On a serious level, it makes sense that humans only use ten percent of their brains. We have the most complex and multitasked brains and bodies of all of the animals. Our brains are instrumental to regulating or at least paying attention to thousands of chemical, electrical and other processes that keep us alive and active in a wider variety of activities than any other animal.
The problem lies in the expectation that ALL of our brain should be used in intellectual activity, when that is not true. Much of our brain obviously is tasked with regulating our complex systems. The amount of brain that has to be dedicated to our reading, learning, communicating, emotions, and so on apparently is very little, even in the smartest of us.
On a situational level, it is clear that we often do not use even the expected 10 percent of our brains to think! We are often operating in “twilight” mode as we do repetitious tasks, are not learning new concepts, or are not thinking about things. We are good for such things as “road narcolepsy”, where we snap out of it on a long but routine drive and cannot remember most of it! We do repetitive tasks on our computers, too, using knowledge that we already have to crunch our bank account numbers, enter raw data and chat endlessly in groups that are just interested in keeping the conversation flowing.
On other levels, we wonder if ANY thinking is going on! Some of the chatter on the news networks, the behavior in reality television shows, and the dumb stunts that people pull when they are under the influence of alcohol or mood altering substances causes us to wonder if the brain has atrophied to the point where only the bodily functions are operating. Perhaps the brain has to channel its resources to keeping the inebriated body from death from poisoning or accident.
As for alcohol, marijuana and other drugs, the originators did not call those substances “dope” for nothing! To watch a person attempt to make change, pay attention in class, or even complete a basic business transaction while on drugs is a view into the world of our brains in shutdown mode.
In summary, there was no promise that all of our brains were available for intellectual use or for thinking. But the things that we do to shut down the part of our brain that does think supports the idea that we only have 10 percent to work with on our best day!