I&#x27;ve read this report before, mainly it was used as a reference doc when debating others about the 10% brain myth. See here, as it directly references the 126 IQ example under &quot;John Lorber and hydrocephalus&quot;: <a href="http:&#x2F;&#x2F;johnhawks.net&#x2F;weblog&#x2F;reviews&#x2F;brain&#x2F;development&#x2F;ten_percent_brain_myth_2007.html" rel="nofollow">http:&#x2F;&#x2F;johnhawks.net&#x2F;weblog&#x2F;reviews&#x2F;brain&#x2F;development&#x2F;ten_pe...</a><p>It appears the amount of white matter in the brain can vary wildly without having a large effect on cognition (as with the 126 IQ example). Usually it&#x27;s the cerebral cortex, the outer, wrinkled brain layer that matters most. Humans have more neurons in this region than any other mammal by far.<p>This squares with the original article, which argues the absolute number of neurons in the cerebral cortex is more accurate for measuring cognition than sheer brain size. So we might derive that brain mass lost due to hydrocephaly is not nearly as important as the cortex neurons retained.