intelligence

Education & IQ linked to later cognitive decline & dementia

  • A large, long-running study found those with a college education maintained good cognition substantially longer than those who didn't complete high school.
  • A very large online study found that higher levels of education were strong predictors of better cognitive performance across all ages (15-60 years), but this was more true for types of cognition such as reasoning and less true for processing speed.
  • A large study of older men found that their cognitive ability at age 20 was a stronger predictor of cognitive function later in life than other factors, such as higher education, occupational complexity or engaging in late-life intellectual activities.

Americans with a college education live longer without dementia and Alzheimer's

Data from the large, long-running U.S. Health and Retirement Study found that healthy cognition characterized most of the people with at least a college education into their late 80s, while those who didn’t complete high school had good cognition up until their 70s.

The study found that those who had at least a college education lived a much shorter time with dementia than those with less than a high school education: an average of 10 months for men and 19 months for women, compared to 2.57 years (men) and 4.12 years (women).

The data suggests that those who graduated high school can expect to live (on average) at least 70% of their remaining life after 65 with good cogntion, compared to more than 80% for those with a college education, and less than 50% for those who didn't finish high school.

The analysis was based on a sample of 10,374 older adults (65+; average age 74) in 2000 and 9,995 in 2010.

https://www.eurekalert.org/pub_releases/2018-04/uosc-awa041618.php

https://academic.oup.com/psychsocgerontology/article/73/suppl_1/S20/4971564 (open access)

More education linked to better cognitive functioning later in life

Data from around 196,000 subscribers to Lumosity online brain-training games found that higher levels of education were strong predictors of better cognitive performance across the 15- to 60-year-old age range of their study participants, and appear to boost performance more in areas such as reasoning than in terms of processing speed.

Differences in performance were small for test subjects with a bachelor's degree compared to those with a high school diploma, and moderate for those with doctorates compared to those with only some high school education.

But people from lower educational backgrounds learned novel tasks nearly as well as those from higher ones.

https://www.eurekalert.org/pub_releases/2017-08/l-mel082117.php

http://www.futurity.org/higher-education-cognitive-peak-1523712/

Youthful cognitive ability strongly predicts mental capacity later in life

Data from more than 1,000 men participating in the Vietnam Era Twin Study of Aging revealed that their cognitive ability at age 20 was a stronger predictor of cognitive function later in life than other factors, such as higher education, occupational complexity or engaging in late-life intellectual activities.

All of the men, now in their mid-50s to mid-60s, took the Armed Forces Qualification Test at an average age of 20. The same test of general cognitive ability (GCA) was given in late midlife, plus assessments in seven cognitive domains.

GCA at age 20 accounted for 40% of the variance in the same measure at age 62, and approximately 10% of the variance in each of the seven cognitive domains. Lifetime education, complexity of job and engagement in intellectual activities each accounted for less than 1% of variance at average age 62.

The findings suggest that the impact of education, occupational complexity and engagement in cognitive activities on later life cognitive function simply reflects earlier cognitive ability.

The researchers speculated that the role of education in increasing GCA takes place primarily during childhood and adolescence when there is still substantial brain development.

https://www.eurekalert.org/pub_releases/2019-01/uoc--yca011819.php

Reference: 

[4484] Crimmins, E. M., Saito Y., Kim J. Ki, Zhang Y. S., Sasson I., & Hayward M. D.
(2018).  Educational Differences in the Prevalence of Dementia and Life Expectancy with Dementia: Changes from 2000 to 2010.
The Journals of Gerontology: Series B. 73(suppl_1), S20 - S28.

Guerra-Carrillo, B., Katovich, K., & Bunge, S. A. (2017). Does higher education hone cognitive functioning and learning efficacy? Findings from a large and diverse sample. PLOS ONE, 12(8), e0182276. https://doi.org/10.1371/journal.pone.0182276

[4485] Kremen, W. S., Beck A., Elman J. A., Gustavson D. E., Reynolds C. A., Tu X. M., et al.
(2019).  Influence of young adult cognitive ability and additional education on later-life cognition.
Proceedings of the National Academy of Sciences. 116(6), 2021.

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Movie study confirms older people are more distractible

Idiosyncratic brain activity among older people watching a thriller-type movie adds to evidence that:

  • age may affect the ability to perceive and remember the order of events (explaining why older adults may find it harder to follow complex plots)
  • age affects the ability to focus attention and not be distracted
  • age affects the brain's connectivity — how well connected regions work together.

A study involving 218 participants aged 18-88 has looked at the effects of age on the brain activity of participants viewing an edited version of a 1961 Hitchcock TV episode (given that participants viewed the movie while in a MRI machine, the 25 minute episode was condensed to 8 minutes).

While many studies have looked at how age changes brain function, the stimuli used have typically been quite simple. This thriller-type story provides more complex and naturalistic stimuli.

Younger adults' brains responded to the TV program in a very uniform way, while older adults showed much more idiosyncratic responses. The TV program (“Bang! You're dead”) has previously been shown to induce widespread synchronization of brain responses (such movies are, after all, designed to focus attention on specific people and objects; following along with the director is, in a manner of speaking, how we follow the plot). The synchronization seen here among younger adults may reflect the optimal response, attention focused on the most relevant stimulus. (There is much less synchronization when the stimuli are more everyday.)

