MOTION MOUNTAIN

250 7 the story of the brain
Ref. 227
Ref. 228
n=10 2 ,f=6, this gives
M writeonce ≈10 16 bit≈10 6 GB . (96)
Structural brain changes are measurable. Recent measurements confirmed that bilingual
persons, especially early bilinguals, have a higher density of grey mass in the small parietal
cortex on the left hemisphere of the brain. This is a region mainly concernedwith
language processing.Thebrain thus makes alsouseof structural changes foroptimized
storageandprocessing.Structurechangesarealsoknownforotherpopulations,suchas
autistics,homophilesandhyperactive children. Intense and prolonged experiences duringpregnancyorchildhoodseemtoinducesuchstructuraldevelopments.
Sometimes it is claimed that people use only between 5 % or 10 % of their brain capacity.Thismyth,whichgoesbacktothenineteenthcentury,wouldimplythatitispossible
to measure the actual data stored in the brain and compare it with its available maximum.Alternatively,
the myth implies that the processing capacity can be measured and
compared with an available maximum capacity.The myth also implies that nature would
develop and maintain an organ with 90 % overcapacity, wasting all the energy and materialtobuild,repairandmaintainit.Themythiswrong.Atpresent,thestoragecapacity
andtheprocessingcapacityofabrain cannotbemeasured,but onlyestimated.
The large storage capacity of the brain also shows that human memory is filled by
the environment and is not inborn: one human ovule plus one sperm have a mass of
about1 mg, which corresponds to about3⋅10 16 atoms. Obviously, fluctuations make it
impossible to store10 16 bits in these systems. In fact, nature stores only about6⋅10 9 DNA
base pairs or12⋅10 9 bits in the genes of a fecundated ovule, using3⋅10 6 atoms per bit.
In contrast, a typical brain has a mass of 1.5 to2 kg and contains about 5 to7⋅10 25 atoms,
which makes it as efficient a memory as an ovule.The difference between the number of
bits in humanDNA and those in the brain nicely shows that almost all information stored
in the brain is taken from the environment; it cannot be of genetic origin, even allowing
for smart decompression of stored information.
In total, all the tricks used by nature result in the most powerful classifier yet known.*
Are there any limits to the brain’s capacity to memorize and to classify? With the tools
that humans have developed to expand the possibilities of the brain, such as paper, writingandprintingtosupportmemory,andthenumeroustoolsavailable
to simplify and to
abbreviate classifications explored by mathematicians, brain classification is only limited
by the time spent practising it. Without tools, there are strict limits, of course.The twomillimetrethickcerebralcortexofhumanshasasurfaceofaboutfoursheetsofA4paper,
achimpanzee’s yieldsonesheetandamonkey’s isthesize ofapostcard.It isestimated
thatthetotalintellectually accessiblememoryisoftheorderof
thoughwithalarge experimentalerror.
M intellectual ≈1 GB , (97)
* Also the power consumption of the brain is important: even though it contains only about 2% of the
body’smass,it uses25%oftheenergytaken inbyfood.
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net