Prospective Memory Efficiency

Much of the research on prospective memory Opens in new window has been concerned with identifying the factors that promote successful remembering or induce failure.

The nature of the prospective task Opens in new window is one of these factors, but other important determinants arise from how the task is encoded and the kind of strategies, reminders, and cues that are used. Meacham and Leiman (1975) gave people postcards to post back at varying intervals up to 32 days later.

Half the subjects were given colored tags to hang on their key chains as a reminder, and there was some evidence that this improved performance. McDaniel and Einstein (1993) have demonstrated that cues that are highly distinctive and specific are most effective.

However, many people spontaneously devise their own reminders. Moscovitch (1982) suggested that the superior performance of the elderly in some prospective memory tasks Opens in new window is due to increasing reliance on external reminders.

Elderly people are known to make more use of written reminders in diaries and notes, and Harris (1980) also reported that middle-aged women made extensive use of reminders such as calendars and wall charts to remember family birthdays and social commitments.

Other people make knots in handkerchiefs, leave objects where the eye will fall on them, or write in biro on their hands. Differences in the extent to which people devise internal and external reminders, and use them efficiently, may underlie observed differences in prospective task performance between individuals, age groups, or sexes.

For a prospective act to be performed, the actor must not only remember to perform it, but also must be willing to perform it. A patient may remember a hospital appointment, but not feel like going, or may remember to take prescribed medication, but decide not take it.

These are examples where poor motivation, rather than a failure of prospective memory Opens in new window, has caused a failure of compliance. But the level of motivation may also affect whether the prospective act is remembered.

It is a truism that very important appointments are rarely missed. When a job interview is make-or-break, you get there on time. A high level of motivation may ensure that an elaborate reminder system is set up and the sequence of events is carefully planned and frequently rehearsed.

These common sense observations have been confirmed experimentally. Meacham and Singer (1977) gave subjects eight postcards to post back one a week for eight weeks.

One group was offered a cash incentive for posting on time, which produced a small improvement in performance.

Poon and Schaffer (1982) asked subjects to phone in 25 times over a 3-week period at specific times. Although a cash incentive had no effect on the proportion of calls remembered, the payment did improve the accuracy of timing for the elderly subjects but not for the young subjects.

The effects of experimental manipulation of motivation by incentives is not very striking, but it seems probable that self-generated motivation in naturally occurring prospective memory tasks is a more powerful factor.

Other factors that are potentially relevant have so far received little attention. These include emotion Opens in new window and personality traits Opens in new window and states such as levels of anxiety and stress, and the effects of fatigue and illness.

Cockburn and Smith (1994), in one of the few studies that have addressed these problems, found a complex relationship between level of anxiety and performance on a prospective memory task.

Their findings suggested that both low and high levels of anxiety can be beneficial, but intermediate levels produce more failures. At this level there is sufficient anxiety to produce errors but not enough to induce the extra effort needed to overcome them.

Searleman and Gaydusek (1989) also reported that people with Type A personalities, who are highly conscientious, tense, competitive worriers, are better at prospective memory tasks.

Another factor that has been studied experimentally is timing. Time factors such as the length of the retention interval, the time of day, and the regularity of target times have been manipulated.

By analogy with retrospective memory Opens in new window, and in line with the proximity effect in Hitch and Ferguson’s (1991, p.28) study of memory for films, it would be expected that prospective memory would decline as the retention interval increased.

However, Wilkins (1976) varied the retention interval in a postcard task from 2 to 36 days, but found no effect of increasing delay. This finding reinforces the view that prospective memory does not operate like retrospective memory.

Harris and Wilkins (1982) studied the effect of response spacing. Subjects were asked to hold up a card at 3- or 9- minute intervals while watching a film. They found no effect of response spacing and no effect of the stage of the film.

The interesting finding in this study was that subjects sometimes forgot to make the response even though they had checked the time within the previous 10 seconds. In this situation, with the competing activity of watching the film, it was difficult to hold prospective intentions in mind even for a very short time.

Everyday life often involves concurrent tasks, and we are often distracted from our prospective intentions as, absorbed in one activity, we forget to interrupt it and do something else.

The amount and type of concurrent activity are likely to be important factors in naturally occurring prospective memory.

Ellis and Nimmo-Smith (1993) noted that their subjects reported more rehearsal of future intentions when their concurrent task required little attention, and common sense suggests that busy people with a lot on their minds might perform differently from those with a more relaxed schedule.

Prospective memory efficiency is also affected by the relationship between goal and action.

Studies that are indirectly relevant to prospective memory were carried out by Lichtenstein and Brewer (1980) and Brewer and Dupree (1983). They were investigating memory for actions that had already been performed, rather than memory for future actions.

They proposed that goal-directed sequences of actions are organized within an overall plan schema. Within the plan schema, the actions are linked by the in-order-to relationship to an overall goal.

In a recall test, actions higher up in the goal hierarchy were remembered better than those lower than, and actions that did not relate directly to the main goal (e.g. putting keys back into pocket) were also less well remembered.

They concluded that plan schemas have a strong influence on recall of actions. Brewer and Dupree, in a further series of experiments, were able to clarify the role of plan schemas.

Their results indicated that, over time, information about actions was progressively lost from the hierarchy in a bottom-up direction, but the plan schema was used to reconstruct the whole action sequence at the retrieval stage.

In everyday life, prospective plans are commonly embedded within each other. For example, my plan to remember to buy some eggs is embedded in a higher-order plan to make a birthday cake.

If prospective plans are like retrospective actions in being better remembered when they are embedded in a plan schema, then experiments on prospective memory may be underestimated everyday ability by using isolated tasks that do not form part of a plan schema.