memory failures

The fallibility of human memory

I don't often talk about eyewitness testimony, but it's not because of the lack of research. It's a big field, with a lot of research done. When  I say I don't follow it because I regard the main finding as a done deal - eyewitness testimony is useless - that's not meant to denigrate the work being done. There is, clearly, a great deal of value in working out the exact parameters of human failures, and in working out how we can improve eyewitness testimony. I just arbitrarily decided to ignore this area of research until they'd sorted it all out!


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Normal is a label too

We all like simple solutions. However much we may believe we are ‘above’ black-&-white dichotomies, that of course we understand that every situation is complex, nevertheless we have a brain that can only think of a very very few things at once. So it's unsurprising that we are drawn to solutions that can be summed up simply, that can fit comfortably within the limitations of working memory.


Mottron, L. (2011). Changing perceptions: The power of autism. Nature. 479(7371), 33 - 3

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Forgetting a skill or procedure

  • Memory for skills — procedural memory — is stored as action sequences, in our unconscious memory.
  • Because this type of memory is very reliable, failures are usually particularly puzzling and even distressing.
  • Because the memory is less accessible, we also tend to have problems dealing with failures.
  • Failures occur when an action sequence becomes disrupted for some reason. When this happens, we have to retrieve the knowledge stored in our conscious memory, that we used when learning the skill.

Have you ever been driving a car and suddenly you’re not sure what to do? You’re traveling along in usual automatic fashion and there comes a moment when you need to engage a new subroutine — say, you need to give way at an intersection, or you stall at the traffic lights, or you stop the car — and suddenly, you don’t know what to do. There’s a flash of panic, even while you’re thinking, “This is stupid, I’ve done this a thousand times”, and then, maybe it’s all right, maybe you have to take a moment to get your head in the right space, and ... okay, you’re off again, control safely in the hands of the automatic pilot.

But you’re unsettled. There are lots of ways our memory fails us. Some of these are very common, so common we just accept them — noone (well, few of us) expect our memories to be 100% perfect all the time. But procedural memory — the memory that allows us to drive a car, ride a bike, type, play the piano, etc — is different from other types of memory. We don’t say “it’s like riding a bicycle” without reason. Once we’ve truly mastered a skill, we expect to have that, for ever. And, for the most part, we do.

The thing about procedural memory — the big difference between it and so-called declarative memory — is that it is not in conscious memory. That’s its huge advantage; we could never perform skills fast enough if they were under conscious control. As we acquire a skill, the declarative information we learn (‘use your little finger on the “a”; the “s” is next to the “a”; the “d” is next to the “s” ’ etc) is transformed into so-called “procedural rules”, which are completely internalized, beyond our conscious manipulation. This greatly reduces the involvement of working memory, and protects the skill from the types of interference that other types of memory are vulnerable to.

It also means that when we do have a failure, we really don’t know how to deal with it. A conscious mental search is not going to retrieve the needed information, because the information we want is not in our accessible database. So what usually happens is that we are forced to default to our backup — the declarative information we encoded during the original learning process. It is this that accounts for the lack of fluency in the subsequent actions; to regain fluency, you must engage the unconscious action sequence.

I don’t know of any research that has looked into these occasional glitches, but I presume that what happens is that the action sequence doesn’t immediately engage. As soon as it doesn’t, we pay attention — that makes it even more likely that the action sequence won’t be triggered, because conscious awareness is precisely what we don’t want.

One piece of research that is relevant to this is a recent study that looked at the phenomenon of “choking” — top athletes performing below par at crucial moments. It’s suggested that the problem lies in part in the athlete paying too much attention to what they’re doing. Skills are the one area of memory where too much attention is deleterious to performance!

I think the best way to deal with this very occasional glitch in performance is to relax, stop thinking about what you’re doing, go back a little in the action sequence to an obvious starting point (if you can’t or don’t need to physically re-do earlier steps, mimic the steps). Remember that skills are stored as sequences, and it’s hard to break in halfway through a sequence, you need to start at the beginning.

