Prospective vs. Retrospective Memory

As Neisser observed, ordinary language employs the word remember Opens in new window to reflect at least two different temporal perspectives:

1. “remembering what we must do” or our future plans and
2. “remembering what we have done” or events from the past (Neisser, 1982, p. 327).

The former is termed prospective Opens in new window, and the latter, retrospective remembering Opens in new window, following Meacham and Leiman (1976).

Separating Prospective Memory from Retrospective Memory

Most times when we think about forgetting, we may think of the time we forgot someone’s name, forgot an answer to a test, or forgot the location of a friend’s house. Such examples are common errors of restrospective memory Opens in new window (being memory for past events).

By contrast, when some people think about forgetting Opens in new window, they may lament their ‘to-do list’ items that went unchecked, such as forgetting to buy a card for a family member’s birthday, forgetting to order a medication refill, or forgetting an approaching deadline for a writing assignment.

When someone fails to remember to perform such intended actions in the future, they are experiencing a disorder of prospective memory Opens in new window.

The failure of memory that caused me the most pain was the time I forgot to pick up my 3-year-old son and his friends after nursery school and take them to their play group. Eugene Winogard, Practical Aspects of Memory

This poignant example refers to an aspect of prospective memory.

Even minimal reflection prompts the realization that the texture of our daily existence is inextricably bound with prospective memory tasks.

These task include mundane demands such as:

• remembering to pick up bread on your way home,
• remembering to mail the letter in your briefcase,
• remembering to give your house-mate the message that a friend called,
• remembering to load your bicycle into the car for a ride after work, and so on and so forth.

Prospective memory tasks are integrated into our work lives:

• The waiter must remember to pick up extra cream for a table on his way back to the kitchen, and
• an instructor has to remember to make sure the reserve readings for her class are available before meeting her seminar.

Prospective memory is also involved in activities that are critical to maintaining life. Remembering to take medication is a common example.

Failure to remember to check the backseat of the car after an appropriate period of time has elapsed has produced tragic deaths for young children left in the car.

By comparison:

Prospective memory Opens in new window includes all other types of memory including episodic Opens in new window, semantic Opens in new window and procedural Opens in new window. It can be either declarative Opens in new window (also called explicit) or nondeclarative Opens in new window (sometimes called implicit).

Most generally, one might think of almost all everyday tasks and all laboratory experimental tasks as having both retrospective memory and prospective memory components.

To perform an intended activity, one must remember Opens in new window to recall there was an intention (the prospective component) and also remember the contents of the intention (the retrospective component) (Einstein & McDaniel, 1996).

In everyday contexts, both memory components can be challenged.

In the laboratory, however, one component can be minimized so as to isolate the other component for study. The study of memory Opens in new window has historically emphasized tasks in which the prospective memory component is not challenging and the retrospective component is.

The subject in a typical experiment does not have to remember to recall an intention to remember the studied items because the experimenter explicitly tells the subject to remember.

In Tulving’s (1983) terms, the memory experiment places the subject in a retrieval mode. The study of prospective memory changes this emphasis by focusing on the prospective component and minimizing focus on the retrospective component.

In a retrospective memory Opens in new window experiment, the challenge for the subject is to remember the contents (recall the list of words studied).

The parameters of laboratory retrospective memory tasks ensure that remembering the contents is challenging, so as to reveal the properties, processes, and dynamics of memory.

If we decide to present one word for study and a short time later ask someone to recall that word, all of us would agree that this a retrospective memory task. But this task likely would not tell us much about retrospective memory.

In a similar vein, prospective memory tasks are designed to challenge remembering to recall (whereas the contents to recall are simplified).

Whereas externally prompted retrieval is typically a critical feature of retrospective memory Opens in new window, prospective memory Opens in new window is more often characterized by self-initiated retrieval processes which can make them more vulnerable to forgetting (Craik, 1986).

Other Findings

Baddeley and Wilkins (1984) have pointed out that, in practice, the distinction between the two kinds of memory is not absolutely clear-cut because, as we’ve seen, prospective memory Opens in new window necessarily includes some elements of retrospective memory Opens in new window.

In remembering Opens in new window my plan to phone my mother, I also remember, retrospectively, her number and how to use the phone, and not to call while she is watching her favorite television program. However, despite this overlap between the two kinds of memory, there are numerous distinguishing features (West, 1984).

Prospective memory differs from retrospective memory at the encoding stage, as prospective plans are usually self-generated and do not involve initial learning, but the difference between the two is perhaps more marked at the retrieval stage.

In prospective memory Opens in new window, the amount of information that has to be remembered is usually small. You need only remember to post the letter, call the plumber, or whatever.

In most retrospective memory tasks the amount of information that has to be recalled is much greater. Some studies have also shown that prospective memory ability and retrospective memory ability show signs of dissociation.

Kvavilashvili (1987) found no significant correlation between retrospective and prospective memory. In her study those subjects who were good at the prospective task of remembering to give a message to the experimenter were necessarily good at recalling the content of the message, and vice versa.

Wilkins and Baddeley (1978) actually found a negative correlation. They designed a prospective memory study to simulate remembering to take pills at a specific time. Subjects had to press a button on a small box at 8.30 a.m., 1.00 p.m., 5.30 p.m. and 10 p.m. each day for 7 days. The apparatus in the box recorded the time of each button press.

Lateness of response increased across the 7 days, and across each day, with early responses being more accurate than later ones, perhaps because, later in the day, competing activities were distracting.

The same subjects were also given a retrospective memory test of free recall of lists of unrelated words. It emerged that those who had good retrospective verbal memory did poorly the prospective task, a phenomenon labeled the absentminded professor effect Opens in new window. The same evidence of dissociation is also evident in studies of the effects of ageing on memory.

Although there are logical and functional differences between prospective and retrospective memory, it is by no means clear that prospective memory is a distinct and separate memory system.

It is not too surprising that prospective memory for taking medicine does not correlate strongly with the kind of retrospective memory involved in recall of word lists from long-term memory because these are very different tasks.

When the tasks are more similar a different result emerges.

Hitch and Ferguson (1991) compared prospective and retrospective memory in a study that tested the ability of members of a film society to recall, retrospectively, the names of films they had seen in the past and to recall, prospectively, the names of films they intended to see in the future.

The two kinds of memory showed interesting correspondences. Retrospective memory for past films showed the usual recency effect with better recall of more recent films. Prospective memory for future films showed an analogous proximity effect. Films that would be seen sooner were better remembered.

For both past and future films, memory was inversely related to the total number of films and there was a small but significant correlation between an individual’s retrospective and prospective memory. It is still not clear, therefore, how far prospective memory should be regarded as a distinct and separate memory system.