Evidence is accumulating that brain structure is under considerable genetic influence [Peper et al., 2007]. Puberty, the transitional phase from childhood into adulthood, involves changes in brain morphology that may be essential to optimal adult functioning. Around the onset of puberty gray matter volume starts to decrease, while white matter volume is still increasing [Giedd et al., 1999].
Recent findings have shown, that variation in total gray and white matter volume of the adult human brain is primarily (70–90%) genetically determined [Baare et al, 2001] and in a recent magnetic resonance imaging (MRI) brain study with 45 monozygotic and 61 dizygotic 9-year-old twin-pairs, and their 87 full siblings also high heritabilities have been found [Peper et al, in preparation]. Thus, while environmental influences may play a role in later stages during puberty, around the onset of puberty brain volumes are already highly heritable.
The more genes are found that influence intelligence the greater will be the desire of future parents to use reproductive technologies to make little Jill and Johnnie smarter. Reports like this one indicate that we are coming up on a mad scramble to use offspring genetic engineering technologies. Us older people will be dumb compared to the average child born 50 years from now. If you are smart then are you prepared to find yourself in the left hand side of the intelligence distribution? Or do you plan to use cybernetic implants to keep up with the younger generations?
These researchers compared the volumes of a large number of areas of the brain between twins while also testing them for intelligence. They found genetic influences on the brain density of many areas of the brain as well as genetic influences on intelligence.
Although genetic effects on morphology of specific gray matter areas in the brain have been studied, the heritability of focal white matter was unknown until recently. Similarly, it was unresolved whether there is a common genetic origin of focal gray matter and white matter structures with intelligence. In our study involving 54 monozygotic and 58 dizygotic twin pairs and their 34 singleton siblings, verbal, and performal intelligence were found to share a common genetic origin with an anatomical neural network involving the frontal, occipital, and parahippocampal gray matter and connecting white matter of the superior occipitofrontal fascicle, and the corpus callosum [Hulshoff Pol et al., 2006]. For the genetic analyses, structural equation modeling and voxel-based morphometry were used. To explore the common genetic origin of focal gray matter and white matter areas with intelligence, cross-trait/cross-twin correlations were obtained in which the focal gray matter and white matter densities of each twin are correlated with the psychometric intelligence quotient of his/her cotwin.
The results of this study indicate that genes significantly influence white matter density of the superior occipitofrontal fascicle, corpus callosum, optic radiation, and corticospinal tract, as well as gray matter density of the medial frontal, superior frontal, superior temporal, occipital, postcentral, posterior cingulate, and parahippocampal cortices. Moreover, the results show that intelligence shares a common genetic origin with superior occipitofrontal, callosal, and left optical radiation white matter and frontal, occipital, and parahippocampal gray matter (phenotypic correlations up to 0.35).
These researchers aren't doing DNA sequencing because DNA sequencing still costs too much. But with costs of DNA sequencing and DNA testing rapidly falling brain researchers are going to be able to do massive genetic comparisons in 5 to 10 years that will give them a large enough quantity of genetic information to be able to run down and identify the genetic variations that cause differences in brain density, brain volume, and intelligence. Brain scans on much larger sets of twins combined with full genetic sequencing on those same twins will answer many of the questions we have about genetics and intelligence.
Ever feel like you are at 2 minds about something?
June 19, 2007 -- A probe of the upper echelons of the human brain's chain-of-command has found strong evidence that there are not one but two complementary commanders in charge of the brain, according to neuroscientists at Washington University School of Medicine in St. Louis.
It's as if Captains James T. Kirk and Jean-Luc Picard were both on the bridge and in command of the same starship Enterprise.
In reality, these two captains are networks of brain regions that do not consult each other but still work toward a common purpose — control of voluntary, goal-oriented behavior. This includes a vast range of activities from reading a word to searching for a star to singing a song, but likely does not include involuntary behaviors such as control of the pulse rate or digestion.
Brain scans show two separate networks of nodes making decisions.
Using an analytic technique originally developed by Raichle's group, scientists employed resting state functional connectivity MRI to identify pairs of brain regions where blood oxygen levels rose and fell roughly in synch with each other, implying the regions likely work together. They graphed the results, representing each brain region with a shape. They drew a line between paired brain regions if their blood oxygenation patterns correlated tightly enough. "You might expect that everything is connected to everything, and you would get sort of a big mess and not much information," Dosenbach says. "But that's not at all what we found. Even at low levels of correlation, there were two sides to these graphs. Brain regions on either side had multiple connections to other regions on their side, but they never connected to regions on the opposite side."
The two networks seem to have different purposes. The frontoparietal network sounds like it is more reactive.
Having established that two control networks existed, researchers turned back to their functional brain scans for insight into the networks' roles. One network, dubbed the cinguloopercular network, was linked to a "sustain" signal.