You can read more about skill memory and about the best way to practice.

You might also be interested in a related (but separate) issue, that of action slips, which are a product of a lack of attention, not a surfeit.

This article originally appeared in the November 2004 newsletter.

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Forgetting to do things

  • Forgetting future tasks and events is the most common type of memory failure
  • Older adults are in general no worse at this type of remembering than younger adults
  • Older adults may have more difficulty at remembering to do actions at particular times
  • Older adults also need to make more effort in situations when an action cannot be performed immediately, but must be held in memory for a brief period.

The other day I was sitting in the sunshine in my living room going through some journal articles I'd photocopied. I realized I needed to staple the pages together and went down to my study to get the stapler. Approaching my desk, I decided to check my email while I was there. And then, I decided to check my library account online to see whether a book I had requested had turned up. When I'd done that, I went back upstairs to my papers. Where I realized, of course, that I'd forgotten the stapler.

This type of memory failure — going to do something, getting sidetracked, doing something else and forgetting the original task — is familiar to all of us. As are everyday memory failures like forgetting to put the garbage out; forgetting to take medication at the right time; forgetting a dentist appointment (although there's more than one reason for that!).

This type of memory failure — forgetting the future, as it were — is a failure of a type of memory called prospective memory, and it is probably the most common type of memory failure older adults suffer from. And probably the biggest concern.

It's a concern because it's a failure of memory that has consequences, and those consequences are often not only obvious to ourselves, but also to others. Which makes us feel worse, of course.

But it's not just a matter of being embarrassed. Older adults are particularly vulnerable to thoughts that they are "losing" their memory — and the fear of Alzheimer's lurks in all of us.

So, should you be worried if you forget what you're doing?

Like other types of forgetting or absent-mindedness, it depends on the degree of your forgetfulness. But prospective memory failure is common among older adults for a very good reason. Not because it's a precursor of cognitive impairment, but because it's the most common type of memory failure for everyone.

In fact, older adults in general are no worse than anyone else in this particular memory domain, although they may worry about it more (because they worry about any memory failure more).

In some aspects of prospective memory, older adults are actually better than younger adults! One reason for this is that they are more likely to use memory aids — like writing down reminders, or putting reminder objects in strategic places — to help them remember.

However, it does seem that older adults may do less well at remembering things that have to be done at particular times, and one reason for this seems to be that they tend to be poorer at monitoring time. In these cases, it's therefore a good idea to use timers as reminders.

Older adults also seem to have more trouble in the situation when a remembered intention cannot be performed immediately, but must be held in memory for a brief period. Even 5-10 seconds is too long! Tasks that you are "just about" to perform, but in fact are not doing that very second (because you have some other intervening task to do first) are probably particularly dangerous because you don't feel a need to make an effort to remember them (because you are "just about" to do it). But without rehearsal, information falls out of working memory (the stuff we're holding in the conscious "forefront" of our mind) in seconds. So you do need to make an effort. And often, that's all it needs.

You can read more about planning memory strategies in my ebook on planning memory.


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Word-finding problems

  • It is normal for word-finding problems to increase as we age
  • It is normal for us to be slower in processing information as we age
  • Difficulty in retrieving words does not mean the words are lost; there is no evidence that we lose vocabulary in normal aging
  • There is little evidence for any change in semantic structure (the organization of words in memory) with age
  • Older adults probably have more trouble dealing with large amounts of information
  • Older adults may develop different strategies as they age, probably to accommodate their decline in processing speed and processing capacity

What do we mean by word-finding problems?

Here are some examples:

  • increasing use of circumlocutions rather than specific terms (e.g., "I wonder where the thing that goes here is")
  • use of empty phrases, indefinite terms, and pronouns without antecedents (i.e., referring to something or someone as "it" or "him / her" without first identifying them by name)
  • increased frequency of pauses

These problems are all characteristic of Alzheimer's, but also, to a much lesser extent, of normal aging.

