Neurologist Barry Gordon describes the myth as laughably false, adding, "we use virtually every part of the brain, and that [most of] the brain is active almost all the time".
[1] Neuroscientist
Barry Beyerstein sets out seven kinds of evidence refuting the ten percent myth:
[12]
- Studies of brain damage: If 90% of the brain is normally unused, then damage to these areas should not impair performance. Instead, there is almost no area of the brain that can be damaged without loss of abilities. Even slight damage to small areas of the brain can have profound effects.
- Brain scans have shown that no matter what we're doing, our brains are always active up to 45%. Some areas are more active at any one time than others, but unless we have brain damage, there is no one part of the brain that is absolutely not functioning.
- Evolution: The brain is enormously costly to the rest of the body, in terms of oxygen and nutrient consumption. It can require up to 20% of the body's energy—more than any other organ—despite making up only 2% of the human body by weight.[13][14] If 90% of it were unnecessary, there would be a large survival advantage to humans with smaller, more efficient brains. If this were true, the process of natural selection would have eliminated the inefficient brains. It is also highly unlikely that a brain with so much redundant matter would have evolved in the first place.
- Brain imaging: Technologies such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) allow the activity of the living brain to be monitored. They reveal that even during sleep, all parts of the brain show some level of activity. Only in the case of serious damage does a brain have "silent" areas.
- Localization of function: Rather than acting as a single mass, the brain has distinct regions for different kinds of information processing. Decades of research have gone into mapping functions onto areas of the brain, and no function-less areas have been found.
- Microstructural analysis: In the single-unit recording technique, researchers insert a tiny electrode into the brain to monitor the activity of a single cell. If 90% of cells were unused, then this technique would have revealed that.
- Neural disease: Brain cells that are not used have a tendency to degenerate. Hence if 90% of the brain were inactive, autopsy of adult brains would reveal large-scale degeneration.
Another evolutionary argument is that, given the historical risk of death in childbirth associated with the large brain size (and therefore skull size) of humans,
[15] there would be a strong selection pressure against such a large brain size if only 10% was actually in use.
We already use all of our brain power but not all at the same time.