The increasing asynchronization with age seen here has previously been linked to poorer comprehension and memory. In this study, there was a correlation between synchronization and measures of attentional control, such as fluid intelligence and reaction time variability. There was no correlation between synchronization and crystallized intelligence.

The greatest differences were seen in the brain regions controlling attention (the superior frontal lobe and the intraparietal sulcus) and language processing (the bilateral middle temporal gyrus and left inferior frontal gyrus).

The researchers accordingly suggested that the reason for the variability in brain patterns seen in older adults lies in their poorer attentional control — specifically, their top-down control (ability to focus) rather than bottom-up attentional capture. Attentional capture has previously been shown to be well preserved in old age.

Of course, it's not necessarily bad that a watcher doesn't rigidly follow the director's manipulation! The older adults may be showing more informed and cunning observation than the younger adults. However, previous studies have found that older adults watching a movie tend to vary more in where they draw an event boundary; those showing most variability in this regard were the least able to remember the sequence of events.

The current findings therefore support the idea that older adults may have increasing difficulty in understanding events — somthing which helps explain why some old people have increasing trouble following complex plots.

The findings also add to growing evidence that age affects functional connectivity (how well the brain works together).

It should be noted, however, that it is possible that there could also be cohort effects going on — that is, effects of education and life experience.

http://www.eurekalert.org/pub_releases/2015-08/uoc-ymt081415.php

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Short online ‘pep talks’ can boost students

A large study shows how a 45-minute online intervention can improve struggling high school students' attitude to schoolwork, and thus their academic performance.

There's been a lot of talk in recent years about the importance of mindset in learning, with those who have a “growth mindset” (ie believe that intelligence can be developed) being more academically successful than those who believe that intelligence is a fixed attribute. A new study shows that a 45-minute online intervention can help struggling high school students.

The study involved 1,594 students in 13 U.S. high schools. They were randomly allocated to one of three intervention groups or the control group. The intervention groups either experienced an online program designed to develop a growth mindset, or an online program designed to foster a sense of purpose, or both programs (2 weeks apart). All interventions were expected to improve academic performance, especially in struggling students.

The interventions had no significant benefits for students who were doing okay, but were of significant benefit for those who had an initial GPA of 2 or less, or had failed at least one core subject (this group contained 519 students; a third of the total participants). For this group, each of the interventions was of similar benefit; interestingly, the combined intervention was less beneficial than either single intervention. It's plausibly suggested that this might be because the different messages weren't integrated, and students may have had some trouble in taking on board two separate messages.

Overall, for this group of students, semester grade point averages improved in core academic courses and the rate at which students performed satisfactorily in core courses increased by 6.4%.

GPA average in core subjects (math, English, science, social studies) was calculated at the end of the semester before the interventions, and at the end of the semester after the interventions. Brief questions before and after the interventions assessed the students' beliefs about intelligence, and their sense of meaningfulness about schoolwork.

GPA before intervention was positively associated with a growth mindset and a sense of purpose, explaining why the interventions had no effect on better students. Only the growth mindset intervention led to a more malleable view of intelligence; only the sense-of-purpose intervention led to a change in perception in the value of mundane academic tasks. Note that the combined intervention showed no such effects, suggesting that it had confused rather than enlightened!

In the growth mindset intervention, students read an article describing the brain’s ability to grow and reorganize itself as a consequence of hard work and good strategies. The message that difficulties don't indicate limited ability but rather provide learning opportunities, was reinforced in two writing exercises. The control group read similar materials, but with a focus on functional localization in the brain rather than its malleability.

In the sense-of-purpose interventions, students were asked to write about how they wished the world could be a better place. They read about the reasons why some students worked hard, such as “to make their families proud”; “to be a good example”; “to make a positive impact on the world”. They were then asked to think about their own goals and how school could help them achieve those objectives. The control group completed one of two modules that didn't differ in impact. In one, students described how their lives were different in high school compared to before. The other was much more similar to the intervention, except that the emphasis was on economic self-interest rather than social contribution.

The findings are interesting in showing that you can help poor learners with a simple intervention, but perhaps even more, for their indication that such interventions are best done in a more holistic and contextual way. A more integrated message would hopefully have been more effective, and surely ongoing reinforcement in the classroom would make an even bigger difference.

http://www.futurity.org/high-school-growth-mindset-910082/

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Birth order has no meaningful effect on personality or IQ

Because this is such a persistent myth, I thought I should briefly report on this massive study that should hopefully put an end to this myth once and for all (I wish! Myths are not so easily squashed.)

This study used data from 377,000 U.S. high school students, and, agreeing with a previous large study, found that first-borns have a one IQ point advantage over later-born siblings, but while statistically significant, this is a difference of no practical significance.

The analysis also found that first-borns tended to be more extroverted, agreeable and conscientious, and had less anxiety than later-borns, — but those differences were “infinitesimally small”, amounting to a correlation of 0.02 (the correlation between birth order and intelligence was .04).

The study controlled for potentially confounding factors, such as a family's economic status, number of children and the relative age of the siblings at the time of the analysis.

A separate analysis of children with exactly two siblings and living with two parents, enabled the finding that there are indeed specific differences between the oldest and a second child, and between second and third children. But the magnitude of the differences was again “minuscule”.

