Memory

Most people recognize that their memories are changing as they grow older. They have a harder time coming up with names; they have a harder time finding things they need; they have to rely more on external memory cues such as notes or calendars. In fact, research results support these perceptions. The bad news from this research is that memory declines are experienced throughout the adult life span and not just in the older ages. Forty-year-olds as a group are worse than twenty-year-olds, and fifty-year-olds are worse than thirty-year-olds. The good news is that research shows that, unlike the serious and ubiquitous memory declines associated with Alzheimer's disease and other dementias, memory changes associated with healthy aging are selective (e.g., Zack et al.). Some memory tasks show large and reliable adult age differences (e.g., working memory, episodic memory), while other memory tasks show little or no effects of age (e.g., semantic memory, implicit memory).

Figure 1 shows the results from study of 345 adults ranging in age from the twenties to the eighties (Park, Lautenschlager, et al.). Different types of memory were tested, including working memory (computation span), episodic memory (free recall of a word list), and semantic memory (defining words in a vocabulary test). The results were plotted in deviation units from the mean for all the participants on any test (z scores). As can be seen in the graph, the memory changes occur across the entire adult life span and are not limited to old age. Second, the graph shows that age has selective effects on memory. Working memory and episodic memory decline significantly across the life span, while semantic memory increases significantly.

Other theories suggest that age differences in memory depend on the extent of deliberate cognitive processing or cognitive resources required to perform the task (e.g., Park). According to this view, the size of age differences in different memory tasks is determined by the amount of cognitive resources needed to adequately remember in those tasks. Other theories suggest that age effects are limited to specific memory structures or types (e.g., Craik). Clearly, the explanation for the differential effects of age with different memory tasks depends on how one conceptualizes memory.