Verbal fluency declines with age

Verbal fluency is measured by how many words fitting a specific criteria you can generate in a fixed time (for example, how many types of fruit you can list in a minute).

Verbal fluency often (but not always) declines as we age. This may be partly because older adults are slower to access information.

Tip-of-the-tongue experiences increase with age

There is no evidence that normal older adults actually lose the meanings of words they know.

Older adults do however have more word-finding problems than younger adults. In particular, as we get older we tend to experience more experiences when the word we are searching for is "on the tip of my tongue" [1]. (For more detail about this, see the research report at Burke 1991)

Picture-naming errors also increase, though not perhaps until the eighties [2].

Some studies have found a decline in older adults’ ability to produce words when given their definitions, but others haven’t. This may relate to strategy differences.

No structural changes to memory in normal aging

So, older adults do show some of the same type of word-finding problems as Alzheimers patients do, but to a considerably smaller degree. There is little evidence however that this decline is due to any structural changes in semantic memory with age. Normal younger and older adults give the same sort of responses. (Alzheimers patients on the other hand, become more eccentric in their word associations).

Older adults may tend to use different memory strategies than younger adults

While older adults are slower to make category judgments (e.g., "Is a tomato a fruit? True or false"), they do not give responses different from those of younger adults, supporting the view that semantic organization hasn't changed. However, there is some evidence that young and old differ in the way they judge similarity (older adults seem to rely more on distinctive features; younger adults use both common and distinctive features). This may however be due to strategy differences.

There is no evidence for any decline in prose comprehension with age. However, when there is a large load on memory (when the text is complex, for example), older adults find retrieving general knowledge more difficult.

It appears that encoding of new information might become less context-specific with age, but this may only relate to particular types of context information. It might only be that older adults are less inclined to attend to such (largely irrelevant) details as: whether something was printed in upper or lower case; the sex of a speaker; the color in which a word is printed. The temporal and spatial contexts are also likely to be less important. In other words, older adults seem to encode less information about the source of new information (the circumstances in which the information was acquired) than younger adults.


  • Light, Leah L. The organization of memory in old age. In Craik, Fergus I. M. & Salthouse, Timothy A. (eds). 1992. The Handbook of Aging and Cognition. Hillsdale, NJ: LEA. Pp111-165.
  1. Burke DM, MacKay DG, Worthley JS, & Wade E. 1991. On the tip of the tongue: What causes word finding failures in young and older adults? Journal of Memory and Language, 30, 542-79.
    Cohen G & Faulkner D. 1986. Memory for proper names: Age differences in retrieval. British Journal of Developmental Psychology, 4, 187-97.
  2. Albert MS, Heller HS, & Milberg W. 1988. Changes in naming ability with age. Psychology and Aging, 3, 173-8.
    Borod JC, Goodglass H, & Kaplan E. 1980. Normative data on the Boston Diagnostic Aphasia Examination, Parietal Lobe Battery, and the Boston Naming Test. Journal of Clinical Neuropsychology, 2, 209-15.
    Van Gorp W, Satz P, Kiersch ME & Henry R. 1986. Normative data on the Boston Naming Test for a group of normal older adults. Journal of Clinical and Experimental Neuropsychology, 8, 702-5.
    Mitchell DW. 1989. How many memory systems? Evidence from aging. Journal of Experimental Psychology: Learning, Memory & Cognition, 15, 31-49. (no age effect found).

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Short-Term Memory Problems

  • Short-term memory problems are, by and large, attention problems.
  • Attention involves both the ability to keep focused on the information you want to keep active, and the ability to not be distracted by competing and irrelevant stimuli.
  • You need to actively attend to keep information active, particularly as you get older.
  • Many of us over-estimate how much information we can keep active at one time.