Perhaps it's not fair to say the myth is trounced. Rather, we can say that, yeah, sure, birth order makes a difference — but the difference is so small as not to be meaningful on an individual level.

http://www.eurekalert.org/pub_releases/2015-07/uoia-msb071615.php

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Lower IQ & fitness in teen years increases risk of early-onset dementia

Data from 1.1 million young Swedish men (conscription information taken at age 18) has shown that those with poorer cardiovascular fitness were 2.5 times more likely to develop early-onset dementia later in life and 3.5 times more likely to develop mild cognitive impairment, while those with a lower IQ had a 4 times greater risk of early dementia and a threefold greater risk of MCI. A combination of both poor cardiovascular fitness and low IQ entailed a more than 7 times greater risk of early-onset dementia, and more than 8 times greater risk of MCI.

The increased risk remained even when controlled for other risk factors, such as heredity, medical history, and social-economic circumstances.

The development of early-onset dementia was taken from national disease registries. During the study period, a total of 660 men were diagnosed with early-onset dementia.

A further study of this database, taken from 488,484 men, of whom 487 developed early-onset dementia (at a median age of 54), found nine risk factors for early-onset dementia that together accounted for 68% of the attributable risk. These factors were alcohol intoxication, stroke, use of antipsychotics, depression, father's dementia, drug intoxication other than alcohol, low cognitive function at age 18, low stature at age 18, and high blood pressure at age 18.

http://brain.oxfordjournals.org/content/early/2014/03/06/brain.awu041.abstract

http://www.eurekalert.org/pub_releases/2014-03/uog-lii031014.php

http://www.jwatch.org/content/2013/NA32051?query=etoc_jwneuro

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Intelligence & the brain

See also

Intelligence (research reports)

Older news items (pre-2010) brought over from the old website

Genes more important for IQ as children get older

Data from six studies carried out in the US, the UK, Australia and the Netherlands, involving a total of 11,000 pairs of twins, has revealed that genes become more important for intelligence as we get older. The researchers calculated that genes accounted for some 41% of the variation in intelligence in 9 year olds, rising to 55% in 12 year olds, and 66% in 17 year olds. It was suggested that as they get older, children get better at controlling (or perhaps are allowed to have more control over) their environment, which they do in a way that accentuates their ‘natural’ abilities — bright children feed their abilities; less bright children choose activities and friends that are less challenging.

Haworth, C.M.A. et al. 2009. The heritability of general cognitive ability increases linearly from childhood to young adulthood. Molecular Psychiatry, advance online publication 2 June 2009; doi: 10.1038/mp.2009.55

http://www.newscientist.com/article/mg20327174.600-genes-drive-iq-more-as-kids-get-older.html

A gene that influences intelligence

A study involving more than 2000 people from 200 families has found a link between the gene CHRM2, that activates multiple signaling pathways in the brain involved in learning, memory and other higher brain functions, and performance IQ. Researchers found that several variations within the CHRM2 gene (which is on chromosome 7) could be correlated with slight differences in performance IQ scores, which measure a person's visual-motor coordination, logical and sequential reasoning, spatial perception and abstract problem solving skills, and when people had more than one positive variation in the gene, the improvements in performance IQ were cumulative. Intelligence is a complex attribute that results from a combination of many genetic and environmental factors, so don’t interpret this finding to mean we’ve found a gene for intelligence.

[1173] Edenberg, H., Porjesz B., Begleiter H., Hesselbrock V., Goate A., Bierut L., et al.
(2007).  Association of CHRM2 with IQ: Converging Evidence for a Gene Influencing Intelligence.
Behavior Genetics. 37(2), 265 - 272.

http://www.eurekalert.org/pub_releases/2007-02/wuso-gag022607.php

Common gene version optimizes thinking but carries a risk

On the same subject, another study has found that the most common version of DARPP-32, a gene that shapes and controls a circuit between the striatum and prefrontal cortex, optimizes information filtering by the prefrontal cortex, thus improving working memory capacity and executive control (and thus, intelligence). However, the same version was also more prevalent among people who developed schizophrenia, suggesting that a beneficial gene variant may translate into a disadvantage if the prefrontal cortex is impaired. In other words, one of the things that make humans more intelligent as a species may also make us more vulnerable to schizophrenia.

[864] Kolachana, B., Kleinman J. E., Weinberger D. R., Meyer-Lindenberg A., Straub R. E., Lipska B. K., et al.
(2007).  Genetic evidence implicating DARPP-32 in human frontostriatal structure, function, and cognition.
Journal of Clinical Investigation. 117(3), 672 - 682.

http://www.sciencedaily.com/releases/2007/02/070208230059.htm
http://www.eurekalert.org/pub_releases/2007-02/niom-cgv020707.php

Closing in on the genes involved in human intelligence

A genetic study claims to have identified two regions of the human genome that appear to explain variation in IQ. Previous research has suggested that between 40% and 80% of variation in human intelligence (as measured by IQ tests) can be attributed to genetic factors, but research has so far failed to identify these genes. The new study has identified specific locations on Chromosomes 2 and 6 as being highly influential in determining IQ, using data from 634 sibling pairs. The region on Chromosome 2 that shows significant links to performance IQ overlaps a region associated with autism. The region on Chromosome 6 that showed strong links with both full-scale and verbal IQ marginally overlapped a region implicated in reading disability and dyslexia.

