Human intelligence cannot be explained by the size of the brain's frontal lobes, say researchers. Research into the comparative size of the frontal lobes in humans and other species has determined that they are not -- as previously thought -- disproportionately enlarged relative to other areas of the brain, according to the most accurate and conclusive study of this area of the brain. It concludes that the size of our frontal lobes cannot solely account for humans' superior cognitive abilities.