individual differences

Brain flexibility predicts learning speed

June, 2011

New analytic techniques reveal that functional brain networks are more fluid than we thought.

A new perspective on learning comes from a study in which 18 volunteers had to push a series of buttons as fast as possible, developing their skill over three sessions. New analytical techniques were then used to see which regions of the brain were active at the same time. The analysis revealed that those who learned new sequences more quickly in later sessions were those whose brains had displayed more 'flexibility' in the earlier sessions — that is, different areas of the brain linked with different regions at different times.

At this stage, we don’t know how stable an individual’s flexibility is. It may be that individuals vary significantly over the course of time, and if so, this information could be of use in predicting the best time to learn.

But the main point is that the functional modules, the brain networks that are involved in specific tasks, are more fluid than we thought. This finding is in keeping, of course, with the many demonstrations of damage to one region being compensated by new involvement of another region.

Reference: 

[2212] Bassett, D. S., Wymbs N. F., Porter M. A., Mucha P. J., Carlson J. M., & Grafton S. T.
(2011).  Dynamic reconfiguration of human brain networks during learning.
Proceedings of the National Academy of Sciences. 108(18), 7641 - 7646.

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Individual differences in learning motor skills reflect brain chemical

April, 2011

An imaging study demonstrates that people who are quicker at learning a sequence of finger movements have lower levels of the inhibitory chemical GABA.

What makes one person so much better than another in picking up a new motor skill, like playing the piano or driving or typing? Brain imaging research has now revealed that one of the reasons appears to lie in the production of a brain chemical called GABA, which inhibits neurons from responding.

The responsiveness of some brains to a procedure that decreases GABA levels (tDCS) correlated both with greater brain activity in the motor cortex and with faster learning of a sequence of finger movements. Additionally, those with higher GABA concentrations at the beginning tended to have slower reaction times and less brain activation during learning.

It’s simplistic to say that low GABA is good, however! GABA is a vital chemical. Interestingly, though, low GABA has been associated with stress — and of course, stress is associated with faster reaction times and relaxation with slower ones. The point is, we need it in just the right levels, and what’s ‘right’ depends on context. Which brings us back to ‘responsiveness’ — more important than actual level, is the ability of your brain to alter how much GABA it produces, in particular places, at particular times.

However, baseline levels are important, especially where something has gone wrong. GABA levels can change after brain injury, and also may decline with age. The findings support the idea that treatments designed to influence GABA levels might improve learning. Indeed, tDCS is already in use as a tool for motor rehabilitation in stroke patients — now we have an idea why it works.

Reference: 

[2202] Stagg, C J.., Bachtiar V., & Johansen-Berg H.
(2011).  The Role of GABA in Human Motor Learning.
Current Biology. 21(6), 480 - 484.

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Hippocampal volume and PTSD

April, 2011

A new study supports the association between hippocampal size and recovery from PTSD, pointing to the role of neurogenesis in stress resilience.

Following previous research suggesting that the volume of the hippocampus was reduced in some people with chronic PTSD, a twin study indicated that this may not be simply a sign that stress has shrunk the hippocampus, but that those with a smaller hippocampus are at greater risk of PTSD. Now a new study has found that Gulf War veterans who recovered from PTSD had, on average, larger hippocampi than veterans who still suffer from PTSD. Those who recovered had hippocampi of similar size to control subjects who had never had PTSD.

The study involved 244 Gulf War veterans, of whom 82 had lifetime PTSD, 44 had current PTSD, and 38 had current depression.

Because we don’t know hippocampal size prior to trauma, the findings don’t help us decide whether hippocampal size is a cause or an effect (or perhaps it would be truer to say, don’t help us decide the relative importance of these factors, because it seems most plausible that both are significant).

The really important question, of course, is whether an effective approach to PTSD treatment would be to work on increasing hippocampal volume. Exercise and mental stimulation, for example, are known to increase the creation of new brain cells in the hippocampus. In this case, the main mediator is probably the negative effects of stress (which reduces neurogenesis). There is some evidence that antidepressant treatment might increase hippocampal volume in people with PTSD.