[382] Posthuma, D., Luciano M., Geus E., Wright M., Slagboom P., Montgomery G., et al.
(2005).  A Genomewide Scan for Intelligence Identifies Quantitative Trait Loci on 2q and 6p.
The American Journal of Human Genetics. 77(2), 318 - 326.

Damaged brains show regions involved in intelligence

Comparison of brain scans of 241 patients with differing degrees of cognitive impairment from events such as strokes, tumor resection, and traumatic brain injury, has correlated the location of brain injuries with scores on each of the four indices in the Wechsler Adult Intelligence Scale (WAIS), the most widely used intelligence test in the world. It was found that lesions in the left frontal cortex were associated with lower scores on the verbal comprehension index; lesions in the left frontal and parietal cortex were associated with lower scores on the working memory index; and lesions in the right parietal cortex were associated with lower scores on the perceptual organization index. A surprisingly large amount of overlap in the brain regions responsible for verbal comprehension and working memory may suggest that these two measures of cognitive ability may actually represent the same type of intelligence.

[1179] Gläscher, J., Tranel D., Paul L. K., Rudrauf D., Rorden C., Hornaday A., et al.
(2009).  Lesion Mapping of Cognitive Abilities Linked to Intelligence.
Neuron. 61(5), 681 - 691.

http://www.eurekalert.org/pub_releases/2009-03/ciot-cnm031009.php

When it comes to intelligence, size matters

The NIH MRI Study of Normal Brain Development now contains data from more than 500 children and adolescents from newborns to 18-year-olds, who had brain scans multiple times over a period of years as well as various cognitive tests. A sample of 216 healthy 6 to 18 year old brains from the dataset reveal that there is a positive link between cortical thickness and cognitive ability in many areas of the frontal, parietal, temporal and occipital lobes. The regions with the greatest relationship were the 'multi-modal association' areas, where information converges from various regions of the brain for processing. The finding supports a distributed model of intelligence.

[874] Karama, S., Ad-Dab'bagh Y., Haier R. J., Deary I. J., Lyttelton O. C., Lepage C., et al.
(Submitted).  Positive association between cognitive ability and cortical thickness in a representative US sample of healthy 6 to 18 year-olds.
Intelligence. 37(2), 145 - 155.

http://www.physorg.com/news157210821.html

Processing speed component of intelligence is largely inherited

A new kind of scanner used on the brains of 23 sets of identical twins and 23 sets of fraternal twins has revealed that myelin quality is under strong genetic control in the frontal, parietal, and left occipital lobes, and that myelin quality (in the cingulum, optic radiations, superior fronto-occipital fasciculus, internal capsule, callosal isthmus, and corona radiata) was correlated with intelligence scores. Myelin governs the speed with which signals can travel along the axons of neurons, that is, how fast we can process information. The researchers are now working on finding the genes that may influence myelin growth.

[1310] de Zubicaray, G. I., Wright M. J., Srivastava A., Balov N., Thompson P. M., Chiang M-C., et al.
(2009).  Genetics of Brain Fiber Architecture and Intellectual Performance.
J. Neurosci.. 29(7), 2212 - 2224.

http://www.physorg.com/news156519927.html

Intelligence and rhythmic accuracy go hand in hand

And in another perspective on the nature of intelligence, a new study has demonstrated a correlation between general intelligence and the ability to tap out a simple regular rhythm. The correlation between high intelligence and a good ability to keep time, was also linked to a high volume of white matter in the parts of the frontal lobes involved in problem solving, planning and managing time. The finding suggests that the long-established correlation of general intelligence with the mean and variability of reaction time in elementary cognitive tasks, as well as with performance on temporal judgment and discrimination tasks, is a bottom-up connection, stemming from connectivity in the prefrontal regions.

[665] Ullen, F., Forsman L., Blom O., Karabanov A., & Madison G.
(2008).  Intelligence and Variability in a Simple Timing Task Share Neural Substrates in the Prefrontal White Matter.
J. Neurosci.. 28(16), 4238 - 4243.

http://www.physorg.com/news127561553.html
http://www.eurekalert.org/pub_releases/2008-04/ki-iar041608.php

Brain network related to intelligence identified

A review of 37 imaging studies may have finally answered an age-old question: where is intelligence. Following on from recent evidence suggesting that intelligence is related to how well information travels throughout the brain, the researchers believe they have identified the stations along the routes intelligent information processing takes. These stations primarily involve areas in the frontal and the parietal lobes, many of which are involved in attention and memory, and more complex functions such as language. Basically, the researchers theorize that your level of intelligence is a function of how well these areas communicate with each other. It’s particularly interesting to note that these various imaging studies had remarkably consistent results despite the different definitions of intelligence used in them.

