Naked Science Forum
General Science => General Science => Topic started by: chris on 12/02/2010 08:07:44
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I was asked on the radio today how much, in terms of information, the brain is thought to be able to hold in megabytes, gigabytes or (more optimistically) terabytes.
I have to admit that I haven't the foggiest; I suggested that it's also quite hard to know because the brain is effectively indulging in information "compression" in much the same way that a TIFF image can be converted into a jpeg or a wav file can become an MP3 to save space. Consequently memory storage and retrieval in a human is not faithful, so it's hard to know how much genuine capacity is there.
Any ideas?
Chris
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Approaching it from a computing perspective, and hazarding some really wild guesses, I would say we might store as much as 100,000 "objects" in our brains. An object could be all sorts of things, and some of those objects are means to associate multiple objects into compound objects.
We could make a guess about the average amount of storage required for each object. I suspect it's not all that large, because we compress information in a way that is fairly "lossy". So, making yet another wild guess, we might assume something like 100,000 "bits" of information per object.
The total would therefore be 10,000 Megabits of storage, or the equivalent of about 1.25 Gigabytes. So we could put it all, quite easily, on a small flash memory.
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I think 1.25Gb is an underestimate.
1.25 Gb could hold about 50 albums worth of pop tunes (in MP3 format).
I think if you played a few seconds of a tune to someone who had a 50 album music collection I think they would be able to tell you whether they had heard it before*, if so the the human brain must have more than 1.25 Gb storage, coz they can remember 1.25Gb of music and lots of other stuff besides.
(* they may not be able to name that tune but could tell you if it was in their 50 album collection)
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I think 1.25Gb is an underestimate.
1.25 Gb could hold about 50 albums worth of pop tunes (in lossy MP3 format).
I think if you played a few seconds of a tune to someone who had a 50 album music collection I think they would be able to tell you whether they had heard it before*, if so the the human brain must have more then 1.25 Gb storage, coz they can remember 1.25Gb of music and lots of other stuff besides.
(* they may not be able to name that tune but could tell you if it was in their 50 album collection)
My estimate could be very low RD, but I don't think we store music in anywhere near the definition that MP3 encoding allows. (If we did, why would we need MP3 players?) It's probably a lot more like a super compact MIDI encoding format which is orders of magnitude less than MP3. Also, I suspect we don't store repeat sequences at all. I would think the human brain is really good at eliminating any and all redundant information. The lack of redundant information makes it much simpler to access information, and that is what the brain is really good at. Computers, on the other hand, can store infinite amounts of stuff, but their access methods are very primitive compared to brains.
Similarly with images; we might be able to recall them in some detail initially, but it does not take long before we discard most of the detail and only remember the things that our brain seems to consider important. If that were not the case, eyewitness accounts might actually be reliable whereas it is well known that they are extremely unreliable.
I suspect that when we think we are remembering something we are recalling certain key elements while simultaneously doing an amazing amount of interpolation to fill in details which we then think we actually remembered [:D]
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If the storage (and 'execution') involve some long range quantum effects, (kind of entanglements effects), then its capacity of storage and computation is much much larger.
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Actually, the brain contains certain chemicals which make us forget. (This was shown by the Israeli physiologist who identified THCP in cannabis, which plays a similar role) I saw an interview with him some years ago where he was asked why this chemical should even be in our system. His answer was "would you want to remember every face you see on the street every day?" Evidently, the potential for remembering things is almost boundless. One of the savants remembers everything he reads. He reads 3-4 books a day and has for most of his life. He is in his 50's so how many bytes in "War and Peace??" Add to it that he is a human calculator and can tell you what happened 687 years ago on the 235th day of the year - there is a LOT of information stuffed in his brain.
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I think a total of 100000 objects is way too low: if one just thinks of different words, there are > 170000 words that are in current use in the OED, as well as > 45000 obsolete words, and I suspect that some of the compilers recognise most of them, and that's just counting different words. When you then add a person's skills and memories we're getting way past 100000 different objects.
There are > 100000000 neurons in the human brain, according to some estimates, so that gives some idea of the scale of complexity, but even assuming that figure is accurate you have to remember that both storage and processing takes place in the brain.
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If each neuron only stored "one bit", 100 million neurons is only the equivalent of 12.5 Megabytes.
However, let's say a neuron is capable of encoding 256 "states", that would boost our capacity all the way up to 100 Megabytes.
BTW, the Old and New Testaments combined are less than 800,000 words, and many of the words are used repeatedly. Lets say there are 4,000 unique words in the Bible, so each word can be represented by a 12 bit code. (12 bits encodes 4096 possible states)
Total number of bits to store the Bible = 9.6 MegaBITS = 1.25 MegaBytes. Small enough to fit on an old fashioned floppy disk! It is quite possible to use far more sophisticated compression techniques that could reduce that number significantly.
The point is, if you want to put enough energy into clever compression techniques, it really does not take all that many bits to store lots of information. It's a trade-off between storage/retrieval time and capacity. I don't believe we are overendowed with capacity, but we have far more efficient compression capabilities than state-of-the-art computers. I believe our brains are quite capable of inventing new compression techniques that are adapted to the context of the information. Even when we have captured the data, our brains keep trying to refine the compression and discard redundant or obsolete information (this may be what we are doing while we are sleeping.)
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I think it's pretty clear that information (data) isn't stored in the brain in the same way that we store data digitally, but some of the digital methods that are used may shed some insight.
For example, we can normally store one of 256 different values in just eight bits, but that means just using those eight bits once, for the single value that's being stored. However, if we add seven more sets of eight bits we can arrange them two dimensionally, like the squares on a chessboard, and not just read across each set of eight bits but also down each set of eight bits; instead of just storing eight individual values from eight sets of eight bits we've now doubled it to sixteen.
Then of course, not every bit of data needs many bits to be stored: single boolean (true/false) values only need a single bit, of course.
And there are even more complex ways of organising a given number of bits, not just limited to their dimensional arrangement, but by using different sets of bits as pointers to different combinations of data bits from different sets of data bits, so that each data bit may by compounded with other non-directly related data bits to store yet additional values, with each individual data bit effectively being part of many different simultaneous values.
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I agree with you Lee. I'm sure the brain is much more analog than digital, so it's difficult to draw any meaningful comparisons between brains and computers. We know how computers work but we only have glimpses into the operation of brains, and they certainly don't operate along the lines of conventional computers.
It's only a hunch, but I suspect our brains are extremely good at compacting stored information so that they are able to apply maximum energy to solving the next problem they encounter. From an evolutionary standpoint that would make some sense. Our brains are already very large in proportion to our bodies, but if we filled them up with lots of stored information, we would have little room left for processing unless we grew even larger brains. But that would bring significant costs.
Slightly off topic, but related, the fact that our large brain to small body mass ancestors survived at all seems to be something of a fluke. Genetic research indicates that we are all descended from a remarkably small population. If I remember correctly, it is thought that, for a period, the number was in the hundreds of individuals.
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Wow! 1.25 gb. So, human can store 12.5 million recorded chess events(in algebraic chess notation)