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Ask Slashdot: Storage Capacity of the Human Brain?
STUR
submitted this interesting question:
"Since humans are supposed to have such great minds,
I would like to know how much storage capacity a human
brain has compared to, let's say, a computer's hard drive.
Hrm... If the capacity is high enough, do you think that
computers of the future could possibly use the brain as a
sort of hard drive or ram chip? Just a little something
to think about." I've heard that the brain uses a form
of holographic storage to archive its information and I don't
know if there is a direct mapping to that and say terabytes
of information (warning: I am not an expert!). What do
all think?
It's a lovely story, but not a very good model. Take for example your assertion that "most people can't remember details very well." Then consider that any functional 5 year old retains a vocabulary of thousands of words, the rules for manipulating them in communication, and (in the case of most 5 year olds I've known) knows the TV schedule for any day of the week for multiple channels. I can still remember the phone number and address of the house I grew up in - while event memory may be fuzzy and biased, things like numbers (how many physical constants do you remember the value of for example), words, spellings, C language reserved words are all stored very crisply and accurately, with excellent recall speed. It doesn't seem to me any of these things are necessarily linked to some overarching gestalt. I suppose maybe I remember "printf" because it's "print" with an 'f' on the end, and "sprintf" because it's "printf" with a leading 's' and "snprintf" because ... But none of these do I associate with some event (I don't remember what I was wearing the first time I saw "printf" for example), and none of these recollections is in any way fuzzy or approximate.
Another thing no one here seems to be considering is that there are quite possibly multiple memory systems operating in the brain (beyond just the long term/short term pair). Your PC for example has DRAM (core), cache, CMOS setup RAM, video ram,
local ram on adapters, FIFOs, hard drive, floppy drive, CD/DVD, tape - all specialized types of memory to meet particular needs, and each with a multitude of storage formats, and each produced via an evolutionary process just like the development of the human brain.
We have externally stimulated sensory memories, internally generated emotional memories, memories of gross detail (landscapes, clothing, people), detailed, crisp memories of all kinds of specific data, and probably lot of other categories too. We perhaps don't remember the details of specific events well all of the time, but compare that to the ability to recognize facial characteristics - the resolution in that subsystem is phenomenally good.
Contrast all of this to the claim that most people can't remember details well - obviously that's over-generalized to the point of absurdity on the basis of quality or quantity of details the average person can remember. What kind of details specifically?
I was gonna put a sig on here, but I forgot what it was.
When I was taking my grade 11 biology course, we studied genetics. Something that came up was the fact that your genes could, and in fact did, change. A real question that came up, which my teacher refused to answer (said to go to the religion teachers) was one involving different chromosomes. Say I, a male, was born with two 'X' chromosomes. I would be a different physical person - obviously, a female - but would I be the same person? After all, if the soul or consciousness or what-have-you is created or metred out or whatever when you're concieved, would the prescence of a couple of extra genes make that large of a difference?
A very, very good book to read on what you wrote about is "The Terminal Experiment" by Robert J. Sawyer. It involves a scientist who has created the technology sufficient to make an exact copy of the human brain (and consciousness), and can also modify it to suit his requirements. I reccomend checking it out if you're at all interested in the theology of biology and consciousness - it is a near-future science-fiction book, if you're interested.
E-mail me if you wish to talk further.
Posted by FascDot Killed My Previous Use:
Surely that's a typo. I know *I* have more bandwidth than that. Heck, I've got more than that for audio alone.
Think about it: Human speech doesn't sound natural on playback unless it's around 44kHz. That's 44 THOUSAND cycles per second. Of course, we're just talking processing so far, but people with "photographic" memory can store this information perfectly which means fast storage capacity.
As for the 20 questions proof: This assumes that the item is randomly chosen. It also assumes that the person choosing picks a specific object that they have stored rather than a general class. ("I'm thinking of the third flowerpot from the left in the workshed behind my mother's house").
--
"Please remember that how you say something is often more important than what you say." - Rob Malda
That's a good article, but I think memory is more involved than that is. First, for 'learning to ride a bicycle', that isn't even where the rest of memory is stored, procedural memory is in the cerebellum, I think, and it stores a lot of precise stuff, like my touch-typing. It's also the reason that we find it hard to remember a song in the middle, because we have to "sing" it from the beginning--it's a procedure.