[1015] Jung, R. E., & Haier R. J.
(2007).  The Parieto-Frontal Integration Theory (P-FIT) of Intelligence: Converging Neuroimaging Evidence.
Behavioral and Brain Sciences. 30(02), 135 - 154.

http://www.physorg.com/news108722746.html
http://www.eurekalert.org/pub_releases/2007-09/uoc--bnr091007.php
http://www.livescience.com/health/070911_intel_network.html

Intelligence based on the volume of gray matter in certain brain regions

Confirming earlier suggestions, the most comprehensive structural brain-scan study of intelligence to date supports an association between general intelligence and the volume of gray matter tissue in certain regions of the brain. Because these regions are located throughout the brain, a single "intelligence center" is unlikely. It is likely that a person's mental strengths and weaknesses depend in large part on the individual pattern of gray matter across his or her brain. Although gray matter amounts are vital to intelligence levels, only about 6% of the brain’s gray matter appears related to IQ — intelligence seems related to an efficient use of relatively few structures. The structures that are important for intelligence are the same ones implicated in memory, attention and language. There are also age differences: in middle age, more of the frontal and parietal lobes are related to IQ; less frontal and more temporal areas are related to IQ in the younger adults. Previous research has shown the regional distribution of gray matter in humans is highly heritable. The findings also challenge the recent view that intelligence may be a reflection of more subtle characteristics of the brain, such as the speed at which nerve impulses travel in the brain, or the number of neuronal connections present. It may of course be that all of these are factors.

[715] Haier, R. J., Jung R. E., Yeo R. A., Head K., & Alkire M. T.
(2004).  Structural brain variation and general intelligence.
NeuroImage. 23(1), 425 - 433.

http://www.sciencedaily.com/releases/2004/07/040720090419.htm
http://www.eurekalert.org/pub_releases/2004-07/uoc--hid071904.php

Brain size does matter, but differently for men and women

A study involving the intelligence testing of 100 neurologically normal, terminally ill volunteers, who agreed that their brains be measured after death, found that a bigger brain size is correlated with higher intelligence in certain areas, but there are differences between women and men. Verbal intelligence was clearly correlated with brain size, accounting for 36% of the verbal IQ score, for women and right-handed men — but not for left-handed men. Spatial intelligence was also correlated with brain size in women, but much less strongly, while it was not related at all to brain size in men. It may be that the size or structure of specific brain regions is related to spatial intelligence in men. Brain size decreased with age in men over the age span of 25 to 80 years, suggesting that the well-documented decline in visuospatial intelligence with age is related, at least in right-handed men, to the decrease in cerebral volume with age. However age hardly affected brain size in women.

[1029] Witelson, S. F., Beresh H., & Kigar D. L.
(2006).  Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors.
Brain: A Journal of Neurology. 129(Pt 2), 386 - 398.

http://www.sciencedaily.com/releases/2005/12/051223123116.htm

Correlation between brain volume and intelligence

An analysis of 26 previous international studies involving brain volume and intelligence has found that, on average, intelligence (as measured by standardized intelligence tests) increases with increasing brain volume. The correlation was higher for females than males, and for adults compared to children.

[925] McDaniel, M. A.
(Submitted).  Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence.
Intelligence. 33(4), 337 - 346.

A copy of the study is available at http://www.vcu.edu/uns/Releases/2005/june/McDaniel-Big%20Brain.pdf

http://www.eurekalert.org/pub_releases/2005-06/vcu-vss061705.php
http://www.vcu.edu/uns/Releases/2005/june/061705.html

IQ-related brain areas may differ in men and women

An imaging study of 48 men and women between 18 and 84 years old found that, although men and women performed equally on the IQ tests, the brain structures involved in intelligence appeared distinct. Compared with women, men had more than six times the amount of intelligence-related gray matter, while women had about nine times more white matter involved in intelligence than men did. Women also had a large proportion of their IQ-related brain matter (86% of white and 84% of gray) concentrated in the frontal lobes, while men had 90% of their IQ-related gray matter distributed equally between the frontal lobes and the parietal lobes, and 82% of their IQ-related white matter in the temporal lobes. The implications of all this are not clear, but it is worth noting that the volume of gray matter can increase with learning, and is thus a product of environment as well as genes. The findings also demonstrate that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance.

[938] Haier, R. J., Jung R. E., Yeo R. A., Head K., & Alkire M. T.
(2005).  The neuroanatomy of general intelligence: sex matters.
NeuroImage. 25(1), 320 - 327.

http://www.eurekalert.org/pub_releases/2005-01/uoc--iim012005.php
http://www.sciencedaily.com/releases/2005/01/050121100142.htm

Individual primates display variation in general intelligence

Research into cognition of non-human animals has been concerned almost entirely with the abilities of the species, not with individual variation within a species. Now a study of 22 cotton-top tamarins has revealed that these monkeys, like humans, also display substantial individual variation on tests of broad cognitive ability, although the degree of variation does seem significantly smaller than it is among humans (individual variability accounted for some 20% of the monkey’s performance, while it accounts for some 40-60% of human’s performance on IQ tasks). It may be that greater variability has been an important factor in human brain evolution.

[781] Banerjee, K., Chabris C. F., Johnson V. E., Lee J. J., Tsao F., & Hauser M. D.
(2009).  General Intelligence in Another Primate: Individual Differences across Cognitive Task Performance in a New World Monkey (Saguinus oedipus).
PLoS ONE. 4(6), e5883 - e5883.

