July 19, 2004
Brain Gray Matter Size Correlated To Intelligence

Size of grey matter areas of the brain more strongly correlate to IQ than does the overall size of the brain.

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.

Share |      Randall Parker, 2004 July 19 12:23 PM  Brain Intelligence


Comments
nigel said at July 19, 2004 9:31 PM:

So is there any breakdown for geographical ancestry in terms of gray matter distribution? The brain size correlation here is firmly established.

fdsgdfg said at July 20, 2004 5:44 AM:

how long wil it take before it get politcal and culture sigfnicens

Peep Mall said at July 20, 2004 8:45 AM:

I didnt quite get, if the the proportion or size of the grey area, always constant or does it change. In other words, if one learns and solves more and more problems will the grey area grow or does one IQ test define your mental capacity for the rest of your life?

Brock said at July 20, 2004 10:01 AM:

Peep - as I understand it, your understanding of a situation is partly based on connections between brain cells. These connections form all the time as you make new memories and skills. As you 'practice, practice, practice' whatever it is you're doing, you form longer-lasting new connections. You're effectively much better at that task. That being said, if you have 5% more brain cells in the region of the brain that handles that task than the guy next to you, you can form a lot more connections that he will. You'll effectively always have more insight into the task, assuming equal levels of practice and effort and speed of forming new connections.

On the topic of this post though, it's interesting that we're finally getting an idea of what IQ is measuring. My question is, what are the low-IQ people better at? Assuming constant brain volume, Larry-IQ80 has the same number of brain cells as Harry-IQ120. If Larry's brain cells aren't contributing to IQ, what are they contributing to? Does Low-Larry have better visual perception or hand-eye coordination than High-Harry? Maybe Low-Larry has better social-observation hardware which allows him to notice cues which socially oblivious High-Harry never sees. I'll be interested in see how this plays out.

Brock said at July 20, 2004 10:30 AM:

New thought.

At some point we're going to be able to take a 5 year old and stick his head under a scanner and say "Kid, this is what you're good at, and this is what you're not so good at, and this is what you stink at." We'll also have the power to augment certain learning abilities beyond human-normal. We as a society will have to decide, should we concentrate on what he's good at (making him a superb muscician or painter or whatever), or do we concentrate on what he's NOT good at, making him a well-rounded person.

Theoretically, a democracy requires a well-informed citizenry. If we become overly specialized in our disciplines, we can't contribute to 90% of the political discussions of the day. On the other hand, specialization is the key to productivity and economic growth. Where do we make the balance of tradeoffs?

This is already becoming a problem. Take for example the millions of people in Europe who have forgotten how to defend themselves from violence because the U.S.A. is TOO GOOD at defending them with its specialized military. If we become a civilization of extremes, will the "I'm a better mathmatician than Einstein" society even be able to have a conversation with the "We're just like Mozart" folks?

I also think that some countries (*cough* China *cough*) will try to fine-tune the workforce available to them by messing with brains in development. Need for engineers? Just breed 'em up and de-empahsize the competing brain regions, like music appreciation or hand-eye coordination. We'll just breed up a batch of soldiers too, while we're at it. This could lead to a overly-specialized ant-like colony which would probably react violently to global situations it isn't well adapted for.

One more reason for political reform and freedom of evolution in China.

Personally, I think I'd rather live in a socity of Renassaince men than a specialized ant-colony.

Fly said at July 20, 2004 10:19 PM:

Peep Mall : “if one learns and solves more and more problems will the grey area grow or does one IQ test define your mental capacity for the rest of your life?”

Good question. I know some brain areas show considerable plasticity. Training a finger causes the brain region associated with that finger to increase. (Either the brain region grows or old brain areas are retrained.) I know the Hippocampal region is smaller in depressed women and anti-depressants increase neuron growth in that region.

There is also evidence that using the brain either mentally or through regular physical exercise helps retain mental ability. So IQ does respond in a limited fashion to use.

