Naked Science Forum
General Science => General Science => Topic started by: neilep on 30/09/2004 20:01:05
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This question was inspired by Deweys Hamster in the 'How Old is your average garden stone ' thread.
How is it that when we know the answer to a question , that it is sometimes difficult to recall the answer, but we know, that we know the answer to the question....Our brain knows it has the knowledge to answer a particular question eh ?..but can't give the ability to express it.....why does this happen ?
Your answers (while you have the ability to give them) would be most appreciated and hopefully...er.....errhm...oh what's the word ?....AHH !!....remembered !!!...thanks
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Well, your brain actually recalls everything that happens to you in life (well, pretty much everything). It stores what you had for dinner every day of your life, what people you met were wearing, etc. However, not all of it can be easily recalled. Strong magnetic fields can be used to stimulate the brain and apparently allows you to remember things. An experiment showed that if you open up the skull and touch parts of the brain using a rod which has a small current passing through it, the person recalls the thoughts stored in small parts of the brain. The memories recalled are extremely detailed and show just how amazing the brain is at storing information.
However, all that information is pretty hard to actually call up by conventional methods...
"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe
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Thanks Qi, that's fascinating, but how does the brain know what it knows, but makes it difficult to actually recall it ?...I'm probably not doing a good job of explainig it but say there's a quiz on tv and you are certain you now the answer but can't vocalise it, but yet you are aware that you know the answer, I think that's weird.
That experiment sounds incredible, perhaps we should all carry around charged rods.....it could almost be the historical meaning for ' jolting ' ones memory !!
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These 'tip of the tongue' moments, as psychologists refer to them, are a common experience.
The brain stores memories and uses the neural equivalent of 'cue-cards' to designate where they are, and how they relate to (cross reference) other topics.
The tip of the tongue experience is like owing a library where the memories are books divided into sections. Losing the index card for a certain book means you don't know where on the shelves it's archived. You know you own the book, and you have a vague idea what it is about, but you cannot remember the precise details of what it says.
You can sometimes solve the tip-of-the-tongue problem by thinking of related memories or situations in which that memory has cropped up. Returning to the library analogy, this works because, by exploring similar memories, you are essentially browsing the same section of the library as the lost book. The 'index cards' for these memories may well cross-reference the memory you've 'lost'. Once you find it again you can write out a new index card, so you don't forget it in future. That's essentially reinforcement and learning.
Think of it like a web, or even the internet. Sites that receive lots of hits (the most memorable because they'll be cropping up most often) will be those with the greatest number of links pointing to them. Even if your forgot the URL for one of these sites you could still find it by navigating via sites you could remember.
A memory with fewer connections / cross-references is much harder to track down and much more susceptible to corruption / decay.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Russ...thanks for recycling this thread.
That's a good point about the brain remembering everything that has ever happened. I was thinking the same thing a few nights ago.......................except very early memories though.
I conducted a poll here some time ago and it seems it's very rare to find someone who can remember before two years old.
It's funny though that when you finally do recollect a distant memory that the memory itself becomes more lucid the more you think about it and eventually you can virtually recall all of it as if it was originally a strong memory....so, as you've concluded it seems the brain does memorise everything....it's just the recollection thatis a struggle.
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From what I've read the current idea is that the brain has two types of memory, one which stores stuff in detail, but you can't access this directly and it's volatile. The other is a sort of semantic network of how all these facts relate to each other chronologically etc. So when you try and recall something it goes through the semantic story part of your memory then this is linked in with the details bit... Whenever the semantic bit tries to grab the details it rearranges everything for better recall i.e. you learn to remember that detail more clearly. So whenever you remember something you actually alter the memory! So although you might have a tonne of stuff packed in to your cranium if you dont try and make sense of it your brain just figures it's not worth indexing, or putting at the top of the HEY REMEMBER THIS hit list. This is how someone who has amnesia still has the details of how to do something but has no idea “how” they know. Similarly how in dreams your brain grabs random junk from your uber memory and makes up a story and time line for it, which tends to end up with fairly bizarre results! This might at first seam like a bit of a limitation, but it prevents people getting hung up on details and remembering stuff they just don’t need to know. If you could recall in exact detail all the bad stuff that happens to you, you just couldn’t get on with life! In the same way that you don’t want to be thinking about the details of a mundane task, if I had to still remember in detail how to type I would end up spending half my life thinking about qwerty layouts, but as it is I’ve “forgotten” about it and just use the logical bit of my brain and memory to sort it all out for me, “I want to type this in quotes please mr brain, kthnx” oh look I didn’t need to over recall or think about typing that [;)].
