working memory

Meditation's cognitive benefits

A critical part of attention (and working memory capacity) is being able to ignore distraction. There has been growing evidence that meditation training (in particular mindfulness meditation) helps develop attentional control, and that this can start to happen very quickly.

For example:

  • after an eight-week course that included up to 30 minutes of daily meditation, novices improved their ability to quickly and accurately move and focus attention.
  • three months of rigorous training in Vipassana meditation improved attentional control.
  • after eight weeks of Mindfulness Training, Marine reservists during pre-deployment showed increased working memory capacity and decreased negative mood (this training also included concrete applications for the operational environment and information and skills about stress, trauma and resilience in the body).
  • after a mere four sessions of 20 minutes, students produced a significant improvement in critical cognitive skills — and a dramatic improvement when conditions became more stressful (provided by increasingly challenging time-constraints).

There seem to be several factors involved in these improvements: better control of brainwaves; increased gray matter density in some brain regions; improved white-matter connectivity.

Thus, after ten weeks of Transcendental Meditation (TM) practice, students showed significant changes in brainwave patterns during meditation compared to eyes-closed rest for the controls. These changes reflected greater coherence and power in brainwave activity in areas that overlap with the default mode network (the brain’s ‘resting state’). Similarly, after an eight-week mindfulness meditation program, participants had better control of alpha brainwaves. Relatedly, perhaps, experienced Zen meditators have shown that, after interruptions designed to mimic spontaneous thoughts, they could bring activity in most regions of the default mode network back to baseline faster than non-meditators.

Thus, after an 8-week mindfulness meditation program, participants showed increased grey-matter density in the left hippocampus , posterior cingulate cortex, temporo-parietal junction , and cerebellum , as well as decreased grey-matter density in the amygdala . Similarly, another study found experienced meditators showed significantly larger volumes of the right hippocampus and the right orbitofrontal cortex, and to a lesser extent the right thalamus and the left inferior temporal gyrus.

These areas of the brain are all closely linked to emotion, and may explain meditators' improved ability in regulating their emotions.

Thus, long-term meditators showed pronounced differences in white-matter connectivity between their brains and those of age-matched controls, meaning that meditators’ brains were better able to quickly relay electrical signals. The brain regions linked by these white-matter tracts include many of those mentioned as showing increased gray matter density. Another study found that a mere 11 hours of meditation training (IBMT) produced measurable changes in the integrity and efficiency of white matter in the corona radiata (which links to the anterior cingulate cortex, an area where attention and emotion are thought to be integrated).

It’s an interesting question, the extent to which poor attentional control is a reflection of poor emotional regulation. Obviously there is more to distractability than that, but emotion and attention are clearly inextricably entwined. So, for example, a pilot study involving 10 middle school students with ADHD found that those who participated in twice-daily 10 minute sessions of Transcendental Meditation for three months showed a dramatic reduction in stress and anxiety and improvements in ADHD symptoms and executive function.

The effects of emotion regulation are of course wider than the effects on attention. Another domain they impact is that of decision-making. A study involving experienced Buddhist meditators found that they used different brain regions than controls when making decisions in a ‘fairness’ game. The differences reflected less input from emotional reactions and more emphasis on the actual benefits.

Similarly, brain scans taken while experienced and novice meditators meditated found that periodic bursts of disturbing noise had less effect on brain areas involved in emotion and decision-making for experienced meditators compared to novices — and very experienced meditators (at least 40,000 hours of experience) showed hardly any activity in these areas at all.

Attention is also entwined with perception, so it’s also interesting to observe that several studies have found improved visual perception attendant on meditation training and/or experience. Thus, participants attending a three-month meditation retreat, showed significant improvements in making fine visual distinctions, and ability to sustain attention.

But such benefits may depend on the style of meditation. A study involving experienced practitioners of two styles of meditation (Deity Yoga (DY) and Open Presence (OP)) found that DY meditators were dramatically better at mental rotation and visual memory tasks compared to OP practitioners and controls (and only if they were given the tasks immediately after meditating). Similarly, a study involving Tibetan Buddhist monks found that, during "one-point" meditation, monks were significantly better at maintaining their focus on one image, when two different images were presented to each eye. This superior attentional control was not found during compassion-oriented meditation. However, even under normal conditions the monks showed longer stable perception compared to meditation-naïve control subjects. And three months of intense training in Vipassana meditation produced an improvement in the ability of participants to detect the second of two visual signals half a second apart (the size of the improvement was linked to reduced brain activity to the first target — which was still detected with the same level of accuracy). Similarly, three months of intensive meditation training reduced variability in attentional processing of target tones.