"When you start doing a task, this signal turns on," Petersen explains. "It stays constant while you're doing the task, and then when you're done it turns off."
In contrast, the frontoparietal network was consistently active at the start of mental tasks and during the correction of errors.
The balance between the two networks could vary from individual to individual. For example, some people might be better at maintaining a constant activity and others might be better at reacting to events.
GLEN OAKS, NY -- Psychiatric researchers at The Zucker Hillside Hospital campus of The Feinstein Institute for Medical Research have uncovered evidence of a gene that appears to influence intelligence. Working in conjunction with researchers at Harvard Partners Center for Genetics and Genomics in Boston, the Zucker Hillside team examined the genetic blueprints of individuals with schizophrenia, a neuropsychiatric disorder characterized by cognitive impairment, and compared them with healthy volunteers. They discovered that the dysbindin-1 gene (DTNBP1), which they previously demonstrated to be associated with schizophrenia, may also be linked to general cognitive ability. The study is published in the May 15 print issue of Human Molecular Genetics, available online today, April 27.
"A robust body of evidence suggests that cognitive abilities, particularly intelligence, are significantly influenced by genetic factors. Existing data already suggests that dysbindin may influence cognition," said Katherine Burdick, PhD, the study's primary author. "We looked at several DNA sequence variations within the dysbindin gene and found one of them to be significantly associated with lower general cognitive ability in carriers of the risk variant compared with non-carriers in two independent groups."
The study involved 213 unrelated Caucasian patients with schizophrenia or schizoaffective disorder and 126 unrelated healthy Caucasian volunteers. The researchers measured cognitive performance in all subjects. They then analyzed participants' DNA samples. The researchers specifically examined six DNA sequence variations, also known as single nucleotide polymorphisms (SNPs), in the dysbindin gene and found that one specific pattern of SNPs, known as a haplotype, was associated with general cognitive ability: Cognition was significantly impaired in carriers of the risk variant in both the schizophrenia group and the healthy volunteers as compared with the non-carriers.
"While our data suggests the dysbindin gene influences variation in human cognitive ability and intelligence, it only explained a small proportion of it -- about 3 percent. This supports a model involving multiple genetic and environmental influences on intelligence," said Anil Malhotra, MD, principal investigator of the study.
As DNA sequencing costs fall and larger amounts of genetic sequence differences are collected in humans many more genetic variations that influence intelligence and other cognitive characteristics will be found. The rate at which such genetic variations are identified will go up by orders of magnitude in the next 10 years.
These results are consistent with lots of other studies which found a positive correlation between brain size and intelligence. Bigger is better.
Brain size matters for intellectual ability and bigger is better, McMaster University researchers have found.
The study, led by neuroscientist Sandra Witelson, a professor in the Michael G. DeGroote School of Medicine, and published in the December issue of the journal Brain, has provided some of the clearest evidence on the underlying basis of differences in intelligence.
The study involved testing of intelligence in 100 neurologically normal, terminally ill volunteers, who agreed that their brains be measured after death.
It found bigger is better, but there are differences between women and men.
In women, verbal intelligence was clearly correlated with brain size, accounting for 36 percent of the verbal IQ score. In men, this was true for right-handers only, indicating that brain asymmetry is a factor in men.
Spatial intelligence was also correlated with brain size in women, but less strongly. In men, spatial ability was not related to overall brain size. These results suggest that women may use verbal strategies in spatial thinking, but that in men, verbal and spatial thinking are more distinct.
How hard is it to measure gray versus white matter volumes in dead brains? My guess from other reading is that spatial reasoning abilities will vary more as a function of gray matter volume and perhaps more for gray matter in some areas of the brain than other areas.
It may be that the size or structure of the localized brain regions which underlie spatial skills in men is related to spatial intelligence, as was shown in previous research in Witelson's lab on the brain of Albert Einstein.
In a further sex difference, brain size decreased with age in men over the age span of 25 to 80 years, but age hardly affected brain size in women. It is not known what protective factors, which could be genetic, hormonal or environmental, operate in women.
It remains to be determined what the contribution of nature and nurture are to this cerebral size relationship with intelligence, Witelson said. She added that the results point to the need for responsibility in considering the likely future use of magnetic imaging (or MRIs) of brain structure as a measure of ability in student and workforce settings.
"We're going to need to be careful if, in the future, we use MRI brain scans as a measure of ability in any selection process," she said.
That brain size should correlate with intelligence strikes me as unsurprising on a number of grounds. The brain burns a disproportionate amount of fuel for its size. The brain is expensive for the body. Why should it be bigger unless being bigger provides some Darwinian fitness benefit? For larger brains to offer no benefit the people with smaller brains would need to have mutations that allow them to process just as much information but in a smaller space. But then why wouldn't such mutations sweep through a population?
I'm expecting we'll see the development of far more accurate ways to measure intelligence using MRI and other physical measures.
