On 11 Mar 1997, F. Frank LeFever wrote:
> In <5fvtvq$1rg at News.Dal.Ca> ak057 at chebucto.ns.ca (Shane Markle) writes:
>> >
> >I recently heard of a calculation of the general amount of information
>> >stored in a human brain, represented in bits, and need to know what
> that
> >capacity is. If anyone has the figures, would they please email them
> to
> >me at aa642 at torfree.net? It's needed to settle an
> argument/discussion.
>[snip]
> (1) no one knows how info is stored in the brain (I repeat: no one), so
> one cannot calculate it rationally--e.g. by estimating the number of
> cells and their interconnections and their dendritic spines and their
> multilevel (non-discharge) graded states, etc., etc., etc.
Another problem may be that no generally accepted model of memory exists
yet.
>> (2) no one, so far as I know has approached this problem "empirically",
> e.g. by extraplating from behavioral samples, except in a very limited
> realm. Last week, at the NY Academy of Sciences (Linguistics Section
> meeting), Steven Pinker of MIT reminded us of studies in which people
> sampled a large dictionary (e.g., every 10th word on every 5th page) to
> form vocabulary tests, yielding estimates of the total vocabulary of
> high school students. If you can think of a way of randomly sampling
> EVERY POSSIBLE KIND of info, maybe you can come up with an estimate of
> how much your subjects have "stored"..
>
At least it should be possible to obtain a minimum value.
One can distinguish between active and passive word knowledge. Obviously
passive word knowledge is larger than active. Since the passive word
knowledge can be as large as 100 000 words (look at Webster; for Scrabble
enthousiasts or Scholars maybe even higher, up to 300 000?) one has at
least a minimum value. If one - like myself - has been so unfortunate as
myself of having been forced to learn several foreign languages, the
passive word count increases further. One has also the ability to
recognize names of people and of geographical data. I guess that that
results in a value of about 500 000 words (~ 10^6). Assuming an average
word length of 10 letters on obtains an estimate of ~ 10^7 characters.
Again assuming that one character is ~ 100 bits, one obtains ~ 10^9
bits. Since the brain has a volume of about 1 L, this means a minimum
density of 10^6 bits/ cm^3.
This is all a rough guide, and the argument can be refined. There must be
much data available, for instance on word frequency; data on visual
and sound recognition may be also be available.
In recognising slightly changed faces, for instance, how different can
they be so that people still recognize them as the same face? If you can
quantify such a 'resolution', one might be able to estimate the size of
'different recognizable faces space' : this would give an upper value.
Anthonie Muller
The Thermosynthesis Home Page
http://www.ed.ac.uk/~awjm
