We’re all familiar with the following scenario: You use the last pat of butter at breakfast and make a mental note to go to the store after work. Next morning, you realize your best intentions weren’t enough to put butter on the table.
When was the last time you forgot something? Posing the question makes it clear our memory often leaves us in the lurch. We forgot to buy something, call someone, take a medication, send a letter or attach a file to an e-mail. What do all these situations have in common? In each case, it is something we decided to do seconds, minutes, hours or even days ago. Although this form of memory often presents problems in daily life, neuroscientists and psychologists have only been researching this phenomenon as an independent area of memory for about 40 years.
We need this “prospective” memory (also called memory for intentions) so we can remember to do things in the future in a timely manner. In this sense it differs from other phenomena that have been the subject of classical memory research for decades, which may be characterized as “retrospective” memory. The latter makes it possible for us to recall knowledge or earlier experiences; prospective memory, on the other hand, enables us to bring to mind future intentions. Retrospective memory is useful in recalling previously stored information as required—for example, when being asked to so on a memory test. In prospective memory that aspect of explicitly prompting memory retrieval is missing, because in everyday life no one else is usually there in real time to remind us to retrieve our intentions. What makes this type of memory so tricky is that we have to remember that the market we pass on the way home is supposed to remind us of what we need to get in the first place.
Prospective memory is crucial for two reasons: First, it is the type of memory that poses the most problems for us in everyday life. Studies have shown that as many as two thirds of memory glitches may be attributed to failures of prospective memory. At the same time, we need it to come to terms with our everyday circumstances. It is important to remember to take a medication, congratulate a friend on her birthday or get to a business meeting on time. That is what prospective memory enables us to do. If we could not recall such future intentions, we could not live autonomous and independent lives. To the extent that we are unable to remember prospectively, we will need help because such memory lapses are dangerous, for example, when we forget food cooking on the stove. Problems of this sort are one of the reasons why senior citizens or persons with a brain disorder may need a caregiver or institutionalization.
If prospective memory is so important, why has it taken so long for researchers to focus on it? The reason is that they considered situations in which prospective memory comes into play merely as everyday examples of other areas of memory. Among other things, they thought remembering items to be done, such as shopping, consisted merely of “saving” and then later recalling such items, as is the case with other short-term or long-term memory tasks. Simply knowing the items on a to-do list is not sufficient, however. One also has to remember one has to go to the store.
Many Possible Sources of Error
Researchers now distinguish between two components of prospective memory: a retrospective component that is very similar to traditional memory and relates to the content of an intention (remembering what one needs to do), and a prospective component (recalling in a timely manner that one needs to do something). Problems may occur with both components. For example, we may forget to act on an intention at the right moment if we are preoccupied with something else, for instance. This is an example of a lapse in the prospective component. Or we may become aware at a meeting that we can no longer recall all of the points we wanted to bring up, a failure of the retrospective component (see “The four steps from intention to implementation”). Interestingly, adults are relatively good at remembering what they want to do but may have problems actually doing it at the right time. In other words, the prospective dimension seems to pose problems for which few remedies have yet been found. What good is a shopping list if we find it unused in our pants pocket after we get home?
Psychologists Mark McDaniel of Washington University in Saint Louis and Gilles Einstein of Furman University in South Carolina have suggested two potential mechanisms by which people carry out their intentions: First, we may actively try to remember something at the right time. We will do everything we can not to forget the critical moment, especially if something personally important is at stake. We look at our watch regularly so the cake doesn’t burn in the oven or we don’t miss an important meeting. But it can also happen that an intention suddenly springs to mind, although we hadn’t really thought about it much before.
We do not know exactly how this second mechanism works. It may be that something in our surroundings suddenly reminds us of our plan via association, such as recalling buying cupcakes when passing a coffee shop ad down the street. Although this passive mechanism functions relatively effortlessly, the more active version requires attention that must be withdrawn from other tasks, some of which may also be important. As we would expect, it is therefore more difficult and more prone to failure than the passive mechanism. Because many of the tasks we need to do are so important, we must rely on the active mechanism. This is one of the reasons why people working in situations that are heavily dependent on prospective memory, such as air traffic controllers, work short shifts and take lots of breaks.
