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According to many (I cannot find a source at the moment), Albert Einstein's brain weighed less than average.

It is a common belief that there is no correlation between brain mass and intelligence. Is this true?

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"By any measure, Einstein had a smallish brain. Most commentators place it "within the average range," but at 1,230 grams, it weighed almost the same as the brains of Whitman and Gambetta, at the bottom of the list of famous men." NPR: The Long, Strange Journey of Einstein's Brain – Oddthinking♦ Aug 25 '12 at 3:03

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Since Billare already mentioned Michael McDaniel's study I'll point to others.

Canadian researchers found a link between brain size and intelligence:

[they] examined the brains of 100 people who were given extensive IQ tests before they died and found a correlation between cerebral volume and intelligence.

The study looked specifically at the size of the cerebrum, the thinking part of the brain, and found a correlation with verbal intelligence in women. The same correlation was found for right-handed men.


This study found a link between the amount of grey matter and intelligence.

... the amount of gray matter in the frontal lobes turned out to be correlated with intelligence...

but this correlation doesn't necessarily mean causation, as seen in...


... Taxi Drivers' brains "grow" on the job

Cab drivers' grey matter enlarges and adapts to help them store a detailed mental map of the city, according to research.

Taxi drivers given brain scans by scientists at University College London had a larger hippocampus compared with other people.

The scientists also found part of the hippocampus grew larger as the taxi drivers spent more time in the job.


According to this

New research suggests that the layer of insulation coating neural wiring in the brain plays a critical role in determining intelligence.

The neural wires that transmit electrical messages from cell to cell in the brain are coated with a fatty layer called myelin. Much like the insulation on an electrical wire, myelin stops current from leaking out of the wire and boosts the speed with which messages travel through the brain--the higher quality the myelin, the faster the messages travel. These myelin-coated tracts make up the brain's white matter


Here you can read more about the difference between men and women.

Because brain size has been linked with intelligence, it's very tricky to go around saying that men have bigger brains. Yet men do seem to have women beat here; even when accounting for height and weight differences, men have slightly bigger brains. Does this mean they're smarter?

Men also have approximately 6.5 times more gray matter in the brain than women, but before the heads of all the men out there start to swell: Women have about 10 times more white matter than men do.

"These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior," said psychology professor Richard Haier of the University of California.

More sources:

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We have yet to see anyone contribute a definition of "intelligence" here. Difficult to quantify... – M. Werner May 8 '11 at 2:12
@Werner - Yes, that's a problem. It's mentioned in some of the linked articles. – Oliver_C May 8 '11 at 12:23
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No, there is a substantial correlation between brain size and intelligence. The most current citation I know of is a paper from McDaniel 2005, titled: Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence

The abstract reads:

The relationship between brain volume and intelligence has been a topic of a scientific debate since at least the 1830s. To address the debate, a meta-analysis of the relationship between in vivo brain volume and intelligence was conducted. Based on 37 samples across 1530 people, the population correlation was estimated at 0.33. The correlation is higher for females than males. It is also higher for adults than children. For all age and sex groups, it is clear that brain volume is positively correlated with intelligence.

Not all brain regions are equal in contributing to this relationship however; the size of certain tracts, grey-matter tracts in the frontal cortex IIRC (it's been a while since I studied this myself) are the primary determiner of intelligence, as determined by IQ. Allometric scaling probably contributes to this correlation; for example, if a gene unleashes checks on brain growth to enable greater intelligence, it might have a pleiotropic effect on other regions, so that they have to grow bigger as well, though they don't directly contribute to the intelligence of the person whose brain they make up.

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So, by this logic, men are smarter than women, on average? That's what your citation seems to be implying. Also, that elephants are smarter than humans. – Robusto May 7 '11 at 14:12
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You might read through Stephen Jay Gould's The Mismeasure of Man. He goes into great detail on this; it was part of the thinking in Victorian times that brain size had a direct correlation to intelligence, and thus men were more intelligent than women, and of course white European males were the most intelligent of all.... Pretty much shows these notions up as nonsense... Note also that "intelligence" is not quantifiable by simple numbers and is generally regarded as multi-faceted. – M. Werner May 7 '11 at 14:40
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@M. Werner Gould's book is actively regarded as mendacious nonsense by practicing psyshometricians. Unfortunately, it is an enduring mendacity: It is alluring to much of the public who wants science to confirm their prejudices, but as a reviewer wrote of it: "[While] reviews in the popular and literary press...were almost universally effusive in their approbation...most reviews in scientific journals, such as Science (Samelson, 1982), Nature, and Science '82, tended to be critical on a number of counts." Please, do open up a question on Gould. – Billare May 7 '11 at 14:54
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@Billare: A quick glance at the link shows it to be instantly biased, and the author to be quick to throw around insults. That doesn't mean it's wrong, of course, but that's the way I'd bet. – David Thornley May 7 '11 at 18:39
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@Billare In the IQ test you mentioned that resulted in 3-4 points higher for men, note that there were about 10,000 more women than men taking the test, which hightened the chance that men would recieve an overall higher score, so that affected the results heavily. I wouldn't draw up any conclusions from that IQ test therefore, because it wasn't accurate. To add, psychologists regard intelligence as the ability to solve problems and learn/understand complicated material. This would be where math is categorized. In 2003, there was a survey that found eighth-grade girls outperforming boys in alg – user8079 Aug 5 '12 at 18:12
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