We only use 5% of our brain, etc..

Kevin Spencer kspencer at iti.org
Thu Jan 20 16:18:40 EST 1994

jonah at ugcs.caltech.edu (Jonah Michaud) writes:

>If this is a faq I apoligize..  From the LA Times, Jan 11, _The Mystery of
>Memory_, by Steve Emmons:

>  "The brain is an unimaginable jumble of electrical circuits.  Each of 10
>billion brain cells connects with 50,000 others.  One square millimeter of
>cortex, the crinkly surfaced dome of the brain, contains 80,000 brain cells,
>making the cortex the most complex electronic circuit board on Earth.
>  This means the brain's memory storage capacity is effectively unlimited.
>You'd need many more than one lifetime to fill it up."

This is a general beef I have about statements like the one above, not a
flame on anybody:

Why do people insist upon comparing the brain, an extremely complex
dynamical system, to digital computers?  Neurons are *not* transistors.
The cortex is *not* a circuit board.  The "memory" of a brain is *not*
the same thing as computer "memory".

IMHO in the years to come people will stop comparing neural systems to
computers, as we begin to understand the nature of "computation" in
complex systems like the brain.  It's understandable how the brain/computer
metaphor got started, but it's very limited.

[stuff deleted]

>Is the statement "we only use 5% of our brain" true?  And does it refer to
>an untapped memory capacity?  Is it consistent with natural selection- is
>there a reproductive advantage to having excess "brain" or memory capacity?
>Or does natural selection simply have no say in brain capacity above that
>needed for hunting/gathering?

I don't think that just because the performance of subjects (animal and 
human) in certain experimental tasks isn't significantly degraded by loss
of X percent of neural mass doesn't mean that that portion of the brain
wasn't being used for anything.


Kevin Spencer
Cognitive Psychophysiology Laboratory and Beckman Institute
University of Illinois at Urbana-Champaign
kspencer at p300.cpl.uiuc.edu / kspencer at psych.uiuc.edu

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