Department of Psychology University of Toronto
/imagine I was invited to discuss the papers because of my very early contribution to this area, which consisted of a single paragraph describing a real-life experiment on memory and aging (Moscovitch, 1982). In that study, Nina Minde21 found that older adults were as good or better than younger adults at keeping phone appointments. This age advantage on naturalistic tasks as compared to an age deficiency on laboratory-based tasks is now known as the age prospective memory paradox and has been studied extensively since then (see Phillips, Henry, & Martin, chap. 8, this volume). I return to it at the end of this commentary. I also noted that some people have incorporated some ideas from my neuropsycho-logically based, component process model (Moscovitch, 1992, 1994; Moscovitch & Winocur, 1992) into their theories of prospective memory (see especially the work of McDaniel & Einstein summarized in this). Although I have a nodding familiarity with some of the current literature on the topic, my comments are not those of an expert, but of an interested observer. From that point of view, I found the following chapters in this book by Kliegel, Jäger, Altgassen, and Shum (chap. 13, this volume), West (chap. 12, this volume), and Burgess et al. (chap. 11, this volume) to be not only enjoyable, but enlightening.
Three major themes are apparent in reading the chapters. The first, which the authors perhaps take for granted and so do not state explicitly, is that research on prospective memory is about the only major enterprise in memory research in which the problem is not memory itself, but the uses to which memory is put. This is an extremely neglected area of research, with the vast majority of papers on memory dealing only with memory itself, as if memory evolved for its own sake rather than for the service of action or goal-directed behavior. This tendency to separate cognition from action is not peculiar to research on memory but can be found in other domains, such as perception, even though there is much evidence to indicate that doing so provides an incomplete, and probably erroneous, view of how cognition works (Goodale &Wolf, 2006). The essays on prospective memory do not go so far as to speculate how, or if, our views of retrospective memory would be altered by thinking of the uses to which it is put, although such considerations have contributed to evolving views of perception (Goodale & Milner, 1992; Goodale & Milner, 2004). Nonetheless, research on prospective memory moves things in the right direction (see especially Zimmer et al., 2006).
The second major theme is front and center in all the chapters: What are the components of prospective memory? Each of the chapters addresses this issue in a number of ways. What they all acknowledge is that prospective memory is a com-plexfunction, to use Burgess et al.'s nomenclature, that requires the identification of various constructs that contribute to the execution of that function. As I understand it, Burgess et al.'s use of the term construct, insofar as it applies to things such as memory, refers to what I call components. I hope Burgess et al. will forgive me for adopting my own terminology, with which I am more comfortable. Thus, research on prospective memory requires the identification of various components that make it up. What was surprising to me, however, was how much weight the concept of prospective memory had been made to bear, and how many components are now considered part of the function or concept of prospective memory. Prospective memory not only embodies the requirement to carry out some particular task in the future, but also to keep in mind a number of such tasks and the rules for executing them, to select among the best alternatives, to devise and keep in mind an order (plan) in which to carry them out, and to monitor the outcome to see if the tasks we executed according to plan. The multiple elements tasks that began with Shallice and Burgess's (1991) attempt to capture in a "laboratory" (I put this in quotation marks because some of the tasks actually were required to be executed on the street) the difficulties that some of their patients had in leading productive lives despite adequate perception, memory, and intelligence have now been incorporated into the general framework of prospective memory by many researchers in the field (see Burgess et al., chap. 11, this volume; Kliegel et al., chap. 13, this volume; Levine et al., 1998). Although everyone acknowledges that in real life knowing how to plan one's activities requires all these components, I think it is a mistake to include them in a scientific investigation of prospective memory, if one wants to get to the bottom of what is unique to it, as compared, say, to decision making under uncertainty, or to solving open-ended problems, or to planning in general.
How prospective memory interacts with those functions and the cognitive processes that mediate them is an interesting question in its own right, but it presupposes that we first know something about prospective memory independently of these other aspects. It may even be the case that prospective memory shares components with each of these other functions, but that is something to be proven, not something to be assumed at the beginning. My reading of the chapters suggests that all the authors would agree with many of these observations, although they sometimes blur the distinctions I am making. In rereading the chapters, a good exercise would be to isolate what one believes is peculiar to prospective memory and leave aside the other aspects of the tasks to get at what is special about prospective memory.
The third major theme is linked closely to the second, namely, to identify the neural substrates or correlates that are associated with the various components of prospective memory. This enterprise needed to await the development of some good theories of prospective memory before it became worthwhile. Such theories are now available, and the cognitive neuroscience of prospective memory not only complements these theories by helping to specify the neural mechanisms that support the different components that comprise prospective memory, but also can be used to determine the cognitive components themselves or corroborate that they are crucial. In short, evidence from neuropsychology and cognitive neuroscience can inform psychological theory. Thus, for example, by first demonstrating that rostral prefrontal cortex (area 10) is implicated in prospective memory tasks, and then by showing that it also is implicated on other tasks that involve stimulus-independent cognition, Burgess and his collaborators (chap. 11, this volume) bolster their case that stimulus-independent cognition is a crucial component of prospective memory.
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