Knowing something isn't directly linked with being able to express or understand the reasoning... that's what makes your brain so amazing. A child can learn to ride a bike with no concept of what balance or gravity is [:D]. Getting a computer to do something like that is tedious, forgetting stuff is a miracle of biology!
Ask some kid about how they ride a bike and they will say something like "you get on and steer/pedal" [:)] that's all you want or need to know! I imagine the brain is also remembering about the moving horizon and what limb movements were beneficial to not ending up on your ass.
Neil the reason peeps can't remember before around 2 is that the semantic part of the brain that makes sense of all the memories n stuff doesn't develop fully before then. So you can't figure stuff out before then.. Do you remember the details of how you formed sounds with your voice box by gurgling? NO ofcourse not, it's the way the brain gets its basic functionality in! Sort of how you have firmware in computing, some stuff is so low level its just not worth thinking about.
wOw the world spins?
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I knew that already Matt...just wanted to give you an excuse to write an essay ....I know what you Uni peeps are like...you just love to write stuff[:D][;)][:D]
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In the school I'm working at there's one pupil who has some autistic traits. Despite his obvious disability the guy has a calendar memory. For example you can say any date to him and he can recall what day of the week was that. That's actually quite amazing! I've got plenty of other examples as well...
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Our Amazing brains
My son has a fantastic memory. The first time we realized was about 12 years ago when the wife and I took the kids out for a day trip/ picnic.
I can’t remember the name of the place we went too but we ended up at a large country mansion that was run by the national trust. In the gardens there was a very large maze made from large impenetrable privet type hedges .Me being me thought it would be fun to have a go?
Anyway about an hour later and after many dead ends and u turns, and after promising the wife that somehow we would survive the night, my son who was five years old at the time said he knew the way out.
I thought yeah of course you do son but as I had nothing to lose and thought it might remove the tension between me and my wife somehow (Don’t women panic?) I decided to let him have a go at getting us out.
About ten minutes later and without any wrong turns we got out the same way we went in.
What was most amazing was the fact that during our walk through the maze my son had no idea what a maze was and what you had to do when in one. And had taken no notice of which turnings we had taken and what paths were dead ends? In fact he spent most of the time moaning because he was bored.
Somehow he must have subconsciously taken in every turn that we took and then somehow was able to access and recall then memories in order to get us out.
It just goes to show how much information our brains take in without us realizing. There must be gigabytes worth of data going in every minute of the day and yet somehow our brains are able to store it all for future use. [:)]
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I think that forgetting is at least as important as remembering.
If one tries to train a neural network that will remember too much will not learn to generalise.
http://www.faqs.org/faqs/ai-faq/neural-nets/part3/section-3.html
quote:
The critical issue in developing a neural network is generalization: how
well will the network make predictions for cases that are not in the
training set? NNs, like other flexible nonlinear estimation methods such as
kernel regression and smoothing splines, can suffer from either underfitting
or overfitting. A network that is not sufficiently complex can fail to
detect fully the signal in a complicated data set, leading to underfitting.
A network that is too complex may fit the noise, not just the signal,
leading to overfitting. Overfitting is especially dangerous because it can
easily lead to predictions that are far beyond the range of the training
data with many of the common types of NNs. Overfitting can also produce wild
predictions in multilayer perceptrons even with noise-free data.
For an elementary discussion of overfitting, see Smith (1996). For a more
rigorous approach, see the article by Geman, Bienenstock, and Doursat (1992)
on the bias/variance trade-off (it's not really a dilemma). We are talking
about statistical bias here: the difference between the average value of an
estimator and the correct value. Underfitting produces excessive bias in the
outputs, whereas overfitting produces excessive variance. There are
graphical examples of overfitting and underfitting in Sarle (1995, 1999).
The best way to avoid overfitting is to use lots of training data. If you
have at least 30 times as many training cases as there are weights in the
network, you are unlikely to suffer from much overfitting, although you may
get some slight overfitting no matter how large the training set is. For
noise-free data, 5 times as many training cases as weights may be
sufficient. But you can't arbitrarily reduce the number of weights for fear
of underfitting.
Our ability to generalise, and hence to develop generalised models of the universe, must be a consequence of our inability to remember every detail.
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An experiment showed that if you open up the skull and touch parts of the brain using a rod which has a small current passing through it, the person recalls the thoughts stored in small parts of the brain. The memories recalled are extremely detailed and show just how amazing the brain is at storing information.
Who the hell volunteered his/her skull to be opened up?