I’d be very interested in seeing what neurotrophic growth factors targeted to those areas would do.

(It is possible that a separate factor causes both higher IQ and the increase in size of those regions. High IQ might have even caused those regions to enlarge.)

Brock: “My question is, what are the low-IQ people better at?”

Picking up women?

It will be interesting to see what further studies show. What regions are larger for superb atheletes?

“We as a society will have to decide, should we concentrate on what he's good at (making him a superb muscician or painter or whatever), or do we concentrate on what he's NOT good at, making him a well-rounded person.”

I believe society will decide to “cure” certain criminal tendencies. (The repeat rate for child molesters is very high. With a highly accurate test and a non-damaging cure I believe society would give the option of lifetime incarceration or cure.) Perhaps there will a list of recommended enhancements, a list of acceptable enhancements, and a black market list of socially unacceptable changes.

I could see China optimizing their citizens. In America I hope we will largely choose for our children and ourselves.

Marilyn vos Savant said at October 31, 2004 10:40 PM:

Hey! I never knew that I had so much grey matter on the front part of my brain! Carpe Diem.

FRANCES SEWELL said at October 29, 2005 3:48 PM:

I HAD A BRAIN SCAN AND IT SHOWED THE WHITE AND GRAY CELLS HAD TINY WHITE SPOTS. I WAS TOLD THE GRAY WAS A SIGN OF LACK OF OXYGEN AND CHANCE OF A STROKE. AND THE WHITE WAS CONFUSION ON COLORS AND ADDING NUMBERS...SUCH AS SOMEONE HOLDS UP THREE FINGERS AND I SAY IT IS TWO. AND MY MIND CAN NOT BE CHANGED...I HOPE I EXPLAINED THIS CORRECTLY. THANK YOU FOR YOUR TIME AND PATIENCE

Domino Harvey said at July 31, 2008 10:13 PM:

I understand that in scientific studies, variables must be controlled, and therefore people are often separated by sex; however, I find it overly simplistic to reduce everything to chromosomal sex. In addition, the article says "These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior,” Richard Haier, professor of psychology in the Department of Pediatrics. But directly above this quote it states "that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance." Therefore are there infinite brain structures capable of same or similar intelligence (which is my gut instinct only) or are we reducing it to gender, that there is the female version and the male version to create equal intelligence (based upon white matter and gray matter)? I hope this makes sense.

Liviana said at November 3, 2008 9:11 PM:

I agree, but it still strange why females at my school scored highest in my math class... But no always I was outstanding In English, Science, Geography, and History, but decent in math, but could never memorize my studies unless I was constantly n task in math.

I had much longer childhood tan most children and developed at a slower pace, i'm at my peak of learning even into my 20s.

My Grandfather was a rarity and could accomplish all subjects beyond what is normal. Fascinating!I agree, but it still strange why females at my school scored highest in my math class... But no always I was outstanding In English, Science, Geography, and History, but decent in math, but could never memorize my studies unless I was constantly n task in math.

I had much longer childhood tan most children and developed at a slower pace, i'm at my peak of learning even into my 20s.

Liviana said at November 3, 2008 9:12 PM:

I agree, but it still strange why females at my school scored highest in my math class... But no always I was outstanding In English, Science, Geography, and History, but decent in math, but could never memorize my studies unless I was constantly n task in math.

I had much longer childhood tan most children and developed at a slower pace, i'm at my peak of learning even into my 20s.

My Grandfather was a rarity and could accomplish all subjects beyond what is normal. Fascinating!
666 My code O_O

matt said at February 24, 2011 9:46 AM:

If only 6 percent of grey matter contributes to IQ then, wouldn't we expect women to be more adept in math and science?

Post a comment
Comments:
Name (not anon or anonymous):
Email Address:
URL:
Remember info?

                       
Go Read More Posts On FuturePundit
Site Traffic Info
The contents of this site are copyright ©