Why was Albert Einstein or Leonardo da Vinci a genius? People generally think that they had bigger brains, but I've done some research recently and I don't think that is necessarily true. I found a 2004 study that showed that the size of the whole brain might not be that closely related to high intelligence. In this study, scientists found that the volume of “gray matter” in a section of the cerebral cortex had more influence on intelligence than on the total volume of the brain. In fact, some scientists think Einstein's brain was smaller than many “normal” brains, but it had fewer fissures and more connections. Intelligence is a difficult quality to define and it appears that why some people are more intelligent than others might also be more complicated than it first appears.