How do brains produce intelligence

Intelligence: Smart people have bigger neurons

The result someone gets on an IQ test appears to be related to the size and speed of the neurons in their brain. This is what a team led by Natalia A. Goriounova from the Free University of Amsterdam reports in the specialist magazine "eLife". The scientists examined the nerve cells of 46 people whose brain tissue had to be removed because of a tumor or epilepsy. Her particular eye was on the size of the cells and the complexity of the dendrites, the processes with which neurons receive electrical signals from other cells. They also measured how quickly the cells were able to transmit these signals to the cell body, and then compared the data with the result of a standardized IQ test that all patients had to take as part of the preparation for the operation.

Goriounova and her colleagues discovered that nerve cells from subjects with a higher IQ had longer and more complex dendrites on average. In addition, the cells were able to pass on incoming stimuli more quickly. With the help of a computer model, the researchers demonstrated that the neurons of the smarter test subjects can process a larger amount of signals and pass on more detailed information to their neighboring cells. At the level of a single neuron, this may seem unimpressive. However, given the fact that our brain contains around 100 billion such cells, the effect quickly adds up, according to the researchers.

This article is contained in Spectrum Psychology, 3/2019 (May / June)

Neuroscientists have long suspected that the key to high intelligence lies in lush dendrites, among other things. For example, a team led by Mark Harnett from the Massachusetts Institute of Technology recently showed that the nerve cells in the human cerebral cortex, because of their size, have more computing power than that of a rat. Proving a direct connection between the cell size and the IQ of individual people has so far been difficult for methodological reasons.