working memory

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.

References: 

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).

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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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For more, see the research reports

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Picture overload hurts preschooler's word learning

  • A study has found that having more than one illustration results in poorer word learning among pre-schoolers — but this can be mitigated if the reader draws the pre-schooler’s attention to each illustration.

When you're reading a picture book to a very young child, it's easy to think it's obvious what picture, or part of a picture, is being talked about. But you know what all the words mean. It's not so easy when some of the words are new to you, and the open pages have more than one picture. A recent study has looked at the effect on word learning of having one vs two illustrations on a 2-page open spread.

The study, in two experiments, involved the child being read to from a 10-page storybook, which included two novel objects, mentioned four times, but only incidentally. In the first experiment, 36 preschoolers (average age 3.5 years) were randomly assigned to one of three conditions:

  • one illustration (the illustration filled the page, with the text written as part of the illustration, and the opposing page blank)
  • two illustrations (each illustration filled its page, on opposing pages)
  • one large illustration (the page was twice the size of that found in the other conditions) — this was the control condition.

Children who were read stories with only one illustration at a time learned twice as many words as children who were read stories with two or more illustrations. There was no difference in reading time, or in the child’s enjoyment of the story.

In a follow-up experiment, 12 preschoolers were shown the two-illustration books only, but this time the reader used a simple hand swipe gesture to indicate the correct illustration before the page was read to them. With this help, the children learned best of all.

In fact, the rate of word learning in this last condition was comparable to that observed in other studies using techniques such as pointing or asking questions. Asking questions is decidedly better than simply reading without comment, and yet this simple gesture was enough to match that level of learning.

Other studies have shown that various distractions added to picture books, like flaps to lift, reduce learning. All this is best understood in terms of cognitive load. The most interesting thing about this study is that it took so little to ameliorate the extra load imposed by the two illustrations.

https://www.eurekalert.org/pub_releases/2017-06/uos-poh063017.php

https://www.eurekalert.org/pub_releases/2017-07/w-tno071217.php

Also see https://blogs.sussex.ac.uk/psychology/2016/10/24/how-storybook-illustrat... for a blog post by one of the researchers

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Physical activity linked to better memory for names and faces among older adults

  • A small study adds to evidence that walking improves memory in older adults, and indicates that this is particularly helpful for memory tasks the seniors find challenging.

A small study that fitted 29 young adults (18-31) and 31 older adults (55-82) with a device that recorded steps taken and the vigor and speed with which they were made, has found that those older adults with a higher step rate performed better on memory tasks than those who were more sedentary. There was no such effect seen among the younger adults.

Improved memory was found for both visual and episodic memory, and was strongest with the episodic memory task. This required recalling which name went with a person's face — an everyday task that older adults often have difficulty with.

However, the effect on visual memory had more to do with time spent sedentary than step rate. With the face-name task, both time spent sedentary and step rate were significant factors, and both factors had a greater effect than they had on visual memory.

Depression and hypertension were both adjusted for in the analysis.

There was no significant difference in executive function related to physical activity, although previous studies have found an effect. Less surprisingly, there was also no significant effect on verbal memory.

Both findings might be explained in terms of cognitive demand. The evidence suggests that the effect of physical exercise is only seen when the task is sufficiently cognitively demanding. No surprise that verbal memory (which tends to be much less affected by age) didn't meet that challenge, but interestingly, the older adults in this study were also less impaired on executive function than on visual memory. This is unusual, and reminds us that, especially with small studies, you cannot ignore the individual differences.

This general principle may also account for the lack of effect among younger adults. It is interesting to speculate whether physical activity effects would be found if the younger adults were given much more challenging tasks (either by increasing their difficulty, or selecting a group who were less capable).

Step Rate was calculated by total steps taken divided by the total minutes in light, moderate, and vigorous activities, based on the notion that this would provide an independent indicator of physical activity intensity (how briskly one is walking). Sedentary Time was the total minutes spent sedentary.

http://www.eurekalert.org/pub_releases/2015-11/bumc-slp112415.php

Reference: 

[4045] Hayes SM, Alosco ML, Hayes JP, Cadden M, Peterson KM, Allsup K, Forman DE, Sperling RA, Verfaellie M. Physical Activity Is Positively Associated with Episodic Memory in Aging. Journal of the International Neuropsychological Society [Internet]. 2015 ;21(Special Issue 10):780 - 790. Available from: http://journals.cambridge.org/article_S1355617715000910

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Brain connectivity changes with working memory after TBI

  • A brain imaging study reveals how working memory is impaired after traumatic brain injury.

Brain imaging while 11 individuals with traumatic brain injury and 15 healthy controls performed a working memory task has revealed that those with TBI showed greater connectivity between the hemispheres in the fronto-parietal regions (involved in working memory) and less organized flow of information from posterior to anterior parts.

The study used a new task, known as CapMan, which allows working memory capacity and the mental manipulation of information in working memory to be distinguished from each other.

The discovery may help in the development of more effective therapies.

http://www.eurekalert.org/pub_releases/2015-10/kf-njs102015.php

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Implementation plans help those with low working memory capacity

  • Implementation plans are a strategy for helping you remember your intended future actions.
  • College students with low WMC performed a prospective memory task at the same level as those with a higher WMC, but only when they used a simple implementation plan.