Second, if I pick up a book I've read a long time ago, it will be familiar. (or if I just see a passage) That recognition is memory, and I've read a lot of books. If I pick up one I haven't finished, I can seek through it and find my place. I don't think 122MB of data could account for even that much information, much less the music I remember (although that might be in my cerebellum, apparently they count it as memeory).
Other than that, their methodology seems pretty sound, I'd just like to know how they got their estimates into bits.
pb Reply or e-mail; don't vaguely moderate.
I guess the storage capacity would depend on what sort of compression our brain uses... Maybe it compresses audio to an MP3 format. Then we wouldn't even need to get a Rio. "Hear once, play anywhere".
Unfortunately that article doesn't deal with the digital memory hogs of sound, smell and vision. Most people have the ability to identify (even if they cannot remember the names) thousands of people, thousands of smells, thousands of voices, and play "name that tune" for thousands of tunes. All the while, they have a working vocabulary of, say, 100,000 words, memories, thoughts and feelings. I realize that our memory is "lossy", but it isn't binary, it isn't digital. If we wanted to store all one person knew on one computer, a gigabyte would not be enough.
I remember reading that the human brain has a storage capacity of approximately 122 MB. It's explained here.
Right... What I maent to say (and didn't make clear) was that the impulse is not electrical at any point, its a chemical single, which is why the time for the impulse to reach the brain is noticeably longer than the time for the "knee jerk" reaction to pull your hand away.
If it was electrical, than even at a miniscule percentage of the speed of light the nerve impulses would arrive far faster than they do.
An interesting side point is that there are a lot of factors that affect the speed of nerve transmission. Researchers have found that high-contrast visual ranges tend to lead to much faster nerve impulse rates and response times, and low contrast visual scenes tend to slow down the impulses. (Which from a practical standpoint means people are not as capable of judging visually the speeds they're travelling at in low-contrast situations like driving in fog...)
I admitted in my content that I was generally talking around my ass... but what I was saying was from a generalized understanding I put together over several years of participating in, and developing research on learning and memory, including a period of time academically studying the evolution of intelligence.
Whereas your response is based on assumptions you make based on false interpretations of your experiences. You claim there is not an experience that causes you to remember what printf is. That's blatently incorrect. Your are able to associate the meaning of printf in that context because of prior experience you've had either with that concept or with concepts related to that. That's why its easy to pick up a third and fourth language when a brain has developed the proper pathways that allow it to associate with multiple languages. That's why its easy to pick up new programming languages. But that's also why you may know fifteen programming languages but be unable to learn a foreign language at all -- because you learn based on prior associations you've made and you don't have those between unrelated areas of knowledge.
In that vein however, some researchers believe that an unusual ability to create those linkages between non-related contexts are one of the causes of extremely high intelligence, partly caused by genetics, but usually among those researchers its attributed to wide-ranging stimulation during the first nine to twenty-four months of live (the first nine being particularly important because unlike every other mammal species, the human brain continues to grow for 9 months after birth).
There can't be differing ways of storing information in the brain because there is only a single construct within the brain -- the only differentiation between areas coming from the points at which there are larger interconnects within the brain, points where there are larger concentrations of neurons that are not necessarily in physical contact with each other (which is why some scientists think the folds in the brain are related to overall species intelligence), and the insertion points of external sensory nerves.
You however, most likely, do not remember nearly the detail you think you do. Very few people naturally develop the ability to do that, although it can be learned. Take for example someone asks what your significant other looks like. The odds are you will pick out and describe certain elemental details, color of the eyes, color of the hair, shape of the nose, but if someone asked if there was a mark below their ear last time you saw them you might not be able to answer that -- because you are reconstructing an image of that person in your head from individual elements you remember -- elements that may or may not be correct.
The more you pay attention to and use those snippets if information, the more other nerve pathways will utilize those elements and other memories will get locked to them. That's why you can remember the phone numbers of the houses you grew up in -- because of all the other memories associated with those specific memories. That's why you can completely forget a long-past romantic rendezvous, yet a fragrance or some sound can suddently bring that back -- because you triggered the "matrix" of nerve firings that held that experience in the context of another memory -- ane externally stimulated memories are FAR more capable of doing that than internally stimulated memories, because of the areas of the brain they tend to reside in and the relatively stronger impulses you tend to get from external sources.
