If brain size relative to body size determines IQ, the venerable shrew would be the smartest creature on the planet. But it doesn't, and it's not, and scientists from Austria, the Netherlands, and Germany have combed through 88 studies with more than 8,000 participants to confirm in the journal Neuroscience and Behavioral Reviews that when it comes to intelligence, brain size simply doesn't matter. "Although a certain association is observable, brain volume appears to be of only little practical relevance," says Jakob Pietschnig from the Institute of Applied Psychology at the University of Vienna. The researchers write that "positive associations between human intelligence and brain size have been suspected for more than 150 years." Why the long-held belief in such a link despite a lack of concrete evidence for it?
It may partly be the result of publication bias, reports ScienceAlert. This means that journals more readily publish findings with strong links between subjects than weak or inconclusive links. And that's all that Pietschnig and his team found when they reviewed published and unpublished studies—a link too small to have any discernible effect. "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 adds. This helps explain why men, who tend to have larger brains than women, do not perform better on IQ tests. To be small-minded, then, should be construed in only a metaphorical sense. (Check out what has been hiding in brains for centuries until this year.)