After Albert Einstein died, his brain underwent an autopsy. In particular, it was found that he had an abnormally thick corpus callosum, the part of the brain known to link the right and left hemispheres. With some attributing the thickness of this part of his brain to his intelligence, does having a larger corpus callosum really make someone smarter?
There seems to be a lot of conflicting research on the issue. One study for example conducted by the University of California in 2007 found that greater thickness of the posterior areas of the corpus callosum does indeed correlate with a higher intellect across all measures of IQ. Studying 28 men and 34 women using computational mesh-based methods, they concluded that a thicker corpus callosum likely leads to more efficient inter-hemispheric communication, something that may benefit the processing and integration of information.
However, another study, conducted in 2008 by Australian researchers found that this may not be the case- or at least among teenagers and young adults in their early twenties. In their study, they found that opposite to previous findings, posterior regions of the corpus callosum that were smaller in area were more associated with higher estimated IQ performance than those with larger areas. They also noticed that as people got older, their corpus callosums tended to grow larger, something that may or may not have impacted the results of their and others’ studies.
Other research has found different results again- results that may even conflict with notions of the corpus callosum affecting intelligence at all. One meta-analysis conducted in 2018 for example, found that only negligible changes in IQ were observed in individuals who underwent a callosotomy to subdue seizures caused by epilepsy. Although in these procedures the corpus callosum is not removed, it is severed in an attempt to limit the spread of seizures from one side of the brain to another.
All in all, the study found that those scoring at least averagely on IQ tests prior undergoing the procedure saw average decreases of 5.44 points, while those who scored below median levels only saw a change of 1.1 points on average. The researchers thus concluded that, although the corpus callosum may have some impact in overall intelligence, it is likely negligible in a more general context.