That's why relaxation and meditation help focus -- because they tend to quiet and control those externally triggered cognitive events and allow more attention to fall on internally triggered ones. (And is also why under hypnosis you are both capable of digging up memories more easily AND creating memories easily).
You'll find in lingustics as well that most people do not have a concurrently available vocabulary of thousands of words, in fact 5000 words is a lot even for an adult, you don't need nearly that to get along in society. But the availability of a word at a given instant is largely related to its association with other concepts and word streams. People with larger vocabularies are often more capable of utilizing a larger wordset because they typically are making an effort to use less common words (even if they won't fess up to it).
If you were going to pick out a point of my original posting that was over-generalized to a point of absurdity, there are points that are far more obsurd than the one you picked. The one you picked is in fact one of the most easily documented points I made, and one of the most widely understood scientifically. The methods that cause it to be true are not as well understood, but its validity is not widely doubted.
This is sort of a silly question for Slashdot, since most people are going to be talking out their asses.
That said, (and talking more around my ass, than out it), there isn't any sort of storage figure. Researchers do not have much understanding about how we remember things, but it IS fairly certain that there is no relationship to the way computers store information (ie, the concept of terabytes, etc).
Generally the brain remembers certain aspects of an experience -- wether an external experience, or an internal one. Its believed that the act of experiencing something, or recalling it later starts changing the relative levels at which nerves will fire and accept the chemical impulses from neighboring neurons. (Before anyone starts talking about electrical impuses, those are only conducted within the nerve cell not between nerve cells and its not an electrical impulse as much as a chemical shift within the nerve that changes the electrical potential of the local region while the signal travels down the length of the nerve -- thats why you can have your hand off a hot stove before you actually feel its hot)
So a memory is generally a tangles mess of restimulations of fragments of what happened. Thats why with few exceptions, most people can't really remember details very well, and everyone is prone to manipulating memories. (ie, you read an interesting tale when you're young, later in life you're sure it happened to you or that someone TOLD you it happened to them, and not that you read it) Things like that happen a disturbingly large amount of the time, with everyone. Luckily such errors don't often affect anything serious.. I mean who cares where you heard a story?
That's why things like memory and attention span and personality can be manipulated chemically -- because you can control the way those experiences link up with each other and how the brain reacts to those experiences.
One of the most interesting things I think people find when they really start studying how the brain learns, and stores its experiences is how little actually comes from the senses or memory. (For example, how the brain can only distinguish general colors and shapes beyond a half-dozen degrees off center in your field of view, but you're constantly fooled into thinking you can see more than you really can)
The question with the brain then is how discret these fragments of memories and experiences are, how many times they can crossconnect with others to produce memories without those crossconnects getting so blurred that you get confused about the truth of what you're remembering, and the number of different fragments that make up a given memory.
Most likely no one will have any idea about the answers to those questions until there is a better understanding how a "neural network" arrangement can store and rerecognize patterns of nerve impulses when the "matrix" used is numbering in the millions of cells at a time...
"Anyway, Watson was telling Sherlock about how the Earth had been proven to orbit around the sun, and Sherlock scolded him for telling him "useless information", and taking up space in the attic of his brain that would otherwise be used for storing information about topics relative to crime-solving."
As much as I love Sherlock Holmes, that passage has always disturbed me for two reasons:
1) It seems to me that the brain is more like a muscle than a storage device: the more you use it, the higher its capacity becomes. Although there may be an upper capacity limit, I doubt more than 10 people alive at any given time ever get anywhere near it. Whereas I have observed many, many people who stopped using their brain capacity and, essentially, lost it.
2) It also seems to me that super-capable people (and I am purposely avoiding the words 'smart' and 'intelligent') are often those who have the ability to draw together seemingly unrelated fragments of information into a new and critical insight. If they have never been exposed to the disparate information, they would not be able to make the leap (again I am avoiding the word 'intuitive' although it probably applies).
My 0.02.
sPh
The three necessary comments have yet to be made, so I just thought I'd have to say them.
1) Can it run Linux?
