The corpus callosum is significantly larger in adult musicians than in adult nonmusicians, but a closer look finds that it is really only larger in musicians who started practicing before they were seven. Since the initial publication of these findings in the 1990s, research has uncovered a number of other regions of the brain that are larger in musicians than in nonmusicians, but only if the musicians started training before a certain age. Many of those regions are related to muscle control,
