working memory

Working memory has more layers than thought

April, 2011

A new study provides further support for a three-tier model of working memory, where the core only holds one item, the next layer holds up to three, and further items can be passively held ready.

Readers of my books and articles will know that working memory is something I get quite excited about. It’s hard to understate the importance of working memory in our lives. Now a new study tells us that working memory is in fact made up of three areas: a core focusing on one active item, a surrounding area holding at least three more active items (called the outer store), and a wider region containing passive items that have been tagged for later retrieval. Moreover, the core region (the “focus of attention”) has three roles (one more than thought) — it not only directs attention to an item and retrieves it, but it also updates it later, if required.

In two experiments, 49 participants were presented with up to four types of colored shapes on a computer screen, with particular types (eg a red square) confined to a particular column. Each colored shape was displayed in sequence at the beginning with a number from 1 to 4, and then instances of the shapes appeared sequentially one by one. The participants’ task was to keep a count of each shape. Different sequences involved only one shape, or two, three, or four shapes. Participants controlled how quickly the shapes appeared.

Unsurprisingly, participants were slower and less accurate as the set size (number of shape types) increased. There was a significant jump in response time when the set-size increased from one to two, and a steady increase in RT and decline in accuracy as set-size increased from 2 to 4. Responses were also notably slower when the stimulus changed and they had to change their focus from one type of shape to another (this is called the switch cost). Moreover, this switch cost increased linearly with set-size, at a rate of about 240ms/item.

Without getting into all the ins and outs of this experiment and the ones leading up to it, what the findings all point to is a picture of working memory in which:

  • the focus contains only one item,
  • the area outside the focus contains up to three items,
  • this outer store has to be searched before the item can be retrieved,
  • more recent items in the outer store are not found any more quickly than older items in the outer store,
  • focus-switch costs increase as a direct function of the number of items in the outer store,
  • there is (as earlier theorized) a third level of working memory, containing passive items, that is quite separate from the two areas of active storage,
  • that the number of passive items does not influence either response time or accuracy for recalling active items.

It is still unclear whether the passive third layer is really a part of working memory, or part of long-term memory.

The findings do point to the need to use active loads rather than passive ones, when conducting experiments that manipulate cognitive load (for example, requiring subjects to frequently update items in working memory, rather than simply hold some items in memory while carrying out another task).

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Gestures provide a helping hand in problem solving

March, 2011

Another study confirms the value of gestures in helping you solve spatial problems, and suggests that gesturing can help you develop better mental visualization.

In the first of three experiments, 132 students were found to gesture more often when they had difficulties solving mental rotation problems. In the second experiment, 22 students were encouraged to gesture, while 22 were given no such encouragement, and a further 22 were told to sit on their hands to prevent gesturing. Those encouraged to gesture solved more mental rotation problems.

Interestingly, the amount of gesturing decreased with experience with these spatial problems, and when the gesture group were given new spatial visualization problems in which gesturing was prohibited, their performance was still better than that of the other participants. This suggests that the spatial computation supported by gestures becomes internalized. The third experiment increased the range of spatial visualization problems helped by gesture.

The researchers suggest that hand gestures may improve spatial visualization by helping a person keep track of an object in the mind as it is rotated to a new position, and by providing additional feedback and visual cues by simulating how an object would move if the hand were holding it.

Reference: 

[2140] Chu, M., & Kita S.
(2011).  The nature of gestures' beneficial role in spatial problem solving..
Journal of Experimental Psychology: General. 140(1), 102 - 116.

Full text of the article is available at http://www.apa.org/pubs/journals/releases/xge-140-1-102.pdf

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Brief diversions vastly improve focus

March, 2011

A new study suggests we lose focus because of habituation, and we can ‘reset’ our attention by briefly switching to another task before returning.

We’ve all experienced the fading of our ability to concentrate when we’ve been focused on a task for too long. The dominant theory of why this should be so has been around for half a century, and describes attention as a limited resource that gets ‘used up’. Well, attention is assuredly a limited resource in the sense that you only have so much of it to apply. But is it limited in the sense of being used up and needing to refresh? A new study indicates that it isn’t.

The researchers make what strikes me as a cogent argument: attention is an endless resource; we are always paying attention to something. The problem is our ability to maintain attention on a single task without respite. Articulated like this, we are immediately struck by the parallel with perception. Any smell, touch, sight, sound, that remains constant eventually stops registering with us. We become habituated to it. Is that what’s happening with attention? Is it a form of habituation?

In an experimental study, 84 volunteers were tested on their ability to focus on a repetitive computerized task for 50 minutes under various conditions: one group had no breaks or distractions; two groups memorized four digits beforehand and were told to respond if they saw them on the screen during the task (but only one group were shown them during the task); one group were shown the digits but told to ignore them if they saw them.

As expected, performance declined significantly over the course of the task for most participants — with the exception of those who were twice shown the memorized digits and had to respond to them. That was all it took, a very brief break in the task, and their focus was maintained.

The finding suggests that prolonged attention to a single task actually hinders performance, but briefly deactivating and reactivating your goals is all you need to stay focused.

