Larger Brain Does Not Equal Higher IQ, Study Shows

An international research team, led by Jakob Pietschnig, Michael Zeiler, and Martin Voracek of the University of Vienna, have revealed that - contrary to the age-long belief that a larger brain means higher IQ potential - brain size has a positive relation to brain power, but does not guarantee a high IQ.

The team, alongside Lars Penke of the University of Gottingen and Jelte Wicherts of Tilburg University, published their analysis examining the correlations between IQ and in-vivo brain volume in the journal Neuroscience and Biobehavioral Reviews.

In a study that involved more than 8,000 participants, the researchers took data from 148 samples, and reported a weak association between brain size and IQ, independent of the gender and age of the participants, according to a release.

"The presently observed association means that brain volume plays only a minor role in explaining IQ test performance in humans. Although a certain association is observable, brain volume appears to be of only little practical relevance. Rather, brain structure and integrity appear to be more important as a biological foundation of IQ, whilst brain size works as one of many compensatory mechanisms of cognitive functions," Pietschnig said.

Long has the belief stood that brain size is related to IQ, as first expressed in the 1830s by German physiologist and anatomist Friedrich Tiedemann. With the amount of brain-imaging technology available in the modern world, the assessment of this claim is finally possible.

"We show that although the positive association of brain volume and IQ seems to be robust, its strength has been overestimated in the literature," the researchers said. "While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as a necessary cause or isomorphic proxy of human intelligence differences."

The importance of brain structure versus brain volume, when comparing species or individuals, is very evident, and the structure of the brain appears to be mainly responsible when considering to cognitive performance.

Similarly, with human beings, the indications of brain size being related to high IQ are questionable. Men often yield larger brains than women, but there are no statistical differences in global IQ test scores between men and women.

Additionally, those who experience megalencephaly syndrome, or an enlarged brain, often show lower IQ results than the average person. The researchers ultimately concluded that although there is a relation between brain size and IQ, there is no guarantee of a high IQ due to a large brain.

"Therefore, structural aspects appear to be more important for cognitive performance within humans as well," Pietschnig said.

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