You can read about these studies in more detail in the aggregated news reports on meditation. Three studies were mentioned here without having appeared in the news reports:

Lutz, A., Slagter, H. A., Rawlings, N. B., Francis, A. D., Greischar, L. L., & Davidson, R. J. (2009). Mental Training Enhances Attentional Stability: Neural and Behavioral Evidence. J. Neurosci., 29(42), 13418-13427. doi:10.1523/JNEUROSCI.1614-09.2009

Tang, Y.-Y., Lu, Q., Geng, X., Stein, E. A., Yang, Y., & Posner, M. I. (2010). Short-term meditation induces white matter changes in the anterior cingulate. Proceedings of the National Academy of Sciences, 107(35), 15649 -15652. doi:10.1073/pnas.1011043107

Travis, F., Haaga, D., Hagelin, J., Tanner, M., Arenander, A., Nidich, S., Gaylord-King, C., et al. (2010). A self-referential default brain state: patterns of coherence, power, and eLORETA sources during eyes-closed rest and Transcendental Meditation practice. Cognitive Processing, 11(1), 21-30. doi:10.1007/s10339-009-0343-2



Effect of working memory capacity on new language learning

Vocabulary acquisition in children is significantly affected by the child's ability to repeat back words.

This limitation becomes less as the individual gains a large vocabulary, and thus develops a greater ability to make semantic (meaningful) associations.

When learning a new language, your ability to repeat back unfamiliar words is only a factor where you are unable to form a meaningful association to a familiar word.

In such cases, the keyword mnemonic can be especially useful to those with limited ability to repeat back words.

Research with children has demonstrated that the ability to learn new words is greatly affected by working memory span - specifically, by how much information they can hold in that part of working memory called "phonological short-term memory". The constraining effect of working memory capacity on the ability to learn new words appears to continue into adolescence.

But, as you grow in experience, building a vocabulary, this constraint becomes less important. Because working memory capacity is measured in "chunks" - and the amount of information contained in a chunk is extremely malleable. To a large extent, developing chunking strategies is what memory improvement is all about.

In terms of learning another language, there are essentially four possible classes of word:

  • words that are already familiar because they are the same in your native language (or another known language)
  • words that are already familiar because they involve words that you already know in that language (e.g., learning a related verb form, or learning a word made up of two words you already know, such as sweat-shirt)
  • words that resemble a known word with similar or related meaning (e.g., Russian garlo means throat, and the word garlo resembles the word gargle)
  • words that have no ready association to known words

It appears that in these first three cases, the size of your phonological short-term memory is of no significant relevance. It is only in the last case - where the word cannot utilize any meaningful associations - that your phonological short-term memory capacity becomes important.

Fairly obviously, as your knowledge of language (your own and others) grows, the more meaningful associations you will be able to make, and the fewer new words will fall into this last, difficult, category.

This suggests, of course, the usefulness of a mnemonic strategy (specifically, the keyword strategy) in the last, difficult case.

The importance of phonological short-term memory is also greater for productive learning (learning to produce a language, i.e., speak or write it) than in receptive learning (learning to read or understand a language). For productive learning, the pronounceability of the new words is very important. The more easily pronounced, the more easily learnt.

  • Nation, I.S.P. 2001. Learning vocabulary in another language. Cambridge: Cambridge University Press.
  • Ellis, N.C. & Beaton, A. 1993. Factors affecting foreign language vocabulary: imagery keyword mediators and phonological short-term memory. Quarterly Journal of Experimental Psychology, 46A, 533-58.
  • Papagno, C., Valentine, T. & Baddeley, A. 1991. Phonological short-term memory and foreign-language vocabulary learning. Journal of Memory and Language, 30, 331-47.

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.

  1. 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.

Working Memory and Intelligence

Intelligence tends nowadays to be separated into 2 components: fluid intelligence and crystallized intelligence.

Fluid intelligence refers to general reasoning and problem-solving functions, and is often described as executive function, or working memory capacity.

Crystallized intelligence refers to cognitive functions associated with knowledge.

Different IQ tests measure fluid intelligence and crystallized intelligence to varying extents, but the most common disproportionately measures crystallized intelligence.

Increasing evidence suggests that even fluid intelligence is significantly affected by environmental factors and emotions.

You may have heard of “g”. It’s the closest we’ve come to that elusive attribute known as “intelligence”, but it is in fact a psychometric construct, that is, we surmise its presence from the way in which scores on various cognitive tests positively correlate.

In other words, we don’t really know what it is (hence the fact it is called “g”, rather than something more intelligible), and in fact, it is wrong to think of it as a thing. What it is, is a manifestation of some property or properties of the brain — and we don’t know what these are.

Various properties have been suggested, of course. Speed of processing; synaptic plasticity; fluid cognition. These are all plausible, but experimental studies have failed to provide clear evidence for any of them. The closest has been fluid cognition, or fluid intelligence, which is paired with crystallized intelligence. These two terms point to a useful distinction.