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A positive mood allows your brain to think more creatively

February, 2011

Students who watched a video of a laughing baby or listened to a peppy Mozart piece performed better on a classification task.

A link between positive mood and creativity is supported by a study in which 87 students were put into different moods (using music and video clips) and then given a category learning task to do (classifying sets of pictures with visually complex patterns). There were two category tasks: one involved classification on the basis of a rule that could be verbalized; the other was based on a multi-dimensional pattern that could not easily be verbalized.

Happy volunteers were significantly better at learning the rule to classify the patterns than sad or neutral volunteers. There was no difference between those in a neutral mood and those in a negative mood.

It had been theorized that positive mood might only affect processes that require hypothesis testing and rule selection. The mechanism by which this might occur is through increased dopamine levels in the frontal cortex. Interestingly, however, although there was no difference in performance as a function of mood, analysis based on how closely the subjects’ responses matched an optimal strategy for the task found that, again, positive mood was of significant benefit.

The researchers suggest that this effect of positive mood may be the reason behind people liking to watch funny videos at work — they’re trying to enhance their performance by putting themselves in a good mood.

The music and video clips were rated for their mood-inducing effects. Mozart’s “Eine Kleine Nachtmusik—Allegro” was the highest rated music clip (at an average rating of 6.57 on a 7-point scale), Vivaldi’s Spring was next at 6.14. The most positive video was that of a laughing baby (6.57 again), with Whose Line is it Anyway sound effects scoring close behind (6.43).

Reference: 

[2054] Nadler, R. T., Rabi R., & Minda J P.
(2010).  Better Mood and Better Performance.
Psychological Science. 21(12), 1770 - 1776.

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Computer-based program may help ADHD symptoms in children

January, 2011

A five-week training program to improve working memory has significantly improved working memory, attention, and organization in many children and adolescents with ADHD.

A working memory training program developed to help children with ADHD has been tested by 52 students, aged 7 to 17. Between a quarter and a third of the children showed significant improvement in inattention, overall number of ADHD symptoms, initiation, planning/organization, and working memory, according to parental ratings. While teacher ratings were positive, they did not quite reach significance. It is worth noting that this improvement was maintained at the four-month follow-up.

The children used the software in their homes, under the supervision of their parents and the researchers. The program includes a set of 25 exercises in a computer-game format that students had to complete within 5 to 6 weeks. For example, in one exercise a robot will speak numbers in a certain order, and the student has to click on the numbers the robot spoke, on the computer screen, in the opposite order. Each session is 30 to 40 minutes long, and the exercises become progressively harder as the students improve.

The software was developed by a Swedish company called Cogmed in conjunction with the Karolinska Institute. Earlier studies in Sweden have been promising, but this is the first study in the United States, and the first to include children on medication (60% of the participants).

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Easy Solution for Test Anxiety

January, 2011

New research has come up with a very easy remedy for those who sabotage themselves in exams by being over-anxious — spend a little time writing out your worries just before the test.

It’s well known that being too anxious about an exam can make you perform worse, and studies indicate that part of the reason for this is that your limited working memory is being clogged up with thoughts related to this anxiety. However for those who suffer from test anxiety, it’s not so easy to simply ‘relax’ and clear their heads. But now a new study has found that simply spending 10 minutes before the exam writing about your thoughts and feelings can free up brainpower previously occupied by testing worries.

In the first laboratory experiments, 20 college students were given two math tests. After the first test, the students were told that there would be a monetary reward for high marks — from both them and the student they had been paired with. They were then told that the other student had already sat the second test and improved their score, increasing the pressure. They were also they’d be videotaped, and their performance analyzed by teachers and students. Having thus upped the stakes considerably, half the students were given 10 minutes to write down any concerns they had about the test, while the other half were just given 10 minutes to sit quietly.

Under this pressure, the students who sat quietly did 12% worse on the second test. However those who wrote about their fears improved by 5%. In a subsequent experiment, those who wrote about an unrelated unemotional event did as badly as the control students (a drop of 7% this time, vs a 4% gain for the expressive writing group). In other words, it’s not enough to simply write, you need to be expressing your worries.

Moving out of the laboratory, the researchers then replayed their experiment in a 9th-grade classroom, in two studies involving 51 and 55 students sitting a biology exam. The students were scored for test anxiety six weeks before the exam. The control students were told to write about a topic that wouldn’t be covered in the exam (this being a common topic in one’s thoughts prior to an exam). It was found that those who scored high in test anxiety performed poorly in the control condition, but at the level of those low in test anxiety when in the expressive writing condition (improving their own performance by nearly a grade point). Those who were low in test anxiety performed at the same level regardless of what they wrote about prior to the exam.

One of the researchers, Sian Beilock, recently published a book on these matters: Choke: What the Secrets of the Brain Reveal About Getting It Right When You Have To

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Cognitive recovery after brain damage more complex than realized

January, 2011

Two new studies show us that recovery after brain damage is not as simple as one region ‘taking over’ for another, and that some regions are more easily helped than others.