2) How many MP3s can we get on it?
And 3) Does it have a RAID driver yet?
I read somewhere that the brains capacity was on the order of 13 TB. No links to back it up yet...
If you want to back up 13TB, you might start with EMC. We deal with datasets measured in terabytes every day, and are quite adept at backing them up without even taking them offline.
:)
[Yes, I work for EMC--it's a wonderful job.]
I still find it amusing that they made that movie from a 5 page short story.
:-)
Hey, "2001: A Space Odyssey" was made from a short story ("The Sentinel") that was only about five pages, maybe ten. They threw in a scene from another Clarke story, "Take A Deep Breath". (Guess which scene
(Mind, Clarke is (or was) a SCUBA diver, he should know better. (I.e. exhale, don't hold your breath, or you'll risk an embolism.)
Come to think of it, a lot of SF movies are based on short stories or novelettes, rather than full length novels. Too hard to do justice to the latter in the screen time available. "Dune" should have been a mini-series. (And not done by DeLaurentis).
-- Alastair
Actually, human vision is the aspect of the brain that I find most fascinating, partially because my professional specialty is artificial vision. I find it fascinating how much more advanced our biological vision processing is that anything we can achieve artificially.
Several fascinating aspects of human vision processing:
The "raw" "pixel" resolution of the human eye is actually flaberghastingly low, on the order of 200 x 200 pixels (the effective resolving ability of the rods and cones).
However, the human eye "snaps" about 10 - 12 "frames" per second (maximum, in good light) and the brain integrates subsequent frames, each with very subtle positional differences, and compares adjacent "pixels" from frame to frame to assemble an image of dramatically higher resolution. Thousands by thousands of "pixels" when required by the task being performed (e. g. threading a needle or intricate soldering). This is why staring at a small object for some length of time is necessary before we perceive all the most subtle details.
An additional "weakness" of the eye for which the brain performs some amazing processing to compensate for is this: The rods and cones of the eye are "recharged" by flushing a fluid containing rhodopsin across the retina. Rhodopsin is a protein that breaks down and emits a tiny electro-chemical current when struck by photons of light. The speed of the rhodopsin decay is proportional to the intensity of the light hitting it. The retina "recharges" when the previous charge of rhodopsin is nearly depleted. This works out to 10 - 12 times per
second in bright light, much less (down to a minimum of perhaps once per second) in very low light.
Anyway, the flaw in the above scheme is that the "dose" of rhodopsin that each rod or cone receives in any given "recharge" is very poorly controlled. It varies all over the place. This means that the electrical current emitted by any given rod or cone for any given intensity of light from frame to frame is not consistent! So, the brain has to analyze the average current emitted by each rod and cone, over the surface of the retina and over time, and integrate this information to produce and accurate and detailed internal picture inside the brain!
The analogy is this (for all you artificial vision programmers):
Imagine that your boss gave you this task:
We are going to give you a CCD camera with an array of 200 x 200 pixels. We will rapidly vibrate the camera so that by integrating the subtle changes between adjacent pixels you will, after storing 30 frames, interpolate a picture with a resolution of 5000 x 5000 pixels. Furthermore, the brightness value digitized by each camera pixel is going to randomly vary by 200% for any given actual light intensity. Your system has to output a real time image flow at the above resolution and a brightness accuracy of +- 0.01%.
Yeah right!
But this is analogous to what the brain does!
I've always been more impressed by the brain's processing power than by its storage capacity.
Disclaimer: I'm not a neuroscientist, but I've been reading a lot of books on this recently, and there are huge differences between computer and brain storage that make this kind of measure meaningless.
:-)
First, the "write" operation is highly dependent on how you experience an event. You can't be fully, simultaneously aware of every input- the brain is an excellent signal filter, and only processes those aspects of the environment you are focused on. But there's also an "interest" component- even if you are really paying attention an input, the aspects of it that you find important will be what you remember. Example- there was a study where a researcher asked workers in a museum about a particular painting they all saw on a regular basis. No two people described it the same way- some described the colors, others the emotions they felt as a result of the content, still others the execution of the painting and the specific stylistic elements. And what they remembered correlated closely to what it was about the painting they were "interested" in as part of their job- the curator's recollection (style, context, etc..) was very different from the guy who cleaned it (complicated, hard-to-clean frame).