I've written at length about implementation plans in my book “Planning to Remember: How to Remember What You're Doing and What You Plan to Do”. Essentially, they're intentions you make in which you explicitly tie together your intended action with a specific situational cue (such as seeing a post box).

A new study looked at the benefits of using an implementation intention for those with low working memory capacity.

The study involved 100 college students, of whom half were instructed to form an implementation intention in the event-based prospective memory task. The task was in the context of a lexical decision task in which the student had to press a different key depending on whether a word or a pseudo-word was presented, and to press the spacebar when a waiting message appeared between each trial. However (and this is the prospective element), if they saw one of four cue words, they were to stop doing the lexical task and say aloud both the cue word and its associated target word. They were then given the four word pairs to learn.

After they had mastered the word pairs, students in the implementation intention group were also given various sentences to say aloud, of the form: “When I see the word _______ (hotel, eraser, thread, credit) while making a word decision, I will stop doing the lexical decision task and call out _____-______ (hotel-glass, eraser-pencil, thread-book, credit-card) to the experimenter during the waiting message.” They said each sentence (relating to each word pair) twice.

Both groups were given a 5-minute survey to fill out before beginning the trials. At the end of the trials, their working memory was assessed using both the Operation Span task and the Reading Span task.

Overall, as expected, the implementation intention group performed significantly better on the prospective memory task. Unlike other research, there was no significant effect of working memory capacity on prospective memory performance. But this is because other studies haven't used implementation intentions — among those who made no such implement plans, low working memory capacity did indeed negatively affect prospective memory performance. However, those with low working memory capacity did just as well as those with high WMC when they formed implementation intentions (in fact, they did slightly better).

The most probable benefit of the strategy is that it heightened sensitivity to the event cues, something which is of particular value to those with low working memory capacity, who by definition have poorer attentional control.

It should be noted that this was an attentionally demanding task — there is some evidence that working memory ability only relates to prospective memory ability when the prospective memory task requires a high amount of attentional demand. But what constitutes “attentionally demanding” varies depending on the individual.

Perhaps this bears on evidence suggesting that a U-shaped function might apply, with a certain level of cognitive ability needed to benefit from implementation intentions, while those above a certain level find them unnecessary. But again, this depends on how attentionally demanding the task is. We can all benefit from forming implementation intentions in very challenging situations. It should also be remembered that WMC is affected not only more permanently by age, but also more temporarily by stress, anxiety, and distraction.

Of course, this experiment framed the situation in a very short-term way, with the intentions only needing to be remembered for about 15 minutes. A more naturalistic study is needed to confirm the results.

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Unfamiliar accents can make spoken words harder to remember

This is just a preliminary study presented at a recent conference, so we can't give it too much weight, but the finding is consistent with what we know about working memory, and it is of some usefulness.

The study tested the ability of young-adult native English speakers to store spoken words in short-term memory. The English words were spoken either with a standard American accent or with a pronounced but still intelligible Korean accent. Every now and then, the listeners (all unfamiliar with a Korean accent) would be asked to recall the last three words they had heard.

While there was no difference for the last and second-last words, the third word back was remembered significantly better when it was spoken in the familiar accent (80% vs 70%).

The finding suggests that the effort listeners needed to put into understanding the foreign accent used up some of their working memory, reducing their ability to hold onto the information.

The finding is consistent with previous research showing that people with hearing difficulties or who are listening in difficult circumstances (such as over a bad phone line or in a loud room) are poorer at remembering and processing the spoken information compared to individuals who are hearing more clearly.

On a practical level, this finding suggests that, if you're receiving important information (for example, medical information) from someone speaking with an unfamiliar accent, you should make special efforts to remember and process the information. For example, by asking them to speak more slowly, by taking notes and asking for clarification, etc. Those providing such information should take on board the idea that if their listeners are likely to be unfamiliar with their accent, they need to take greater care to speak slowly and clearly, with appropriate levels of repetition and elaboration. Gestures are also helpful for reducing the load on working memory.

http://www.eurekalert.org/pub_releases/2015-05/asoa-htu050715.php

Reference: 

Van Engen, K. et al. 2015. Downstream effects of accented speech on memory. Presentation 1aSC4 at the 169th meeting of the Acoustical Society of America, held May 18-22, 2015 in Pittsburgh, Pennsylvania.

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Why older adults lose working memory capacity

The root of age-related cognitive decline may lie in a reduced ability to ignore distractors. A new study indicates that older adults put more effort into focusing during encoding, in order to compensate for a reduced ability to hold information in working memory. The finding suggests a multi-pronged approach to improving cognitive ability in older adults.

I've reported before on the idea that the drop in working memory capacity commonly seen in old age is related to the equally typical increase in distractability. Studies of brain activity have also indicated that lower WMC is correlated with greater storage of distractor information. So those with higher WMC, it's thought, are better at filtering out distraction and focusing only on the pertinent information. Older adults may show a reduced WMC, therefore, because their ability to ignore distraction and irrelevancies has declined.