Fluid intelligence refers to cognitive functions associated with general reasoning and problem-solving, and is often described as executive function, or working memory capacity.

Crystallized intelligence, on the other hand, refers to cognitive functions associated with previously acquired knowledge in long-term store.

There is of course some interplay between these functions, but for the most part they are experimentally separable.

There are a couple of points worth noting.

For a start, different IQ tests measure fluid intelligence and crystallized intelligence to varying extents – the Raven’s Progressive Matrices Test, for example, predominantly measures fluid intelligence, while the WAIS disproportionately measures crystallized intelligence. An analysis of the most widely used intelligence test batteries for children found that about 1/3 of the subtests measure crystallized intelligence, an additional ¼ measure knowledge and reading/writing skills, while only 7% directly measure fluid intelligence, with perhaps another 10% measuring skills that have a fluid intelligence component – and nearly all the fluid subtests were found in one particular test battery, the W-J-R.

The so-called Flynn effect – the rapid rise in IQ over the past century – is for the most part an increase in fluid intelligence, not crystallized intelligence. While it has been hypothesized that fluid intelligence paves the way for the development of crystallized intelligence, it should be noted that the distinction between fluid and crystallized intelligence is present from a very early age, and the two functions have quite different growth patterns over the life of an individual.

So, what we’re saying is that most IQ tests provide little measure of fluid intelligence, although fluid intelligence appears to reflect “g” more closely than any other attribute, and that although crystallized intelligence is assumed to reflect environment (e.g., education) far more than fluid intelligence, it is fluid intelligence that has been rising, not crystallized intelligence.

In fact, for this and other reasons, it seems that fluid intelligence is far more affected by environment than has been considered.

I’ll leave you to ponder on the implications of this. Let me make just one more point.

The brain areas known to be important for fluid cognition are part of an interconnected system associated with emotion and stress response, and it is hypothesized that functions heretofore considered distinct from emotional arousal, such as reasoning and planning, are in fact very much part of a system in which emotional response is involved.

We’re not saying here that emotions can disrupt your reasoning processes, we all know that. What is being suggested is more radical – that emotions are part and parcel of the reasoning process. Okay, I always knew this, but it’s nice to see science coming along and providing some evidence.

The point about the close interaction between emotional reactivity and fluid intelligence is that stress may have a significant effect on fluid intelligence.

And I’ll leave you to ponder the implications of that.

This article originally appeared in the March 2005 newsletter.


Miyake, A., Friedman, N.P., Rettinger, D.A., Shah, P., & Hegarty, M. 2001. How are Visuospatial Working Memory, Executive Functioning, and Spatial Abilities Related? A Latent-Variable Analysis. Journal of Experimental Psychology – General, 130(4).

Working memory

Working memory is one of the most important concepts in understanding and improving your memory.

Your working memory capacity is a critical factor in determining your ability to :

  • take good notes,
  • read efficiently,
  • understand complex issues,
  • reason.

Indeed it may be that it is your working memory capacity that best ‘measures’ your intelligence.

Short-term vs long-term memory

Working memory is a relatively recent term, a refinement of an older concept - that of short-term memory. Short-term memory was called thus to distinguish it from "long-term memory" - your memory store.

One important difference between the idea of short-term memory and working memory, is that short-term memory was conceived of as a thing. Different from long-term memory (variously analogized as a library, a filing system, a computer) chiefly in the duration of the records it held. But working memory, as its name suggests, is now conceived more as a process than a thing. A state of mind. A pattern of activation.

Working memory contains the information of which you are immediately aware.

To put information into our memory store, it must ... be worked on - i.e., be held in working memory. To get information out of the memory store - to “remember” something - it must again be in an active state - be in working memory. How can we know what we remember if we're not conscious of it?

However, you can only keep something "active" for a very short time without your conscious attention. It is this which so limits working memory capacity.

The magic number seven

Probably the most widely known fact about working memory is that it can only hold around seven chunks of information (between 5 and 9). However, this tells us little about the limits of working memory because the size of a chunk is indeterminate.

1 2 3 4 5 6 7 are seven different chunks - if you remember each digit separately (as you would, for example, if you were not familiar with the digits - as a young child isn't). But for those of us who are only too well-versed in our numbers, 1 through to 7 could be a single chunk.

Recent research suggests however, that it is not so much the number of chunks that is important. What may be important may be how long it takes you to say the words (information is usually held in working memory in the form of an acoustic - sound-based - code). It appears that you can only hold in working memory what you can say in 1.5 — 2 seconds. Slow speakers are therefore penalized.