Many people, particularly as they get older, have concerns about short-term memory problems: going to another room to do something and then forgetting why you’re there; deciding to do something, becoming distracted by another task, and then forgetting the original intention; uncertainty about whether you have just performed a routine task; forgetting things you’ve said or done seconds after having said or done them; thinking of something you want to say during a conversation, then forgetting what it was by the time it’s your turn to speak, and so on.

This is clearly an issue for many of us. Part of the reason, I believe, is simply that we expect too much from ourselves. For example, research has shown that even a very, very short delay between recalling an intention and being able to carry it out is sufficient to dramatically reduce the likelihood that you will remember to do the intended action — we are talking about a delay of only 10 seconds!

The problem is exacerbated by age (I’m not talking about advanced age — I’m afraid certain aspects of cognitive processing begin to decline as early as the 30s).

Part of the problem is also that we tend to believe that we don’t need to do anything to maintain a thought, particularly when it has “popped” into our minds easily. But current estimates are that unrehearsed information lingers in working memory for less than two seconds!

Some of these problems are dealt with in my article on action slips (these problems are not, strictly speaking, a failure of memory, but a failure in attention), and in my e-book on Remembering intentions.

But in this article I want to talk about another aspect: the relationship between working memory, and attention (and, as it happens, intelligence!).

In my article on working memory and intelligence I talk about the difference between crystallized and fluid intelligence — that fluid intelligence is probably a better measure of what we think of as “intelligence”, and that working memory capacity is often used synonymously with fluid intelligence. A new theory is that the relationship between working memory and fluid intelligence is due to the ability to control attention.

This theory emphasizes the role of attention in keeping information active (i.e. in working memory), and argues that working memory capacity is not, as usually thought, about the number of items or amount of information that can be held at one time. Instead, it reflects the extent to which a person can control attention, particularly in situations where there is competing information / demands.

I have to say that this makes an awful lot of sense to me. I can’t, in the space I have here, go into all the evidence for and against the theory, but here’s one situation which is interesting. The “cocktail party phenomenon” is a well-known method in psychology, whereby people are given two streams of audio, one for each ear, and instructed to listen only to one. At some point, the person’s name is spoken into the unattended stream, and about a third of people pick that up. In a recent take of that classic study, researchers compared the performance of people as a function of their working memory capacity. Only 20% of those with a high capacity heard their name in the unattended channel compared to 65% of low-capacity people. The point being that a critical aspect of good attentional control is the ability to block our irrelevant information.

This ability is one that we already know is worsened by increasing age.

The message from all this, I guess, is that:

  • short-term memory problems are, by and large, attention problems.
  • attention involves both the ability to keep focused on the information you want to keep active, and the ability to not be distracted by competing and irrelevant stimuli.
  • you need to actively attend to keep information active, particularly as you get older.
  • many of us over-estimate how much information we can keep active at one time.

And if you want strategies to help you keep more information active, I suggest you look at improving your ability to chunk, condense and label information. If you can reduce a chunk of information to a single label quickly, all you need to do is remember the label. (I explain all this at length in my book The Memory Key, but I’m afraid it needs far too much explanation to go into here).

Anyway, I hope this helps those of you (most of us!) with short-term memory problems.

This article originally appeared in the April 2005 newsletter.


Heitz, R.P., Unsworth, N. & Engle, R.W. 2004. Working memory capacity, attention control, and fluid intelligence. In O. Wilhelm & R,W. Engle (eds.) Handbook of Understanding and Measuring Intelligence. London: Sage Publications.

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Everyday memory problems

  • Frequent failures to retrieve information that should be readily accessible can generally be attributed to physical, environmental, and strategic reasons.
  • Physical reasons encompass health problems, lack of sleep, and stress.
  • Environmental reasons mainly concern how distracted you are.
  • Strategic reasons concern a failure to adopt effective memory strategies as situations and abilities change.

I was recently asked for advice in the case of increased “brain blocks” — failures to retrieve information that should be readily accessible. This question is, I suspect, of interest to many of my readers, so I thought I would answer it here.