Full text available at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005883

http://www.eurekalert.org/pub_releases/2009-06/hu-ipd061209.php

Bigger is smarter: brain size predicts intelligence in different species

Animals with larger body sizes generally have larger brains, and it has generally been assumed that larger animals require larger nervous systems to coordinate their larger bodies. Consequently, comparison of brain size across different animal species, as an indirect measurement of intelligence, have controlled for body size. New research however suggests that, although some correction is probably needed, completely controlling for body size is almost certainly a mistake. Both overall brain size and overall neocortex size proved to be good predictors of intelligence in different primate species.

[998] Deaner, R. O., Isler K., Burkart J., & van Schaik C.
(2007).  Overall Brain Size, and Not Encephalization Quotient, Best Predicts Cognitive Ability across Non-Human Primates.
Brain, Behavior and Evolution. 70(2), 115 - 124.

http://www.sciencedaily.com/releases/2007/05/070518172103.htm

Size of brain areas does matter — but bigger isn't necessarily better

In a fascinating mouse study that overturns our simplistic notion that, when it comes to the brain, bigger is better, researchers have found that there is an optimal size for regions within the brain. The study found that if areas of the cortex involved in body sensations and motor control are either smaller or larger than normal, mice couldn’t run an obstacle course, keep from falling off a rotating rod, or perform other tactile and motor behaviors that require balance and coordination as well as mice with normal-sized areas could. It now seems that the best size in one that is best tuned to the context of the neural system within which that area functions — which is not really so surprising when you consider that every brain region acts as part of a network, in conjunction with other regions. This study builds upon a previous discovery by the same researchers, that a gene controls how the cortex in mice is divided during embryonic development into its functionally specialized areas. Different levels of the protein expressed by this gene changes the size of the sensorimotor areas of the cortex. It is known that significant variability in cortical area size exists in humans, and this may explain at least in part variability in human performance.

[334] Leingärtner, A., Thuret S., Kroll T. T., Chou S-J., Leasure L. J., Gage F. H., et al.
(2007).  Cortical area size dictates performance at modality-specific behaviors.
Proceedings of the National Academy of Sciences. 104(10), 4153 - 4158.

Full text is available at http://tinyurl.com/2tpyhe

http://www.physorg.com/news92051236.html

Bigger brains associated with domain-general intelligence

Analysis of hundreds of studies testing the cognitive abilities of non-human primates provides support for a general intelligence, and confirms that the great apes are more intelligent than monkeys and prosimians. Individual studies have always been criticized for not clearly ensuring that one species wasn’t out-performing another simply because the particular testing situation was more suited to them. However, by looking at so many varied tests, the researchers have overcome this criticism. Although there were a few cases where one species performed better than another one in one task and reversed places in a different task, overall, some species truly outperformed others. The smartest species were clearly the great apes — orangutans, chimpanzees, and gorillas. Moreover, there was no evidence that any species performed especially well within a particular paradigm, contradicting the theory that species differences in intelligence only exist for narrow, specialized skills. Instead, the results argue that some species possess a broad, domain-general type of intelligence that allows them to succeed in a variety of situations.

Deaner, R.O., van Schaik, C.P. & Johnson, V. 2006. Do some taxa have better domain-general cognition than others? A meta-analysis of nonhuman primate studies. Evolutionary Psychology, 4, 149-196.

Full-text available at http://human-nature.com/ep/downloads/ep04149196.pdf

http://www.sciencedaily.com/releases/2006/08/060801231359.htm

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Correlation between emotional intelligence and IQ

February, 2013

A study shows that IQ and conscientiousness significantly predict emotional intelligence, and identifies shared brain areas that underlie this interdependence.

By using brain scans from 152 Vietnam veterans with a variety of combat-related brain injuries, researchers claim to have mapped the neural basis of general intelligence and emotional intelligence.

There was significant overlap between general intelligence and emotional intelligence, both in behavioral measures and brain activity. Higher scores on general intelligence tests and personality reliably predicted higher performance on measures of emotional intelligence, and many of the same brain regions (in the frontal and parietal cortices) were found to be important to both.

More specifically, impairments in emotional intelligence were associated with selective damage to a network containing the extrastriate body area (involved in perceiving the form of other human bodies), the left posterior superior temporal sulcus (helps interpret body movement in terms of intentions), left temporo-parietal junction (helps work out other person’s mental state), and left orbitofrontal cortex (supports emotional empathy). A number of associated major white matter tracts were also part of the network.

Two of the components of general intelligence were strong contributors to emotional intelligence: verbal comprehension/crystallized intelligence, and processing speed. Verbal impairment was unsurprisingly associated with selective damage to the language network, which showed some overlap with the network underlying emotional intelligence. Similarly, damage to the fronto-parietal network linked to deficits in processing speed also overlapped in places with the emotional intelligence network.

Only one of the ‘big five’ personality traits contributed to the prediction of emotional intelligence — conscientiousness. Impairments in conscientiousness were associated with damage to brain regions widely implicated in social information processing, of which two areas (left orbitofrontal cortex and left temporo-parietal junction) were also involved in impaired emotional intelligence, suggesting where these two attributes might be connected (ability to predict and understand another’s emotions).