Why does that happen?

A new, large-scale study using a smartphone game suggests that the root cause is a change in the way we hold items in working memory.

The study involved 29,631 people aged 18—69, who played a smartphone game in which they had to remember the positions of an increasing number of red circles. Yellow circles, which had to be ignored, could also appear — either at the same time as the red circles, or after them. Data from this game revealed both WMC (how many red circle locations the individual could remember), and distractability (how many red circle locations they could remember in the face of irrelevant yellow circles).

Now this game isn't simply a way of measuring WMC. It enables us to make an interesting distinction based on the timing of the distraction. If the yellow circles appeared at the same time as the red ones, they are providing distraction when you are trying to encode the information. If they appear afterward, the distraction occurs when you are trying to maintain the information in working memory.

Now it would seem commonsensical that distraction at the time of encoding must be the main problem, but the fascinating finding of this study is that it was distraction during the delay (while the information is being maintained in working memory) that was the greater problem. And it was this distraction that became more and more marked with increasing age.

The study is a follow-up to a smaller 2014 study that included two experiments: a lab experiment involving 21 young adults, and data from the same smartphone game involving only the younger cohort (18-29 years; 3247 participants).

This study demonstrated that distraction during encoding and distraction during delay were independent contributory factors to WMC, suggesting that separate mechanisms are involved in filtering out distraction at encoding and maintenance.

Interestingly, analysis of the data from the smartphone game did indicate some correlation between the two in that context. One reason may be that participants in the smartphone game were exposed to higher load trials (the lab study kept WM load constant); another might be that they were in more distracting environments.

While in general researchers have till now assumed that the two processes are not distinct, it has been theorized that distractor filtering at encoding may involve a 'selective gating mechanism', while filtering during WM maintenance may involve a shutting down of perception. The former has been linked to a gating mechanism in the striatum in the basal ganglia, while the latter has been linked to an increase in alpha waves in the frontal cortex, specifically, the left middle frontal gyrus. The dorsolateral prefrontal cortex may also be involved in distractor filtering at encoding.

To return to the more recent study:

  • there was a significant decrease in WMC with increasing age in all conditions (no distraction; encoding distraction; delay distraction)
  • for older adults, the decrease in WMC was greatest in the delay distraction condition
  • when 'distraction cost' was calculated (((ND score − (ED or DD score))/ND score) × 100), there was a significant correlation between delay distraction cost and age, but not between encoding distraction cost and age
  • for older adults, performance in the encoding distraction condition was better predicted by performance in the no distraction condition than it was among the younger groups
  • this correlation was significantly different between the 30-39 age group and the 40-49 age group, between the 40s and the 50s, and between the 50s and the 60s — showing that this is a progressive change
  • older adults with a higher delay distraction cost (ie, those more affected by distractors during delay) also showed a significantly greater correlation between their no-distraction performance and encoding-distraction performance.

All of this suggests that older adults are focusing more attention during attention even when there is no distraction, and they are doing so to compensate for their reduced ability to maintain information in working memory.

This suggests several approaches to improving older adults' ability to cope:

  • use perceptual discrimination training to help improve WMC
  • make working memory training more about learning to ignore certain types of distraction
  • reduce distraction — modify daily tasks to make them more "older adult friendly"
  • (my own speculation) use meditation training to improve frontal alpha rhythms.

You can participate in the game yourself, at http://thegreatbrainexperiment.com/

http://medicalxpress.com/news/2015-05-smartphone-reveals-older.html

Reference: 

[3921] McNab F, Zeidman P, Rutledge RB, Smittenaar P, Brown HR, Adams RA, Dolan RJ. Age-related changes in working memory and the ability to ignore distraction. Proceedings of the National Academy of Sciences [Internet]. 2015 ;112(20):6515 - 6518. Available from: http://www.pnas.org/content/112/20/6515

McNab, F., & Dolan, R. J. (2014). Dissociating distractor-filtering at encoding and during maintenance. Journal of Experimental Psychology. Human Perception and Performance, 40(3), 960–7. doi:10.1037/a0036013

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Clarity in short-term memory shows no link with IQ

December, 2010

The two measures of working memory capacity appear to be fully independent, and only one of them is related to intelligence.

The number of items a person can hold in short-term memory is strongly correlated with their IQ. But short-term memory has been recently found to vary along another dimension as well: some people remember (‘see’) the items in short-term memory more clearly and precisely than other people. This discovery has lead to the hypothesis that both of these factors should be considered when measuring working memory capacity. But do both these aspects correlate with fluid intelligence?

A new study presented 79 students with screen displays fleetingly showing either four or eight items. After a one-second blank screen, one item was returned and the subject asked whether that object had been in a particular location previously. Their ability to detect large and small changes in the items provided an estimate of how many items the individual could hold in working memory, and how clearly they remembered them. These measures were compared with individuals’ performance on standard measures of fluid intelligence.

Analysis of data found that these two measures of working memory — number and clarity —are completely independent of each other, and that it was the number factor only that correlated with intelligence.

This is not to say that clarity is unimportant! Only that it is not related to intelligence.

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