The human brain

Is a bigger brain a cleverer brain?

It was once thought that having a bigger brain makes you more clever, but that isn’t true

Women’s brains are, on average, 9 per cent smaller than men’s (and so contain fewer neurons), but women are not less intelligent than men; the size difference just reflects the fact that women’s bodies are generally smaller.

Brain size and intelligence are definitely linked, however, but we still don’t know exactly how. While human brains are large, weighing in at an average of 1.4 kg, they pale in comparison to the brains of elephants (2.8 kg), yet human intellect is still uniquely advanced. What seems to be more important than overall size is which areas of the brain are enlarged and how the neurons are connected to each other.

Studies of Albert Einstein’s brain illustrate just how complicated the relationship between brain size and intelligence is. Einstein is often said to be one of the most intelligent people that ever lived, and researchers naturally believed his brain might provide important clues about what made him so clever. When he died, they were surprised to discover that his brain was actually quite small. It weighed 1.23 kg, or about 200 g lighter than the average of 1.4 kg, and the temporal lobes – which contain areas that are specialised for speech and language – were also smaller than average. 

Scientists who examined Einstein’s brain also claim to have found some unusual differences that help to explain why he was so intelligent. For example, his parietal lobes, which are important for mathematical abilities and visual and spatial functions, were about 15 per cent wider than average. They also had an unusual pattern of grooves and ridges, and certain regions of the parietal lobes had more glial cells per neuron than normal.

However, many researchers disagree with these claims; they point to the fact that the original studies tested seven different measures in four brain areas, and only one (number of glial cells per neuron) produced a significant result. In context, they state that this may not mean there’s anything special about Einstein’s brain, as statistically, one out of 28 studies might be expected to produce a result by chance. In terms of size and shape, they argue that it is bad science to look at one individual and state that they are abnormal simply because they deviate from the population average. In reality, the differences noted in his brain are likely to be within the normal and expected range.

This debate highlights many issues that scientists need to be aware of, for example the problem of confirmation bias’the phenomenon where a person has a pre-existing belief or theory, and then views anything they see as confirming that view. In this context, such a belief might be: ‘Einstein was very intelligent, and there must be structural differences in his brain that underlie this intelligence.’ Therefore, when something does appear different from the average, it is assumed that this is a cause of intelligence, rather than it being simply down to chance.

The debate over Einstein’s brain demonstrates how complex researching the brain is, how little we know about how the physical brain structure produces intelligence, and the many pitfalls scientists can fall into when producing research. It also further proves the point that linking brain size and intelligence is very simplistic; a bigger brain does not necessarily mean a cleverer brain!

Lead image:

The human brain.

Wellcome Images


About this resource

This resource was first published in ‘Inside the Brain’ in January 2013 and reviewed and updated in November 2017.

Cell biology, Genetics and genomics, Neuroscience
Inside the Brain
Education levels:
16–19, Continuing professional development