It’s interesting (and consistent with the growing emphasis on connectivity rather than the more simplistic focus on specific regions) that emotional intelligence was so affected by damage to white matter tracts. The central role of the orbitofrontal cortex is also intriguing – there’s been growing evidence in recent years of the importance of this region in emotional and social processing, and it’s worth noting that it’s in the right place to integrate sensory and bodily sensation information and pass that onto decision-making systems.

All of this is to say that emotional intelligence depends on social information processing and general intelligence. Traditionally, general intelligence has been thought to be distinct from social and emotional intelligence. But humans are fundamentally social animals, and – contra the message of the Enlightenment, that we have taken so much to heart – it has become increasingly clear that emotions and reason are inextricably entwined. It is not, therefore, all that surprising that general and emotional intelligence might be interdependent. It is more surprising that conscientiousness might be rooted in your degree of social empathy.

It’s also worth noting that ‘emotional intelligence’ is not simply a trendy concept – a pop quiz question regarding whether you ‘have a high EQ’ (or not), but that it can, if impaired, produce very real problems in everyday life.

Emotional intelligence was measured by the Mayer, Salovey, Caruso Emotional Intelligence Test (MSCEIT), general IQ by the Wechsler Adult Intelligence Scale, and personality by the Neuroticism-Extroversion-Openness Inventory.

One of the researchers talks about this study on this YouTube video and on this podcast.

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The importance of cognitive control for intelligence

October, 2012

Brain imaging points to the importance of cognitive control, mediated by the connectivity of one particular brain region, for fluid intelligence.

What underlies differences in fluid intelligence? How are smart brains different from those that are merely ‘average’?

Brain imaging studies have pointed to several aspects. One is brain size. Although the history of simplistic comparisons of brain size has been turbulent (you cannot, for example, directly compare brain size without taking into account the size of the body it’s part of), nevertheless, overall brain size does count for something — 6.7% of individual variation in intelligence, it’s estimated. So, something, but not a huge amount.

Activity levels in the prefrontal cortex, research also suggests, account for another 5% of variation in individual intelligence. (Do keep in mind that these figures are not saying that, for example, prefrontal activity explains 5% of intelligence. We are talking about differences between individuals.)

A new study points to a third important factor — one that, indeed, accounts for more than either of these other factors. The strength of the connections from the left prefrontal cortex to other areas is estimated to account for 10% of individual differences in intelligence.

These findings suggest a new perspective on what intelligence is. They suggest that part of intelligence rests on the functioning of the prefrontal cortex and its ability to communicate with the rest of the brain — what researchers are calling ‘global connectivity’. This may reflect cognitive control and, in particular, goal maintenance. The left prefrontal cortex is thought to be involved in (among other things) remembering your goals and any instructions you need for accomplishing those goals.

The study involved 93 adults (average age 23; range 18-40), whose brains were monitored while they were doing nothing and when they were engaged in the cognitively challenging N-back working memory task.

Brain activity patterns revealed three regions within the frontoparietal network that were significantly involved in this task: the left lateral prefrontal cortex, right premotor cortex, and right medial posterior parietal cortex. All three of these regions also showed signs of being global hubs — that is, they were highly connected to other regions across the brain.

Of these, however, only the left lateral prefrontal cortex showed a significant association between its connectivity and individual’s fluid intelligence. This was confirmed by a second independent measure — working memory capacity — which was also correlated with this region’s connectivity, and only this region.

In other words, those with greater connectivity in the left LPFC had greater cognitive control, which is reflected in higher working memory capacity and higher fluid intelligence. There was no correlation between connectivity and crystallized intelligence.

Interestingly, although other global hubs (such as the anterior prefrontal cortex and anterior cingulate cortex) also have strong relationships with intelligence and high levels of global connectivity, they did not show correlations between their levels of connectivity and fluid intelligence. That is, although the activity within these regions may be important for intelligence, their connections to other brain regions are not.

So what’s so important about the connections the LPFC has with the rest of the brain? It appears that, although it connects widely to sensory and motor areas, it is primarily the connections within the frontoparietal control network that are most important — as well as the deactivation of connections with the default network (the network active during rest).

This is not to say that the LPFC is the ‘seat of intelligence’! Research has made it clear that a number of brain regions support intelligence, as do other areas of connectivity. The finding is important because it shows that the left LPFC supports cognitive control and intelligence through a mechanism involving global connectivity and some other as-yet-unknown property. One possibility is that this region is a ‘flexible’ hub — able to shift its connectivity with a number of different brain regions as the task demands.

In other words, what may count is how many different connectivity patterns the left LPFC has in its repertoire, and how good it is at switching to them.

An association between negative connections with the default network and fluid intelligence also adds to evidence for the importance of inhibiting task-irrelevant processing.

All this emphasizes the role of cognitive control in intelligence, and perhaps goes some way to explaining why self-regulation in children is so predictive of later success, apart from the obvious.

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Large drop in IQ in those who smoked marijuana regularly as teens

September, 2012

Persistent marijuana use beginning before age 18 (but not after) is associated with a significant drop in IQ in a large, long-running study.

A large long-running New Zealand study has found that people who started using cannabis in adolescence and continued to use it for years afterward showed a significant decline in IQ from age 13 to 38. This was true even in those who hadn’t smoked marijuana for some years.

