My Biology teacher had recently said that we actually use only like 4-5% of our brain capacity. Is she correct?[?] I think that we are using close to or 100% of our brain capacity. Because the brain uses the highest amount of energy in our body, so i doubt that evolution of such a big brain happened for millions of years, just so that it can guzzle so much energy and provide only a 4-5% output. Highly illogical of a natural selection which will ruthlessly expel such an opposition of efficiency. *please correct my bio wherever applicable.