- One in five will break off from a business or social engagement to respond to a message.
- Nine out of 10 people thought colleagues who answered messages during face-to-face meetings were rude, while three out of 10 believed it was not only acceptable, but a sign of diligence and efficiency.
Note that if 9 out of 10 thinks it is rude to answer messages but 3 out of 10 think it is acceptable then doesn't that suggest that at least 2 out of ten think answering email messages while in meetings is both rude and acceptable? Hmmm....
Better to be stoned than to lose sleep or be interrupted?
- In 80 clinical trials, Dr. Glenn Wilson, a psychiatrist at King's College London University, monitored the IQ of workers throughout the day. He found the IQ of those who tried to juggle messages and work fell by 10 points -- the equivalent to missing a whole night's sleep and more than double the 4-point fall seen after smoking marijuana.
"This is a very real and widespread phenomenon," Wilson said. "We have found that this obsession with looking at messages, if unchecked, will damage a worker's performance by reducing their mental sharpness.
How real is this phenomenon? In my first real job I was placed in a small office next to the company's machine shop. While I tried to debug the software and hardware for a scientific instrument next door I heard drilling and hammering. I went to a gunshop and bought one of those headsets that target practice gunners use to protect their ears. It helped some.
"Companies should encourage a more balanced and appropriate way of working."
But many managers want their workers to promptly answer messages, promptly answer the phone, and come out to meetings and other distractions from getting work done.
Wilson said the IQ drop was even more significant in the men who took part in the tests.
"This is very, very real; but it is not a new phenomenon." Adam Boettiger, an author, publisher and professional coach to executives on time management and managing email overload says. "I've suspected the connection and witnessed it first-hand for years. Why this is a significant find is because (to my knowledge) it is the first clinical study that makes the connection."
Adam Boettiger is right. This is so not new.
Eighty volunteers were asked to carry out problem solving tasks, firstly in a quiet environment and then while being bombarded with new emails and phone calls. Although they were told not to respond to any messages, researchers found that their attention was significantly disturbed.
Alarmingly, the average IQ was reduced by 10 points - double the amount seen in studies involving cannabis users. But not everyone was affected by to the same extent - men were twice as distracted as women.
Some things seem destined for repeat discovery until the results are finally taken seriously. Tom DeMarco and Timothy Lister reported years ago in their book Peopleware that computer programmers who get interrupted often enough by phone calls, intercom announcements, and other sources of interruption get literally nothing done. While the book is a vague memory for me at this point I recall that as part of their consulting work they did studies in companies where they measured the ability of staffs to complete some standard programming assignments and had the staffs keep records of their interruptions. Interrupt rates accounted for a large portion of differences in programmer productivity between companies. Some companies seem intent on treating their programmers and other knowledge workers as highly interruptible and distractable. Go figure.
The extent to which distractions decrease productivity depends on the type of mental work being performed. Some people work on much larger mental tasks, Therefore interrupts cause them to lose a lot of context from working memory. A person who is trying to picture and move around between many parts of a large computer program or a silicon chip design suffers a greater loss in productivty from being interrupted than, for example, a person who handles 5 minute service calls where the answers are pretty rote. Someone who writes complex technical manuals or who tries to find connections between many parts of a complex body of law similarly may hold a lot of mental state and the cost of interruption of such a person is much higher than, say, a person who is simply proofreading a legal document for obvious syntax and grammar errors.
Methods of batchng up interrupts would allow workers to have longer stretches of mental time during which to concentrate on handling large interacting sets of rules and relationships. For example, rather than having all email arrive immediately an email program could be set to check email only at many hour intervals. Perhaps email inboxes should be updated at lunch time so that a person could come back from lunch and process all new morning email at once. Also, imagine phone extensions where the message at the extension reports up "Bob will not be accepting calls for the next 93 minutes. Please call back at 3:30 PM to reach Bob".
Loud intercom announcements are evil, mmmkay? (and before anyone corrects my spelling you should hear that in the voice of Mr. Mackey of South Park) Then we come to cubicle land conditions where every office conversation carries over 5 foot high walls to interrupt the concentration of minds in at least a half dozen other cubicles. What to say about this madness? Words fail me. Working at home is much more productive.
Update: Note the larger effective IQ drop in men than in women. This is consistent observations I've read elsewhere: Women are less irritated by interruptions and can function better through interruptions. Is this a female adaptation for child raising? Young children are like distraction machines. A mother can't get too wrapped up in some work or else her toddlers might wander off into danger. Even if they are nearby they make noises or do other things that demand attention. Are female minds better adapted to dealing with these interrupts?
Men spend less time raising children even after decades of feminist demands for change. Our male ancestors were hunting while the women were gathering. Maybe male pursuits historically had less distractions and required focused concentration that was easier to achieve.
