My lecturer said that theory (man only uses 10% of his brain) is obsolete. Just like the tongue-map theory, you know, the one that says this part of the tongue detect sweetness, this one sourness etc.

I dont know what the latest brain stat is. 20%? 80%? In the past, it was thought that you can remove certain part of someone's brain and that person can still live. Recent study says every part of human brain has their own task, thus removing ANY parts of the brain will reduce a portion of human ability or skills.

For example; the prefrontal lobotomy. In ancient times human believe that there are something inside the skull that is responsible for evil and illness. So they crack open a little hole in the patient's head to "cleanse the evil." In 1940's the procedure was practiced in US, especially by a certain Walter Freeman who believe he can "calm" schizophrenic patients by lobotomizing them. It did calm some individuals, but often the result was often disappointing.

Human biology is only beginning to make its mark in the world. What you learn now could be obsolete by next year. Maybe tomorrow they'll announce "We found out that XXX was responsible for dreams and imagination. Therefore when waking, you use Y% of your brain, but when you're (day) dreaming, it's Z%."

If you remove the stats, I'd say we are unable to be able to use certain part of the brain because;

- brain degenerates as we grow older. Prove: there's a certain frequency of sound that only people below 20 years old can hear. This is because the part in the brain that corresponds to the said frequency degenerates as one age.

- we don't utilize enough brain muscle to use certain part yet. If you go to gym and lift weight everyday you'll gain weight and muscle. If you think/perform certain task frequent enough the neurons will establish lots of strong connections in the brain aka using more part of the brain.

Maybe we DOES use all of the brain function, just not all at once. When your dreaming your motor sensory are at rest. When you're thinking numbers your imagination might be in stand by.