Secondly, a very important aspect of remembering is uniqueness- something distinctive about a memory that allows you to get a "handle" on it later. It's also thought that multiple, similar experiences tend to blur each other and reinforce the common elements between experiences. For example, I can tell you exactly how I get to work and what lanes I prefer to use, but I can't tell you the exact sequence of lane changes I made on any specific trip.
Third, the brain has a very powerful reconstruction mechanism. It's kinda like dinosaur skeleton reconstruction. Just as a paleontologist can fairly accurately reconstruct an entire skeleton from a relatively small number of bones (or bone fragments) your brain pulls together and reconstructs the few bits of a specific experience that were stored and synthesizes a more detailed rememberance from the fuzzier "generalized" remembrances to give you the impression of remembering much more detail than you actually stored.
This all contributes to explaining why it is so difficult for humans to remember "digital" data. For most of us, there's very little that's interesting, unique, or distinctive about the numbers in a sequence. Mnemonists with apparently infinite abilities to recall details generally have a learned or innate mechanism by which they create unique, distinctive symbols for number sequences which make it possible for them to remember them. In the most highly-developed cases, these symbols encompass every sense- sight, sound, taste, texture, smell.
But such people are often cognitively lost in details... they can't deal with concepts easily, and can't abstract over information they have taken in, since they are so overwhelmed by the distinctiveness and richness of the details. As are computers, which know nothing except detail. So the "lossiness" of the human memory actually serves a useful purpose, and is a large part of what makes us "intelligent" relative to a piece of silicon.
Of course, I'd like to have it both ways...
There is a short-term memory of your entire current awareness. The registers often are used to point at these things, whether they be the red car you're avoiding, the smell of that pie you just noticed, or the part of the network topology which you're designing. These are augmented by various short-term memories for particular senses (the guy on the walkie-talkie just said your name, and you can recall several seconds of sound before that even though you weren't paying attention due to the auditory system memory).
There is a long-term memory which is updated after going through various filters. Emotions tend to increase the chances of a memory being stored permanently. Severe trauma blocks storage of memories (severe accident victims can recall details on the scene, but not after rest).
Some memory processing seems to be done during sleep, but the major reason for sleep is to recharge the energy-storing glial cells because vertebrate brains use more energy than the bloodstream can supply (otherwise there would be mammals which never sleep due to the evolutionary advantage that would provide).
Slashdot needs more filters on submitted articles, to point out to editors more about past articles.
The number of hard disk storage bits may be approaching the number of neurons and connections in the human brain, but one bit on a disk has less information than one neuron or synapse. The disk would need at least one link per item, and in many cases multiple links per item. Obviously many bits will be needed to store links per item.
I don't buy the 2bps argument. People with perfect pitch, for example, can tell you in less than 1s what note you're playing on a 88-key keyboard (6.45 bps). Even an average amature musician can tell you the interval between two notes in less than 1 second (3.58 bps). Perhaps the true/false questions that were asked were insufficient to provide the full range of data that is procesed by the brain, partially because of vocabulary limits (how do you describe the "amount" of light, or level of sound, or pitch modulation, without having a tool to measure it? Yet we still can distinguish between really small levels).
Another problem with the 2bps analogy is that you can't capture the entropy of a concept in bits, and that's a major factor in human memory. (Ever crammed for a test in a class you don't understand?)
I also think that some of these other numbers are high. MPEG, JPEG, wavelet, and MP3 compression show that not all the information we store to reproduce something electronically is actually significant to the human mind.
Just my 2c.
First off, although I don't do this stuff day to day anymore, I did do my degree in cognitive science, so this is the kind of stuff we were expected to think about.
/. analogy. Consider a minimal working Linux installation (basic hardware, kernel, shell). Let us say that the system has a 10GB hard disk. It is obvious that most of the HD is almost completely devoid of information, since it has no context, but is just blank. However the portion of the HD that contains the base software is very information rich, but only in the conext of the surrounding hardware (bios etc), and perhaps more importantly, in the context of the wider environment of /.ers and others who know what Linux is and what it can do, and can interact with it.