There are many possible causes for an increase in this type of memory failure. These causes fall into three main categories: physical, environmental, and strategic. Let’s deal with the physical first.

Physical reasons for memory failure

Before looking at applying new strategies or making changes to your environment, you should first rule out the possibility that your memory difficulties are caused by health problems. To do this, you should consider whether memory failure is your sole symptom. If it is (and I have to say, I suspect this will rarely be true), then, fine, go straight to considering your environment and your habits. However, if you have other symptoms, however unrelated, then consider the possibility that your mental problems are part and parcel of some underlying physical dysfunction.

It may be something as simple as lack of sleep. In fact, considering how widespread the modern trend of not getting enough sleep is, I’d say look at that first. Don’t underestimate the importance of sleep in ensuring your brain is firing on all cylinders.

After sleep, I suggest you look at the other modern disease: allergies / sensitivities of various kinds. (I am assuming you don’t have a major health problem — presumably you would already be aware of this). If you suffer from these, you will have a raft of symptoms, possibly minor, but startling in their array if you stop and think about them.

For example, in my own case, I first considered food sensitivities because of serious fatigue. However, once I found the major offender (wheat), and realized that, indeed, food sensitivity was to blame, I listed all the various things “wrong” with me — things I was used to, that I just thought were how I was, such as achy joints. I filled a page with such ailments! (And, yes, to my complete astonishment, after having achy joints most of my life, I no longer get them now that I know the offending foods). My point is that if you’re suffering from food or chemical sensitivities, you will almost certainly suffer from multiple symptoms.

And, of course, the final modern disease is that old bugbear, stress.

I think it’s fair to say that adequate sleep, adequate exercise, and appropriate diet will ameliorate most of the “minor” physical ailments that impede memory (I hasten to add that I’m using “minor” only to distinguish such complaints from major disorders that require medical intervention).

I’m not saying that ensuring you eat right, sleep well, and exercise sufficiently, is easy! But don’t expect these things not to affect you, particularly as you age (and we’re not talking serious age, here; even in your thirties, you can’t get away with the complete disregard you may have shown in your twenties).

So much for physical causes. What about the environment?

Environmental reasons for memory failure

If you’re madly busy, if you’re having to keep many different things in mind, then you must expect this to take its toll on your mental resources, especially as you age. Don’t compare yourself to others — we are all different, and all have different capacities. Some people thrive on situations that would send another person to a hospital bed. You know yourself if you feel too stretched, if you’re juggling too many things, have too many responsibilities or too many people looking to you ... Don’t go by what you think you ought to be able to manage, go by what you can manage.

Strategic reasons for memory failure

And then there’s strategies. What you do to manage your life, your tasks, your memory needs. Most of us developed strategies for dealing with these matters early in life, when our mental and physical abilities were at their peak, when we had fewer complications in our lives. When these strategies begin to fail, most of us blame ourselves — that there is something “wrong” with us. In most cases, however, the fault is simply that the strategies were not particularly good ones. We got away with using them because we did not, at that point in our lives, require particularly effective strategies. Now we do. Accept that, and move on.

What to do

So, my advice to those of you suffering from this type of forgetfulness is to first consider whether your health is compromised or your capacities too stretched. Secondly (and whether or not these conditions are true), look for strategies that will relieve some of the burdens on your memory. Remember that, in today’s world, most of us put far more demands on our memory than has been the case at any previous point in human history. So don’t be afraid to use external aids to memory. Design your life, and build routines, that minimize the demands on your memory as best you can. And never take for granted that you will remember anything that you have made no deliberate attempt to remember.

You can find more specific advice for specific memory problems at:

Action Slips

Short-Term Memory Problems

Word-finding problems

Tip-of-the-tongue experiences

Multitasking problems

Forgetting a skill or procedure

This article originally appeared in the June 2004 newsletter.

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