Brain volume would not have a relevant link with IQ. Instead, its structure and integrity appear to be more important as a biological basis of IQ, suggests a published in Neuroscience and Biobehavioral Reviews.
An international team of researchers, led by Jakob Pietschnig, Michael Zeiler, and Martin Voracek, from the Faculty of Psychology at the University of Vienna, together with Lars Penke (University of Göttingen) and Jelte Wicherts (University of Tilburg), carried out a meta -analysis that examines correlations between in-vivo brain volume and IQ. Based on data from 148 samples comprising more than 8,000 participants, they reported a robust but weak association between brain size and IQ. This association appears to be independent of the sex and age of the participant.
Jakob Pietschnig, from the Institute of Applied Psychology at the University of Vienna, explains that: “The observed association means that brain volume plays only a minor role in explaining humans’ performance on IQ tests.” And he clarifies that although some association is observed, “brain volume appears to be of only small practical relevance. Rather, brain structure and integrity appear to be more important as a biological basis of IQ, while brain size functions as one of many compensatory mechanisms for cognitive functions.”
Differences in brain structure appear to be largely responsible for species differences in cognitive performance. Among Homo sapiens, there are indications of a larger association between IQ and brain volume that are equally questionable. For example, differences in brain size between men and women are well established, giving men comparatively larger brains than women. However, there are no differences in overall performance on IQ tests between men and women. Another example is individuals with megalencephaly syndrome (enlarged brain volume) who typically perform lower than the average population on IQ tests.
“Therefore, structural aspects seem to be more important for cognitive performance among humans as well,” concludes Pietschnig.
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