Are big brains smarter? © iStock

Are big brains smarter?

Larger brain size doesn't always mean you have the highest IQ.

Asked by: Alan Blackwood, by email


To some extent, yes. Across many species the ratio of brain to body weight is a good predictor of intelligence. In fish the ratio is 1:5000, in birds 1:220, in most mammals 1:180 and in humans 1:50.

MRI brain scans reveal a moderate, but consistent correlation between size and IQ among humans of the same sex.  But there are cases of small or damaged brains with high IQs so the rule is not rigid.


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.