The other conclusion we can derive from these findings is that perhaps we should not simply think of building hippocampal volume / creating new brain cells as a means of building cognitive reserve, thus protecting us from cognitive decline and dementia. We should also think of it as a means of improving our emotional resilience and protecting us from the negative effects of stress and trauma.

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Fluency heuristic is not everyone’s rule

April, 2011

Two experiments indicate that judgment about how well something is learned is based on encoding fluency only for people who believe intelligence is a fixed attribute.

It’s well-established that feelings of encoding fluency are positively correlated with judgments of learning, so it’s been generally believed that people primarily use the simple rule, easily learned = easily remembered (ELER), to work out whether they’re likely to remember something (as discussed in the previous news report). However, new findings indicate that the situation is a little more complicated.

In the first experiment, 75 English-speaking students studied 54 Indonesian-English word pairs. Some of these were very easy, with the English words nearly identical to their Indonesian counterpart (e.g, Polisi-Police); others required more effort but had a connection that helped (e.g, Bagasi-Luggage); others were entirely dissimilar (e.g., Pembalut-Bandage).

Participants were allowed to study each pair for as long as they liked, then asked how confident they were about being able to recall the English word when supplied the Indonesian word on an upcoming test. They were tested at the end of their study period, and also asked to fill in a questionnaire which assessed the extent to which they believed that intelligence is fixed or changeable.

It’s long been known that theories of intelligence have important effects on people's motivation to learn. Those who believe each person possesses a fixed level of intelligence (entity theorists) tend to disengage when something is challenging, believing that they’re not up to the challenge. Those who believe that intelligence is malleable (incremental theorists) keep working, believing that more time and effort will yield better results.

The study found that those who believed intelligence is fixed did indeed follow the ELER heuristic, with their judgment of how well an item was learned nicely matching encoding fluency.

However those who saw intelligence as malleable did not follow the rule, but rather seemed to be following the reverse heuristic: that effortful encoding indicates greater engagement in learning, and thus is a sign that they are more likely to remember. This group therefore tended to be marginally underconfident of easy items, marginally overconfident for medium-level items, and significantly overconfident for difficult items.

However, the entanglement of item difficulty and encoding fluency weakens this finding, and accordingly a second experiment separated these two attributes.

In this experiment, 41 students were presented with two lists of nine words, one list of which was in small font (18-point Arial) and one in large font (48-point Arial). Each word was displayed for four seconds. While font size made no difference to their actual levels of recall, entity theorists were much more confident of recalling the large-size words than the small-size ones. The incremental theorists were not, however, affected by font-size.

It is suggested that the failure to find evidence of a ‘non-fluency heuristic’ in this case may be because participants had no control over learning time, therefore were less able to make relative judgments of encoding effort. Nevertheless, the main finding, that people varied in their use of the fluency heuristic depending on their beliefs about intelligence, was clear in both cases.

Reference: 

[2182] Miele, D. B., Finn B., & Molden D. C.
(2011).  Does Easily Learned Mean Easily Remembered?.
Psychological Science. 22(3), 320 - 324.

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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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Women's brains grow after giving birth

November, 2010

A small study indicates that nurturing mothers and increased reward centers in the brain go hand-in-hand — although the jury’s still out on which comes first.

The issue of “mommy brain” is a complex one. Inconsistent research results make it clear that there is no simple answer to the question of whether or not pregnancy and infant care change women’s brains. But a new study adds to the picture.

Brain scans of 19 women two to four weeks and three to four months after they gave birth showed that grey matter volume increased by a small but significant amount in the midbrain (amygdala, substantia nigra, hypothalamus), prefrontal cortex, and parietal lobe. These areas are involved in motivation and reward, emotion regulation, planning, and sensory perception.