Neuroscientists have now shown where in the brain these two pathways for implementing intentions are located. When the active mechanism is in play, networks in the anterior prefrontal cortex are activated. This area is involved especially when our attention is directed to something new. The other pathway makes use of networks located in the parietal and ventral regions that, among other things, are involved in autobiographical memory and the discovery of relevant visual stimuli.
Prospective memory is so important to navigating daily life that it is important to understand whether it decays with age—and if so, how. We are attempting to do just that in our laboratory in Geneva, Switzerland, at the Center for the Interdisciplinary Study of Gerontology and Vulnerability (CIGEV). Fergus Craik, a pioneer in cognitive memory psychology at the Rotman Research Institute in Toronto provided the impetus for this research. As early as the mid 1980s he made the assumption prospective memory in particular becomes more unreliable in older persons, because it requires a great deal of attention. This assumption was later confirmed in many experiments in which the test subjects were asked to recall previously agreed-to tasks (for example, to press a button as soon as a certain word was said). Yet, in some studies, younger and older persons performed about the same—there were even a few where older subjects did better. More and more researchers began to get involved in the study of prospective memory to resolve this contradiction. And they brought an unusual phenomenon to light: the age-prospective-memory paradox.
When Elders Do Better
If we test subjects at home with everyday tasks (for example, remembering to call someone twice a day), older people do better than younger ones—although the effect is precisely the opposite in the laboratory. This finding raises two important questions, which our team and colleagues throughout the world are examining: How is the odd discrepancy between laboratory and everyday life to be explained? And does prospective memory become less reliable with age or does it not?
Tasks performed under laboratory conditions and those performed in daily life differ in various ways. In the laboratory memory is usually tested using standardized tasks that require multitasking. Under these conditions test subjects are generally unable to come up with mnemonic devices or use such memory aids as kitchen timers or to-do lists. For example, participants may be asked to look at a video and press a button every five minutes, tasks thatch have no intrinsic meaning to them. This may well be why they perform less well in the laboratory than out in the world, where priorities must be established and forgetting can have real consequences. In addition, the time span over which test subjects must retain something in memory is considerably shorter than it is in everyday life.
At the same time, the lives of younger and older people are not really comparable. The former are often engaged in study, must manage a variety of tasks and navigate unexpected situations; the lives of the latter are usually more predictable and follow a less chaotic rhythm. This circumstance makes it easier to remember. In addition, younger people may be more used to laboratory tests or feel less stressed in this setting. In addition, we cannot rule out that an exaggerated self-image may play a role in the age paradox. Although both age groups underestimate their prospective abilities in the lab, only the younger participants tended to overestimate their performance in their usual, familiar environment. This may lead to their being less well prepared for a task.
Does prospective memory decrease as we age? If we focus only on laboratory experiments the situation is clear: This area of memory, too, becomes less reliable with age. Studies done in people’s own environments, however, have shown the capacity we need to maintain our daily lives remains intact for quite a long time, as long as we stay healthy. We are not yet able to answer the question conclusively, because too few studies have been conducted on the performance of different age groups in everyday life.
Future research must examine at least three dimensions of prospective memory: First, more experiments are needed on everyday life. Only sophisticated methods that do not interfere with the daily lives of test subjects will enable us to measure their prospective memory in a natural setting. Second, we must closely examine noncognitive factors such as motivations, emotions and stresses in order to understand this memory system. Finally, understanding the age-prospective-memory paradox may provide an opening for research aimed at maintaining certain cognitive processes and even improving them over the life span. There is some reason to hope a change in perspective from the deficits experienced by older people to the capacities that remain intact may change considerably our image of aging.