Decades of research have demonstrated that normal aging accompanies cognitive change. Much of this change has been conceptualized as a decline in function. However, age-related changes are not universal. Oft-found decrements in older adult performance may be moderated by experience, genetics, and environmental factors. To date, cognitive aging has largely emphasized biological changes in the brain, with less evaluation of the range of external contributors to behavioral manifestations of age-related decrements in performance. The goal of this book is to examine cognitive aging through the lens of a life course perspective. Understanding cognition within the context of both the life span (aging) and the life course (experience) is a relatively new approach to the field of cognitive aging. However, the approach has already pushed the field forward in theoretically and practically important ways.

This chapter reviews major theories of cognitive aging. Theories such as the sensory deficit hypothesis, speed of processing, and inhibitory deficit hypothesis are based largely on behavioral findings and focus on a single process that is purported to account for a number of cognitive changes with age. Specific to memory, theories focus on age deficits in recollection and binding. Over the past twenty-five years, brain-based models have begun to pervade the literature. These have focused on concepts such as compensation, dedifferentiation, and suppression of the default mode network. The scaffolding theory of aging and cognition integrates many of these concepts into a single comprehensive model, including consideration of enrichment and depletion factors that operate over the life span. We conclude the chapter with some debates, critiques, and consideration of future directions, particularly considering the contributions of cognitive neuroscience methods.

A great deal of research has attempted to clarify the nature and mechanisms underlying memory in individuals, and there is an increasing amount of work concerning collective remembering by societies and cultures. However, there have been few attempts to bridge the gap between these two levels of analysis, and the present volume represents a welcome step in that direction. There are, of course, many possible ways to try to bridge the divide between individual and collective memory. In the present chapter, we adopt an approach that reflects our backgrounds as researchers in the area of individual memory: we focus on a broad concept that has important implications for how we think about individual memory and that, we suggest, might also be relevant to the understanding of collective memory.

We refer to this concept as the specificity of memory: the extent to which, and sense in which, an individual's memory is based on retention of specific features of a past experience, or reflects the operation of specialized, highly specific memory processes. In some situations, memory is highly specific, and may include the precise details of a previous experience; in other situations, memory may be much more generic, including retention of only the general sense or gist of what happened. For example, when asked about last year's summer vacation, we may be able to recall in detail the exact meal we ate at a favorite restaurant, where we sat, who else was present, what the room looked like, and how we felt about the food we ate.