Dutch researchers have uncovered a possible new biological basis for intelligence: People with higher IQs appear to have bigger neurons as well as brain cells that are capable of withstanding electrical signals at higher frequencies than low IQ individuals. These findings expand the list of possible biological factors involved in intelligence.
The study is available on the pre-print server bioRXiv and focuses on the correlation between IQ and a cellular structure in a small number of tested people. The team asked 35 patients that needed brain surgery for either a tumor or severe epilepsy for a tiny sample of healthy brain tissue. They also completed an IQ test before the operation.
The samples were taken from the temporal lobe of the brain, which is involved in the processing of sensory inputs, the retention of memories, and language comprehension. The team discovered that the size of neurons correlated well with IQ test results. But it wasn’t just that – these bigger cells have more dendrites, the connections to other neurons, and they are longer.
The team also tested the ability of these neurons to transmit electrical signals. They used a current at different frequencies to look for correlations between one's IQ and cell behavior. Neurons from those with a higher IQ coped better with higher frequencies than those with a lower IQ, whose neurons became slower as the frequencies increased.
The research suggests that bigger cells, longer and more numerous dendrites, and the ability to cope with faster signals give people the ability to process information more quickly. This speed advantage is then witnessed in reaction times and is measured by the IQ tests.
This piece of research is extremely intriguing, but it is not the end-all, be-all of the biological causes of intelligence. First of all, 35 people is a very small sample size. Researchers have also previously found that grey matter thickness and activity in the temporal and frontal cortex are linked to higher intelligence. Genetics might also play a small role, and it is unclear whether these biological factors are a cause or consequence of higher intelligence.
When it comes to assessing intelligence with standardized IQ tests, we need to remember that what’s in your skull is not the only thing that matters. Other factors – such as health, education, and upbringing – play a role in doing well on an IQ test, which it should be noted some think are not the best indicator of intelligence.
[H/T: New Scientist]