Humans use 10% of brain... true?

Jaimie Polson jaimiep at
Wed Aug 25 22:47:37 EST 1999

In <7q2135$j35$1 at> "Martin Knopman" <mknopman at> writes:

>henrik at wrote in message <7pun9k$9bs$1 at>...
>>Is the common (pseudo-scientific) myth that humans only use 10% of
>>their brain true?

>I don't even know what this question means!  You have some notion of 100%
>utilization of the brain?  Can anyone cite a study, or conjecture, that the
>computational capacity of the normal human brain (outside of newly created
>and acquired linguistic devices?) is x.  And has anyone ever even come up
>with an estimate for the average (?) computational work done by some average
>brain, in some average situation, after an average amount of sleep, thinking
>some average thought, within an average emotional environment, ... I think
>that it's even hard to determine %100 utilization of many simple mechanical
>machines - different contexts yield different answers, not to mention the
>unknown productive contexts.

Um, the brain does a lot more than "compute", think thoughts etc.  And most of
the brain's functions work pretty well, even if you haven't had an average
amount of sleep.  I think the question is pretty simple.  You have 100 neurons
in your brain and you use 100 of them (for what ever function).  QED 100%
usage.   You use 10 of them, then 10% usage.  The question is do some neurons
just sit around and never do anything.  The answer.  I dunno.  I suppose
this kind of statement comes from knowledge of various insults to the
brain - small stroks, brain surgey, injury etc that do not appear to effect
our functioning.  And also that it is well known that the number of
neurons in our brain decreases continuously over our adult life.  So
therefore, we only seem to need a proportion of our neurons to function
properly (although I don't know where the 10% comes from).  But the, I 
suspect this comes from redundancy in our brains, rather than simply
some neurons are not ever active.

<original poster>
>>How is this coherent with evolution theory (the extinction of useless

I don't think this is a good definition of how evolution works.  Species/
lines prosper over others when they have some advantage.  But if something
is neither an advantage nor disadvantage, then it won't make a difference
to that specie's survival, so there will be no reason for that feature to
be lost.


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