Problems

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.

References: 

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

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Even mild head injuries can seriously affect the brain

Traumatic brain injury is the biggest killer of young adults and children in the U.S., and in a year more Americans suffer a TBI than are diagnosed with breast, lung, prostate, brain and colon cancer combined. There are many causes of TBI, but one of the more preventable is that of sports concussion.

References: 

References (and more details) for the studies I have mentioned can be found in my topic collection on TBI.

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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.

References: 

  • 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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Tip-of-the-tongue experiences

  • In a tip-of-the-tongue experience, you typically know quite a lot of information about the target word without being able to remember the word itself.
  • Remembering often occurs sometime later, when you have stopped searching for the word.
  • Often a similar sounding word seems to block your recall, but these probably don't cause your difficulty in remembering.
  • TOTs probably occur because of there is a weak connection between the meaning and the sound of a word.
  • Connections are weak when they haven't been used frequently or recently
  • Aging may also weaken connections.
  • TOTs do occur more frequently as we age.
  • In general, this increase in TOTs with age is seen in poorer recall of names (proper names and names of things). Abstract words do not become harder to recall with age.
  • Keeping your experience of language diverse (e.g., playing scrabble, doing crosswords) may help reduce TOTs.

What is a tip-of-the-tongue experience?

The tip-of-the-tongue experience (TOT) is characterized by being able to retrieve quite a lot of information about the target word without being able to retrieve the word itself. You know the meaning of the word. You may know how many syllables the word has, or its initial sound or letter. But you can’t retrieve it all. The experience is coupled with a strong feeling (this is the frustrating part) that you know the word, and that it is hovering on the edges of your thought.

When you do eventually remember it, the experience is often as erratic and abrupt as the initial failure — typically it pops up sometime later, when you have stopped searching for it.

Another characteristic of TOTs is that a similar sounding word keeps blocking the way. There you are, trying to remember Velcro, and all you can think of is helmet. You feel strongly that if you could just stop thinking of helmet, then you’d find the word you’re looking for, but helmet won’t budge.

What causes TOTs?

It has been thought that these interfering words cause the TOTs, but some researchers now believe they’re a consequence rather than a cause. Because you have part of the sounds of the word you’re searching for, your hard-working brain, searching for words that have those sounds, keeps coming up with the same, wrong, words.

A recent study by Dr Lori James of the University of California and Dr Deborah Burke of Pomona College suggests a different cause.

How are words held in memory? A lot of emphasis has been placed on the importance of semantic information — the meaning of words. But it may be that the sound of a word is as important as its meaning.

Words contain several types of information, including:

  • semantic information (meaning),
  • lexical information (letters), and
  • phonological information (sound).

These types of information are held in separate parts of memory. They are connected of course, so that when, for example, you read Velcro, the letter information triggers the connected sound information and the connected meaning information, telling you how to pronounce the word and what it means.

When you try to think of a word, as opposed to being given it, you generally start with the meaning (“that sticky stuff that has fuzz on one side and tiny hooks on the other”). If the connection between that meaning and the sound information is not strong enough, the sound information won’t be activated strongly enough to allow you to retrieve all of it.

Drs James and Burke think that TOTs occur because of weak connections between the meaning and the sound of a word.

Connections are strengthened when they’re used a lot. They are also stronger when they’ve just been used. If you haven’t used a connection for a while, it will weaken. It may also be that aging weakens connections.

This may explain why the errant word suddenly “pops up”. It may be that you have experienced a similar sound to the target word.

Are TOTs worth worrying about?

TOTs are ranked by older adults as their most annoying memory failure. They do happen more often as you age, and this increase starts as early as the mid-thirties.

While everyone has TOTs, there are some differences in the TOTs experienced by older adults. For example, the most common type of word involved in TOTs at all ages is proper names. But while forgetting proper names and object names becomes more common as we get older, abstract words are actually forgotten less.

The length of time before the missing word is recalled also increases with age. This may be because older people are less likely to actively pursue a missing word, and more inclined to simply relax and think about something else. Older adults are also more likely than younger adults to go completely blank (unable to recall any part of the word’s sound or letters).

Alzheimer’s disease is characterized by word failures. However, normal TOTs tend to involve rarely used words. In Alzheimer’s, people lose very high frequency words, such as fork and spoon.

Why do TOTs increase as we age? Part of the reason may be that most of us experience fewer new and rare words as we get older and stuck in our own particular ruts. It seems that we need a lot of activation of the sound connections to keep them alive. The more we limit our experience to the tried and true, the less opportunity to keep these rarer connections active.

Dr James suggests: "People should keep using language, keep reading, keep doing crosswords. The more you use your language and encounter new words, the better your chances are going to be of maintaining those words, both in comprehension and in production, as you get older."

References: 

  • Burke, D.M., MacKay, D.G., Worthley, J.S. & 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, 542-579.
  • James, L.E. & Burke, D.M. 2001. Phonological Priming Effects on Word Retrieval and Tip-of-the-Tongue Experiences in Young and Older Adults. Journal of Experimental Psychology: Learning, Memory and Cognition, 26 (6), 1378-1391.

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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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