When stroke or brain injury damages a part of the brain controlling movement or sensation or language, other parts of the brain can learn to compensate for this damage. It’s been thought that this is a case of one region taking over the lost function. Two new studies show us the story is not so simple, and help us understand the limits of this plasticity.

In the first study, six stroke patients who have lost partial function in their prefrontal cortex, and six controls, were briefly shown a series of pictures to test the ability to remember images for a brief time (visual working memory) while electrodes recorded their EEGs. When the images were shown to the eye connected to the damaged hemisphere, the intact prefrontal cortex (that is, the one not in the hemisphere directly receiving that visual input) responded within 300 to 600 milliseconds.

Visual working memory involves a network of brain regions, of which the prefrontal cortex is one important element, and the basal ganglia, deep within the brain, are another. In the second study, the researchers extended the experiment to patients with damage not only to the prefrontal cortex, but also to the basal ganglia. Those with basal ganglia damage had problems with visual working memory no matter which part of the visual field was shown the image.

In other words, basal ganglia lesions caused a more broad network deficit, while prefrontal cortex lesions resulted in a more limited, and recoverable, deficit. The findings help us understand the different roles these brain regions play in attention, and emphasize how memory and attention are held in networks. They also show us that the plasticity compensating for brain damage is more dynamic and flexible than we realized, with intact regions stepping in on a case by case basis, very quickly, but only when the usual region fails.

Reference: 

[2034] Voytek, B., Davis M., Yago E., Barcel F., Vogel E. K., & Knight R. T.
(2010).  Dynamic Neuroplasticity after Human Prefrontal Cortex Damage.
Neuron. 68(3), 401 - 408.

[2033] Voytek, B., & Knight R. T.
(2010).  Prefrontal cortex and basal ganglia contributions to visual working memory.
Proceedings of the National Academy of Sciences. 107(42), 18167 - 18172.

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Distinguishing between working memory and long-term memory

November, 2010

A study with four brain-damaged people challenges the idea that the hippocampus is the hub of spatial and relational processing for short-term as well as long-term memory.

Because people with damage to their hippocampus are sometimes impaired at remembering spatial information even over extremely short periods of time, it has been thought that the hippocampus is crucial for spatial information irrespective of whether the task is a working memory or a long-term memory task. This is in contrast to other types of information. In general, the hippocampus (and related structures in the mediotemporal lobe) is assumed to be involved in long-term memory, not working memory.

However, a new study involving four patients with damage to their mediotemporal lobes, has found that they were perfectly capable of remembering for one second the relative positions of three or fewer objects on a table — but incapable of remembering more. That is, as soon as the limits of working memory were reached, their performance collapsed. It appears, therefore, that there is, indeed, a fundamental distinction between working memory and long-term memory across the board, including the area of spatial information and spatial-objection relations.

The findings also underscore how little working memory is really capable of on its own (although absolutely vital for what it does!) — in real life, long-term memory and working memory work in tandem.

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Sharpening your brain through talking

November, 2010

Indications that talking provides mental stimulation that helps sharpen your brain are supported and explained by new evidence that particular types of conversation are beneficial.

Following on from earlier research suggesting that simply talking helps keep your mind sharp at all ages, a new study involving 192 undergraduates indicates that the type of talking makes a difference. Engaging in brief (10 minute) conversations in which participants were simply instructed to get to know another person resulted in boosts to their executive function (the processes involved in working memory, planning, decision-making, and so on). However when participants engaged in conversations that had a competitive edge, their performance showed no improvement. The improvement was limited to executive function; neither processing speed nor general knowledge was affected.

Further experiments indicated that competitive discussion could boost executive function — if the conversations were structured to allow for interpersonal engagement. The crucial factor seems to be the process of getting into another person’s mind and trying to see things from their point of view (something most of us do naturally in conversation).

The findings also provide support for the social brain hypothesis — that we evolved our larger brains to help us deal with large social groups. They also support earlier speculations by the researcher, that parents and teachers could help children improve their intellectual skills by encouraging them to develop their social skills.

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Insulin sensitivity may explain link between obesity, memory problems

November, 2010

A new study suggests that the link between midlife obesity and cognitive impairment and dementia in old age may be explained by poorer insulin sensitivity.

Previous research has indicated that obesity in middle-age is linked to higher risk of cognitive decline and dementia in old age. Now a study of 32 middle-aged adults (40-60) has revealed that although obese, overweight and normal-weight participants all performed equally well on a difficult cognitive task (a working memory task called the 2-Back task), obese individuals displayed significantly lower activation in the right inferior parietal cortex. They also had lower insulin sensitivity than their normal weight and overweight peers (poor insulin sensitivity may ultimately lead to diabetes). Analysis pointed to the impaired insulin sensitivity mediating the relationship between task-related activation in that region and BMI.

This suggests that it is insulin sensitivity that is responsible for the higher risk of cognitive impairment later in life. The good news is that insulin sensitivity is able to be modified through exercise and diet.

A follow-up study to determine if a 12-week exercise intervention can reverse the differences is planned.

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