The question as asked is ambiguous, since a 'hard disk' is an object whose contents have no semantics, just syntax, that is they have no meaning except when interpreted by another entity (you, me, sendmail, etc). OTOH the information that is stored in the brain is a mixture of semantics and syntax that we do not yet understand.
To clarify this I would like to give a very
Now here we have drawn three levels fairly clearly - the HD, the bios and other hard/firmware, and the rest of the world. But in the case of a human brain it is not at all clear where (or if) one can draw these distinctions, so only a complete description can suffice (i.e. we are not able to summarise the state by means of external references)
In this event we can rephrase the question as follows:
Given the required processing capacity, what amount of storage would be necessary to provide the same information processing capacity as a human brain?
Now here we hit astronomical numbers. The question is equivalent (check Turing, Church, etc) to asking how many bits it would require to store a complete description of a human brain at a given instant. This is certainly a smaller number than a precise description of the state of every subatomic particle in a brain (i.e. less than the memory required for a Star Trek transporter), but is still pretty big.
Back of an envelope? A very conservative envelope? If a brain state could be described by the states of each neuron and each connection in the brain, and each of those took 16 bits (which is almost certainly a gross underestimate), and there are ~10^12 neurons and ~10^3 connections each on average (Churchland and Sejnovki, 1992), then that is 16*10^15.
or 16 peta bits
HTH
Matt
10-12 Frames per second seems _unbelievably_ slow to me. I (and most anyone else) can easily see a difference between an image moving at 12FPS or one at 24FPS. Even the difference between 30 and 60FPS is pretty obvious.
I fooled around for six months writing a juggling animator. At the end, I had it so that it could animate at the refresh rate of my monitor (75fps). If I animated the pattern "in real time" (i.e. a cycle takes as long as it would take if it was juggled by a six foot human on earth), the balls moved quickly enough on the screen that without motion blur there was a stroboscopic effect. So, I added motion blur, and was able to retain the 75fps. With other refinements such as subpixel positioning, the animation looked perfectly smooth. Out of curiousity, I reduced the frame rate to 37.5 fps, leaving all of the refinements in place. The difference was subtle, but I and several of my friends that I showed it to could all see the difference.
I don't think this proves that the eye is sampling at a rate higher than 37.5 fps, since the eye/brain could be doing a lot of amazing image processing to achieve an effective frame rate higher than the raw frame rate.
Disclaimer: I know only a modest amount about neuropsychology/theory of computation...
;).
/addressed/. In the brain's case, there may be loads of 'data' stored, its just you cant remember the 'links' needed to actually get to it - ever been caught out by that word you know, but you just cant quite remember? (I know I have ;).
OK, I've thought about this for a while and here goes:
As far as I can tell, there is very little we actually *know* about the brain. It cannot be likened in any definate way to a (theoretically) lossless accurate finite state machine/automaton, so there is no hard and fast way to answer this question. Get rid of that 122 meg estimate - he's obviously talking about something else
Basically, from what I can tell, the brain works _as a whole_ to store any one given 'item of information'. This is unlike a conventional computer that has a specific location to store a specific bit of data.
Any storage device on a conventional computer (as far as I know) uses some sort of definate addressing mechanism to access a particular peice of data.
On the other hand the brain "stores" pretty much everything you experienced, whether you remember it or not. The problem is how it is
The way the brain 'records' experiences is by changing (m)any neorones' receptibility to neighbouring cells as well as those neorones' internal chemical (in)balance. This would give a "random" (hey - never use the 'r' word without the quotes) yet analogue data storage that clearly cannot be enumerated in any definative way to bytes.
I believe it's entirely possible that the brain could even 'record' data in more outlandish methods such as small inductive/capacitive fields and chaotic electrical interference. What is definately known is that the way the brain stores data is probably more than the "just count the number of cells and multiply by ten" way shown in one of the replies. Such a way would be inmature, inaccurate and an insult to the more thoughtful amongst us.
Now, since I've said all that about just how impossible it is to measure the maximum capacity of the brain, what is probably a more practical answer is how much the brain will store on average. This I dont know, though I guess that that would be a question for the psychologists out there - and maybe thats where the 122 meg guess comes into it.
I nead a defragger. ;)
+--
Given infinite time, 100 monkeys could type out the complete works of Shakespeare.
