Is a Bigger Brain Really Better?
Mind-myth 10: Imagine you measure both the bodies and brains of all the primates on Earth bar humans: beasties like bonobos, chimps and gorillas. Then, using this ratio and based on the average human's size, you estimate how big our brains should be.
To check your estimate you decide to open up your friend's head to take a peek inside. When you do, you're mighty surprised to find a brain about three times larger than you were expecting. "Aha," you say, "This is where our amazing capacity for language, emotion, social organisation and creativity comes from."
This argument soon breaks down when you try chatting to an elephant.Naturally, then, it's an attractive idea that the bigger the brain, the more able the animal. This argument soon breaks down, though, when you try chatting to an elephant - an animal with a brain three times the size of ours. OK, you might say, it doesn't work across species, but maybe it works within species.
Well, now trouble is not far away, and here's two reasons why:
- Men's brains are generally bigger than women's, on average by 100 grams (say about 7% bigger).
- Different races have different head sizes with Asian children averaging the largest at birth followed by White children, leaving Black babies with the smallest heads.
So you see the kind of dangerous, shark-infested waters we're now swimming in? This is no longer just science, it's political; with claims to the answer potentially being seen as both sexist and racist.
This is why I'm more than a little relieved to report the view of neuroscientist Dr David P. Carey who has reviewed the research in this area and finds little evidence for the claim that bigger brains mean greater abilities (Carey, 2007). He argues that the evidence from neuroimaging, behavioural genetics and comparative cognition is largely unconvincing:
"I have little confidence that looking at a sophisticated twenty-first century brain scan (in any number of impossibly sophisticated ways) of a collaborator, competitor or any old conspecific [other human] is going to tell me anything meaningful at all about their capabilities to perform in any cognitive way, psychometric or not." (Carey, 2007, p. 119).
Intelligence sceptics
A second layer of scepticism about the brain size/intelligence connection is captured by an old joke that goes like this:
Q: What is intelligence?
A: Whatever intelligence tests measure.
The joke expresses a scepticism many harbour towards measures of intelligence. Does intelligence really tell us anything useful about a person, or does it just tell us how good they are at taking intelligence tests?
The jury is very much out on this point. The originators and manufacturers of intelligence tests will tell you they are good predictors of people's real-world performance, while many others are not so sure. In fact, you'll likely hear equally strong answers from equally well-qualified people that are completely contradictory.
It's not how big it is...
The default position should be a high level of scepticism about any claims for a relationship between brain size and ability. This is because:
- The connection between brain size and intelligence is largely unproven, and;
- The relationship between measures of intelligence and real-world functioning and behaviour is highly contentious.
So, there you have, confirmation of the oldest defence in the book: it's not how big it is, it's what you do with it.
» Find out if any other mind-myths catch you out.
[Image credit: laszlo-photo]
Reference
Carey, D. P. (2007). Is bigger really better? The search for brain size and intelligence in the twenty-first century. In: S. D. Sala (Ed.). Tall tales about the mind and brain: separating fact from fiction. Oxford: Oxford University Press.
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It's not brain size that determines intelligence; it's the brain-body ratio (which is why blue whales aren't taking over the seas). Furthermore, many studies have demonstrated a clear and distinct relationship between head circumference and scores on intelligent tests (Ivanovic et al., 2004). (Yes, I am implying intelligence tests are indicate of intelligence.) Additionally, greater volume of gray matter in the frontal lobe is related to some forms of intelligence (Frangou, Chitins, & Williams, 2004; Haier et al., 2005; Wilke, Sohn, Bryars, and Holland, 2003).
I second reza's point. The argument isn't that brain size alone indicates intelligence, it's the ratio of the brain size to the size of the body.
Reza & Benjamin, if you go by the ratio of brain to body size then mice must be as intelligent as humans (ratio 1:40) while small birds are much more intelligent than humans (1:12).
So this can't be right.
Instead you have to make up a new figure called the 'encephalisation quotient' then take into account body fat and...well...by then it hardly seems worth bothering...
"Instead you have to make up a new figure called the 'encephalisation quotient' then take into account body fat and...well...by then it hardly seems worth bothering..."
If it hardly seems worth bothering then you shouldn't posit that there is no relationship between body vs. brain mass. There has been shown to be a good statistical trend for that as a factor.
I mean, I hate to be a bastard, but you really come off as saying 'why study the physical features of the brain in relation to the body' with that comment.
Hi Doc, this post is about the relationship between ability (intelligence) and brain size. I'm saying there's no proven relationship between those two things in humans - that's the main point.
I agree with you main poimt, but I can note some presumptions (no real science, just a bit of logic):
1. It might be matter not only of size, but also of complexity of its structure.
2. As well, it might be not size of entire brain, but of its specific parts (frontal lobes, for example).
3. And, really, "Whatever intelligence tests measure.". Size might affect, but not imply intelligence (especially anything measurable).
Well, and the other problem with intelligence tests is that not all intelligence is hereditary. Plenty comes from environmental influences.
Jeremy - I think it was just the comments that muddied the waters. The point about brain size in humans and intelligence having little to no relationship is an excellent point.
Does anyone know where I can get my hands on a copy of this Journal article of Careys 2007
James Watson stated that Caucasians have a greater aptitude for intelligence than Africans, also that Asians have a greater aptitude than Caucasians. So this supports the head-size theory. Am I the only one who feels that discoveries should not be covered up because some people might not like to hear the news? It is in the DNA, just pretending the evidence doesn't exist is not going to make it not true. It will, however, hold back out progress. I feel those who demand political correctness in science today, are just as bad as churches were for science hundreds of years ago.
Rebel, it's a chapter in the book: "Tall tales about the mind and brain: separating fact from fiction."
Clearly a contentious issue, from the comments. I thought the article was spot on.
The author posits that there is no correlation between brain size and intelligence. To critique his arguments via other ways of measuring body/brain relationships is not to critique his argument at all.
When he takes up the redirection (ie bait) and puts forward a solution, the readers / comments try to spring the trap, but only catch themselves. Ooof.
I've put enormous research exactly into this issue. Even if one looks only at the brain to body ratio, there is no convincing link. Note, that looking at head size alone is even less relevant since it doesn't give an accurate enough measure of brain size.
Human intelligence results mostly from the structure and organization of the brain (consider the frontal cortex). Even in genetic studies about people with high IQ, there was little correlation with the brain to body ratio. However, there was a high correlation for several clusters of genes. For example, those with a gene resulting in more myelinated axons did better on average. Myelin basically gives better connectivity for the electrical signals of the brain. To sum up, consider processors today. Would you judge how fast a CPU is by its size? If so, the P1 300 Mhz would be dozens of times faster than any single core processor.
I should add an important clarification. The brain size to body ratio is not relevant as long as the brain size is still within the range of normal and if the given size is a natural condition. For example, if one has a smaller brain size due to severe malnutrition or other problems like that, obviously that's going to be a factor.