Another point here: Modern technology automates the production of distractions. Will the problem get worse? Think about futuristic movies that show signs reading the identity of passersby and generating voices that speak to each passing person by their real name. Think about advertisements geared ever more precisely to the interests of each customer. Sounds like a recipe for increasing distaction, lower productivity, and unhappier lives.
The technologies which produce distractions appear to be mining fertile ground. Human minds seem drawn to many kinds of distractions. Are we stimulus junkies? Or are our minds wired up to evaluate distractions as potential attacks from predators? Did selective pressure on our neolithic ancestors make our minds geared up to constantly evaluate messages from humans in order to check for potential threats?
But technology also provides means to filter out distractions. Don't want to look through bills every month? Set up auto-pay from your checking account to various utilities and credit cards. Also, tune in to satellite radio stations that have no commercials. Or listen to prerecorded music from your own music database rather than listen to a radio station. Lower tech methods to reduce distractions include soundproofing and closing the blinds. I personally like to work in low lighting conditions so that the clutter around me won't distract my mind from the computer screens in front of me.
Once business executives finally understand that they are providing productivity-robbing work environments to their employees (and business managers appear to be slow learners on this score) we can expect to see lower distraction workplaces become all the rage. Some of the distraction lowering technologies developed for workplaces will find their way into homes as well.
Some day in the future cars will drive themselves for much of commuter trips down electronically instrumented highways. Before then more people will work from home and at least for some home workers the distractions of driving will be eliminated altogether. But we need to find more lower and higher tech ways to reduce the distractions that lower our productivity and reduce our ability to enjoy leisure activities.
General human intelligence appears to be based on the volume of gray matter tissue in certain regions of the brain, UC Irvine College of Medicine researchers have found in the most comprehensive structural brain-scan study of intelligence to date.
The study also discovered that because these regions related to intelligence are located throughout the brain, a single “intelligence center,” such as the frontal lobe, is unlikely.
Dr. Richard Haier, professor of psychology in the Department of Pediatrics and long-time human intelligence researcher, and colleagues at UCI and the University of New Mexico used MRI to obtain structural images of the brain in 47 normal adults who also took standard intelligence quotient tests. The researchers used a technique called voxel-based morphometry to determine gray matter volume throughout the brain which they correlated to IQ scores. Study results appear on the online version of NeuroImage.
Previous research had shown that larger brains are weakly related to higher IQ, but this study is the first to demonstrate that gray matter in specific regions in the brain is more related to IQ than is overall size. Multiple brain areas are related to IQ, the UCI and UNM researchers have found, and various combinations of these areas can similarly account for IQ scores. Therefore, 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.
“This may be why one person is quite good at mathematics and not so good at spelling, and another person, with the same IQ, has the opposite pattern of abilities,” Haier said.
While gray matter amounts are vital to intelligence levels, the researchers were surprised to find that only about 6 percent of all the gray matter in the brain appears related to IQ.
Attempts to deny the significance of IQ tests are being undermined by the results of physical measures of the brain using brain scanning technologies. The fact that IQ test correlates with the size of a particular type of brain tissue is a very strong indicator that IQ tests are measuring real physical differences in brain abilities.
The researchers found a curious result with the size of brain gray matter areas, age, and IQ correlation.
The findings also suggest that the brain areas where gray matter is related to IQ show some differences between young-adult and middle-aged subjects. 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.
The research does not address why some people have more gray matter in some brain areas than other people, although previous research has shown the regional distribution of gray matter in humans is highly heritable. Haier and his colleagues are currently evaluating the MRI data to see if there are gender differences in IQ patterns.
My guess is that the frontal areas are still developing in young adults and so are not capable of fully contributing to measured IQ until later in life. Though this article is too vague to tell what they mean by "young-adult".
Update: A January 2005 update on Haier's work shows that male and female brains differ greatly in their organization.
The study shows women having more white matter and men more gray matter related to intellectual skill, revealing that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance.
“These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior,” said Richard Haier, professor of psychology in the Department of Pediatrics and longtime human intelligence researcher, who led the study with colleagues at UCI and the University of New Mexico. “In addition, by pinpointing these gender-based intelligence areas, the study has the potential to aid research on dementia and other cognitive-impairment diseases in the brain.”
Study results appear on the online version of NeuroImage.
In general, men have approximately 6.5 times the amount of gray matter related to general intelligence than women, and women have nearly 10 times the amount of white matter related to intelligence than men. Gray matter represents information processing centers in the brain, and white matter represents the networking of – or connections between – these processing centers.
This, according to Rex Jung, a UNM neuropsychologist and co-author of the study, may help to explain why men tend to excel in tasks requiring more local processing (like mathematics), while women tend to excel at integrating and assimilating information from distributed gray-matter regions in the brain, such as required for language facility.
The environmentalist Blank Slate view of the mind is becoming ever harder to defend.