+-- (Score:-1, Moderator on Power Trip)
The question of how many words a person knows cannot be answered very precisely -- in part because the question is ill-defined. Do you include derived words, or only root words? How well does the person need to know the meaning of the words? What about words that have multiple meanings? Do they count as one word or several?
However, once you settle on a definition of "knowing" a word, you can estimate the number of words a person knows by randomly selecting words from a dictionary of known size (preferably a very large dictionary) and conducting a little vocabulary test. The "known size" requirement of the dictionary isn't trivial, since you are presumably only interested in root words, whereas the publisher's word count will include compound words, whose meaning could be inferred from the root words.
Using the above approach, Nagy and Anderson at U. Illinois, estimated that the average high school grad knows 45,000 words. Throw in all the words that aren't listed in an English language dictionary, such as proper nouns, acronyms, recent slang, etc., and the count will be closer to 60,000. Averaged over the student's lifetime, this works out to learning an average of 10 or more words per day! I've read other, higher, estimates of the size of an adult vocabulary. I found this particular analysis in George A. Miller's The Science of Words.
IANAL (I am not a linguist), and I would be happy to be corrected by someone who is. But as someone who has struggled to learn foreign languages as an adult, I am well aware of how far 5000 words is from a passable adult vocabulary. If anyone else, like me, is interested in learning languages, you might find this web hack I wrote of interest.
So if it's not for the benefit of humanity, why do we all self-destruct within a century or so? Well, evolution is all about compromises. Few of our ancestors lived long enough to die of heart attacks or cancer, since they were more likely to become some predator's lunch. So rather than optimizing for conditions that rarely happen, such old age, nature, like any good hacker, optimized for the common case: youth. Any mutation that increases our survival when we're young at the expense of killing us when were ancient is likely to have been selected for.
In Psychology we were taught that short-term memory usually lasts less than 30 seconds and is limited. Long-term memory is unlimited and is permanant.
A little food for thought. We discussed one patient who had a literal photographic memory. It was explained to us that he committed every memory to long term memory and thus was unable to forget anything. He eventually went insane.
Sorry to bring an unprovable story in but can you imagine the ramifications of that? It would seem that having a selectively photographic memory would be nice. Just remember EVERYTHING that you want--Good times, your wedding or divorce even... I dunno, or an entire textbook before a test. But imagine of you couldn't control what you remembered. Think of all the useless information you recieve every second. What people are wearing, the color of the wall, how many cracks in the wall...
I most certainly would go insane.
-Clump
This is very interesting. Perhaps the variable timing of rod recharge can be interpreted by the brain as improved frame rate. Studies have been done that show the eye jots around what it sees and takes in detail of a small portion of the image. So that initial 200x200 enhanced to 5000x5000 image is then enhanced section by section as the eye focusses on parts in a non-ordered fashion. So if you stand in front of a painting and look at it, your eye is resolving the image more and more accurately the more you look at it. The same thing is true of staring at the head of a pin. First it's blurry, then you focus. Some of that is adjusting focus, some is the gradual resolving of the image.
Back on the topic of human memory, think about all the little details you remember about last weekend. What you did, who you saw. That is the 2-bit per second memory. Now recall everything you know about your favorite song. You know the melody, the lyrics, the beat, effects, maybe the music video, you recall images, times you listened to the song, who you were with. What you recall about a song or a movie or a TV show, or a news article or a web page can fill a lot of data if it is forced into binary. Take the tune of the song. Now first we must describe each note in binary, so assign a number of bits that can describe how well you know each note. 8? 16? Assume the song has a refrain, so part of the song is repeated and hence not new memory. Fur Elise has 17 core notes, making for 204 bits if we differentiate to 12 bit music. Now we know the instruments, how they sound for the song. Describing that in binary can eat up data pretty fast, but we only remember a few samples from the song. My point is that in just a well remembered song we can eat up a meg or more. Know a hundred songs? Well there's a hundred meg. Know your profession? How about movies? A well recalled clip, image, quote, all times the number of movies or shows remembered. We can recall the tone of voice used, the plot summary, and tons more. There is no way this data could be stored in binary form and not take up gigs. Over a lifetime, the 13TB figure seems resonable.
XeoMage