Mothers who were most enthusiastic about their babies were significantly more likely to show this increase in the midbrain regions. The authors speculated that the “maternal instinct” might be less of an instinctive response and more of a result of active brain building. Interestingly, while the brain’s reward regions don’t usually change as a result of learning, one experience that does have this effect is that of addiction.

While the reasons may have to do with genes, personality traits, infant behavior, or present circumstances, previous research has found that mothers who had more nurturing in their childhood had more grey matter in those brain regions involved in empathy and reading faces, which also correlated with the degree of activation in those regions when their baby cried.

A larger study is of course needed to confirm these findings.

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Extraverts more vulnerable to effects of sleep deprivation after social interaction

November, 2010

A small study suggests that social activities are more tiring for extraverts than introverts, and that this personality trait may influence the effect of sleep loss on attention.

A study involving 48 healthy adults aged 18-39 has found that extraverts who were deprived of sleep for 22 hours after spending 12 hours in group activities performed worse on a vigilance task that did those extraverts who engaged in the same activities on their own in a private room. Introverts were relatively unaffected by the degree of prior social interaction.

The researchers suggest that social interactions are cognitively complex experiences that may lead to rapid fatigue in brain regions that regulate attention and alertness, and (more radically) that introverts may have higher levels of cortical arousal, giving them greater resistance to sleep deprivation.

Reference: 

Rupp TL; Killgore WDS; Balkin TJ. Socializing by day may affect performance by night: vulnerability to sleep deprivation is differentially mediated by social exposure in extraverts vs introverts. SLEEP 2010;33(11):1475-1485.

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Evidence of the future affecting the present: discussions on what constitutes scientific evidence

Here’s a very cool study: wackily deciding to reverse the normal order of some standard psychology experiments, a researcher has found evidence in eight experiments of future actions or events influencing behavior.

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The precognition paper is available as a preprint at http://www.dbem.ws/FeelingFuture.pdf

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11/2010

Career choice may determine where frontotemporal dementia begins

October, 2010

An international review of patients with frontotemporal dementia has revealed that the area of the brain first affected tends to be the hemisphere least used in the individual’s occupation.

A review of brain imaging and occupation data from 588 patients diagnosed with frontotemporal dementia has found that among the dementias affecting those 65 years and younger, FTD is as common as Alzheimer's disease. The study also found that the side of the brain first attacked (unlike Alzheimer’s, FTD typically begins with tissue loss in one hemisphere) is influenced by the person’s occupation.

Using occupation scores that reflect the type of skills emphasized, they found that patients with professions rated highly for verbal skills, such as school principals, had greater tissue loss on the right side of the brain, whereas those rated low for verbal skills, such as flight engineers, had greater tissue loss on the left side of the brain. This effect was expressed most clearly in the temporal lobes of the brain. In other words, the side of the brain least used in the patient's professional life was apparently the first attacked.

These findings are in keeping with the theory of cognitive reserve, but may be due to some asymmetry in the brain that both inclines them to a particular occupational path and renders the relatively deficient hemisphere more vulnerable in later life.

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Cultural differences & developmental changes in working memory

January, 2010

A comparison of Ugandan and Senegalese children has found differences in which working memory system is dominant. This may be a product of literacy training.

‘Working memory’ is thought to consist of three components: one concerned with auditory-verbal processing, one with visual-spatial processing, and a central executive that controls both. It has been hypothesized that the relationships between the components changes as children develop. Very young children are more reliant on visuospatial processing, but later the auditory-verbal module becomes more dominant. It has also been found that the two sensory modules are not strongly associated in younger (5-8) American children, but are strongly associated in older children (9-12). The same study found that this pattern was also found in Laotian children, but not in children from the Congo, none of whom showed a strong association between visual and auditory working memory. Now a new study has found that Ugandan children showed greater dominance of the auditory-verbal module, particularly among the older children (8 ½ +); however, the visuospatial module was dominant among Senegalese children, both younger and older. It is hypothesized that the cultural differences are a product of literacy training — school enrolment was much less consistent among the Senegalese. But there may also be a link to nutritional status.

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