The study has followed a group of 1,037 children born in 1972-73. At age 38, 96% of the 1004 living study members participated in the latest assessment. Around 5% were regularly smoking marijuana more than once a week before age 18 (cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 years, and this group was not more or less likely to have dropped out of the study).

This group showed an average decline in IQ of 8 points on cognitive tests at age 38 compared to scores at age 13. Such a decline was not found in those who began using cannabis after the age of 18. In comparison, those who had never used cannabis showed a slight increase in IQ. The effect was dose-dependent, with those diagnosed as cannabis dependent on three or more occasions showing the greatest decline.

While executive function and processing speed appeared to be the most seriously affected areas, impairment was seen across most cognitive domains and did not appear to be statistically significantly different across them.

The size of the effect is shown by a further measure: informants (nominated by participants as knowing them well) also reported significantly more attention and memory problems among those with persistent cannabis dependence. (Note that a decline of 8 IQ points in a group whose mean is 100 brings it down to 92.)

The researchers ruled out recent cannabis use, persistent dependence on other drugs (tobacco, alcohol, hard drugs), and schizophrenia, as alternative explanations for the effect. The effect also remained after years of education were taken into account.

The finding supports the view that the adolescent brain is vulnerable to the effects of marijuana, and that these effects are long-lasting and significant.

Some numbers for those interested: Of the 874 participants included in the analysis (those who had missed at least 3 interviews in the 25 years were excluded), 242 (28%) never used cannabis, 479 (55%) used it but were never diagnosed as cannabis-dependent, and 153 (17%) were diagnosed on at least one of the interviews as cannabis-dependent. Of these, 80 had been so diagnosed on only one occasion, 35 on two occasions, and 38 on three or more occasions. I note that the proportion of males was significantly higher in the cannabis-dependent groups (39% in never used; 49% in used but never diagnosed; 70%, 63%, 82% respectively for the cannabis-dependent).

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Development of mathematics in children — a round-up of recent news

August, 2012
  • Fifth grade students' understanding of fractions and division predicted high school students' knowledge of algebra and overall math achievement.
  • School entrants’ spatial skills predicted later number sense and estimation skills.
  • Gender differences in math performance may rest in part on differences in retrieval practice.
  • ‘Math’ training for infants may be futile, given new findings that they’re unable to integrate two mechanisms for number estimation.

Grasp of fractions and long division predicts later math success

One possible approach to improving mathematics achievement comes from a recent study finding that fifth graders' understanding of fractions and division predicted high school students' knowledge of algebra and overall math achievement, even after statistically controlling for parents' education and income and for the children's own age, gender, I.Q., reading comprehension, working memory, and knowledge of whole number addition, subtraction and multiplication.

The study compared two nationally representative data sets, one from the U.S. and one from the United Kingdom. The U.S. set included 599 children who were tested in 1997 as 10-12 year-olds and again in 2002 as 15-17-year-olds. The set from the U.K. included 3,677 children who were tested in 1980 as 10-year-olds and in 1986 as 16-year-olds.

You can watch a short video of Siegler discussing the study and its implications at http://youtu.be/7YSj0mmjwBM.

Spatial skills improve children’s number sense

More support for the idea that honing spatial skills leads to better mathematical ability comes from a new children’s study.

The study found that first- and second-graders with the strongest spatial skills at the beginning of the school year showed the most improvement in their number line sense over the course of the year. Similarly, in a second experiment, not only were those children with better spatial skills at 5 ½ better on a number-line test at age 6, but this number line knowledge predicted performance on a math estimation task at age 8.

Hasty answers may make boys better at math

A study following 311 children from first to sixth grade has revealed gender differences in their approach to math problems. The study used single-digit addition problems, and focused on the strategy of directly retrieving the answer from long-term memory.

Accurate retrieval in first grade was associated with working memory capacity and intelligence, and predicted a preference for direct retrieval in second grade. However, at later grades the relation reversed, such that preference in one grade predicted accuracy and speed in the next grade.

Unlike girls, boys consistently preferred to use direct retrieval, favoring speed over accuracy. In the first and second grades, this was seen in boys giving more answers in total, and more wrong answers. Girls, on the other hand, were right more often, but responded less often and more slowly. By sixth grade, however, the boys’ practice was paying off, and they were both answering more problems and getting more correct.

In other words, while ability was a factor in early skilled retrieval, the feedback loop of practice and skill leads to practice eventually being more important than ability — and the relative degrees of practice may underlie some of the gender differences in math performance.

The findings also add weight to the view being increasingly expressed, that mistakes are valuable and educational approaches that try to avoid mistakes (e.g., errorless learning) should be dropped.

Infants can’t compare big and small groups

Our brains process large and small numbers of objects using two different mechanisms, seen in the ability to estimate numbers of items at a glance and the ability to visually track small sets of objects. A new study indicates that at age one, infants can’t yet integrate those two processes. Accordingly, while they can choose the larger of two sets of items when both sets are larger or smaller than four, they can’t distinguish between a large (above four) and small (below four) set.

In the study, infants consistently chose two food items over one and eight items over four, but chose randomly when asked to compare two versus four and two versus eight.

The researchers suggest that educational programs that claim to give children an advantage by teaching them arithmetic at an early age are unlikely to be effective for this reason.

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