Your working memory capacity

What we term "working memory" contains several functions, including the "central executive" which coordinates and manages the various tasks needed. The extent to which working memory is domain-specific (different "working memories", if you like, for different sensory and cognitive systems, such as language, spatial memory, number) is still very much debated. However, at a practical level, we may think of working memory as containing several different components, for which you have different "capacities". Thus, your capacity for numbers may well be quite different from your capacity for words, and both from your capacity for visual images.

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Attention warps memory space

screenshot semantic space

A recent study reveals that when we focus on searching for something, regions across the brain are pulled into the search. The study sheds light on how attention works.

In the experiments, brain activity was recorded as participants searched for people or vehicles in movie clips. Computational models showed how each of the roughly 50,000 locations near the cortex responded to each of the 935 categories of objects and actions seen in the movie clips.

Forgetfulness in old age may be related to changes in retrieval strategy

A study of younger and older adults indicates that memory search tends to decline with age because, with reduced cognitive control, seniors’ minds tend to ‘flit’ too quickly from one information cluster to another.

Evidence is accumulating that age-related cognitive decline is rooted in three related factors: processing speed slows down (because of myelin degradation); the ability to inhibit distractions becomes impaired; working memory capacity is reduced.

A new study adds to this evidence by looking at one particular aspect of age-related cognitive decline: memory search.

The study put 185 adults aged 29-99 (average age 67) through three cognitive tests: a vocabulary test, digit span (a working memory test), and the animal fluency test, in which you name as many animals as you can in one minute.

Typically, in the animal fluency test, people move through semantic categories such as ‘pets’, ‘big cats’, and so on. The best performers are those who move from category to category with optimal timing — i.e., at the point where the category has been sufficiently exhausted that efforts would be better spent on a new one.

Participants recalled on average 17 animal names, with a range from 5 to 33. While there was a decline with age, it wasn’t particularly marked until the 80s (an average of 18.3 for those in their 30s, 17.5 for those in their 60s, 16.5 for the 70s, 12.8 for the 80s, and 10 for the 90s). Digit span did show a decline, but it was not significant (from 17.5 down to 15.3), while vocabulary (consistent with previous research) showed no decline with age.

But all this is by the by — the nub of the experiment was to discover how individuals were searching their memory. This required a quite complicated analysis, which I will not go into, except to mention two important distinctions. The first is between:

  • global context cue: activates each item in the active category according to how strong it is (how frequently it has been recalled in the past);
  • local context cue: activates each item in relation to its semantic similarity to the previous item recalled.

A further distinction was made between static and dynamic processes: in dynamic models, it is assumed the user switches between local and global search. This, it is further assumed, is because memory is ‘patchy’ – that is, information is represented in clusters. Within a cluster, we use local cues, but to move from one cluster to another, we use global cues.

The point of all this was to determine whether age-related decline in memory search has to do with:

  • Reduced processing speed,
  • Persisting too long on categories, or
  • Inability to maintain focus on local cues (this would relate it back to the inhibition deficit).

By modeling the exact recall patterns, the researchers ascertained that the recall process is indeed dynamic, although the points of transition are not clearly understood. The number of transitions from one cluster to another was negatively correlated with age; it was also strongly positively correlated with performance (number of items recalled). Digit span, assumed to measure ‘cognitive control’, was also negatively correlated with number of transitions, but, as I said, was not significantly correlated with age.

In other words, it appears that there is a qualitative change with age, that increasing age is correlated with increased switching, and reduced cognitive control is behind this — although it doesn’t explain it all (perhaps because we’re still not able to fully measure cognitive control).

At a practical level, the message is that memory search may become less efficient because, as people age, they tend to change categories too frequently, before they have exhausted their full potential. While this may well be a consequence of reduced cognitive control, it seems likely (to me at least) that making a deliberate effort to fight the tendency to move on too quickly will pay dividends for older adults who want to improve their memory retrieval abilities.

Nor is this restricted to older adults — since age appears to be primarily affecting performance through its effects on cognitive control, it is likely that this applies to those with reduced working memory capacity, of any age.


[3378] Hills, T. T., Mata R., Wilke A., & Samanez-Larkin G. R. (2013).  Mechanisms of Age-Related Decline in Memory Search Across the Adult Life Span. Developmental Psychology. No - Pagination Specified.

A defense of working memory training

Cogmed screenshot

There’s been a certain amount of criticism of working memory training recently. Scott Barry Kaufman in the Scientific American has put out an excellent article critiquing the criticism. Among his points (most of which I have previously made), he notes:

These nuanced effects suggest that personal characteristics should be taken into account when considering the effectiveness of cognitive training. …

Learning Facebook may keep seniors sharp

A really old computer!

Preliminary findings from a small study show that older adults, after learning to use Facebook, performed about 25% better on tasks designed to measure their ability to continuously monitor and to quickly add or delete the contents of their working memory (updating).

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