tents of their memory than do young adults. Inhibi- tion is required both to prevent distracting or goal- irrelevant information from entering memory, and to prevent information remaining in memory when no longer relevant. With impaired inhibitory func- tioning in old age, memory is assumed to be clut- tered up with distracting information during both encoding and retrieval of goal-relevant information. The inhibition deficit hypothesis has created much debate (see discussion papers in the Journal of Geron- tology: Psychological Sciences, 1997, 52B: P253–83) but also supportive evidence from a variety of paradigms as summarized by Hasher et al. (1999). 200