[Note: this is about humans, not about computers]

I wish I had a perfect memory... What if it is perfect? Why would I consider it not perfect? Hmm.. probably because I can't remember what I want when I want... But does it mean that my memory is bad?

This reminds me of my dad, who every now and then asks me to help him find a lost document. "How is it called?", "I don't know" - his typical answer. After some IT-intuition-based searching, I find a "new document1.doc" in an obscure folder, side by side with "new document1.doc.doc" and tens of other files that have similar names.

I can't blame it on the hard disk, can I? The hard disk has a perfect memory - it can provide the file when I ask for it, bit-by-bit, without a single error. The problem is in knowing where to look, i.e. in knowing the path to the file.

I will attempt to explain how this works with humans, and how our memory can be pretty good, if used correctly.

Follow up:

Memory is not only about storage space, it is about storage mechanisms, and it is also about redundancy.

Some pupils write everything the teacher says, others only write the essence. The former focus on writing, their goal is to keep up with the rhythm of the teacher, not to miss a bit of what is said. The latter category focuses on the content, and transforms the message before writing it down on paper. I am such a type myself, and after spending many years in academia, I can say that my notes are always shorter, and a lot easier to read. The other advantage is that I rarely have to review everything I write in order to 'actually memorize it'; it often happens that before an exam I spend my time doing something other than reading my copy-books.

• Imagine that you have a piece of information - X.
  
• X is a logical consequence of other pieces of information; i.e. you can find X if you put the other pieces together.
  
• Think of it as of a chain of interconnected nodes that have X at its end.
  
• If that chain is the ONLY way to get to X, then if one link in the chain is broken - you'll never find X again.

The original path is the black one. The path is a complete chain, so you can easily get from (a) to X. If you forget something - one of the links is lost; the red X is a broken link between (b) and (c). Once that is broken, you'll never get to X from (a).

The right thing to do is always build more than one path to a memory. If one of the paths is broken, you can use an alternative one to reach the information you were looking for. On the drawing, the alternative paths are marked with green and blue.

How do I do it?

If I have a thought, I play with it in different languages. If I forget the Romanian version, I can recover X by thinking about it in English, or by using my unique notation that uses charts, lines and dots.

Once I do that, I am able to re-build the broken path, and recover the 'lost' information.

Mnemonic chains in action

What is 'biology'?

path#1 - you remember the definition you heard at school: "science about life"
path#2 - in Greek it is Bios+Logos (i.e. life+knowledge)

Even if you forgot some bits of path#1, you can still answer the question (i.e. find X) by taking an alternative path; of course, it only works if you know Greek, or at least its basics.

path#3 - someone with a good photographic memory can remember a book with a nice cover-drawing they liked, or the fact that the biology teacher was pretty :-) so they can think "ah, it's about that pretty lady who talked about evolution of life & co... so it's that type of science about life"

There you go - three different paths to X. This is what redundancy is about - if one of the paths fails, you can use another one. Not only that it will help you find the information you wanted, but it can also help you restore the broken path.

Isn't that a waste of space?

Yes, redundancy comes at a price. I guess most of us see memory as a hard disk, and because of that all of us are familiar with the "low free space" message :-)

Our brain's storage capacity is large enough to handle all the stuff that life throws at us on a daily basis. There is a great mechanism that deals with this problem - forgetting. Forgetting is a feature!

With time you will get rid of the paths that are unused, or that are superseded by other ones. The other paths can be shorter; or they can be longer, but they contain segments that are shared with a lot of other paths (ex: if you follow the logic described earlier, you can figure out what the words "astrology" and "geology" mean, without reading their definitions).

What is the optimal strategy?

• Build as many paths as you can, by expressing a piece of information in other terms
• Don't worry about "wasting space", you will soon forget the paths that are inefficient
• If you speak multiple languages, take the lecture notes in a language other than the one the teacher uses. Not only that this forces you to build another mnemonic chain (one of them is in the original language, the other one is in the foreign one), but this also develops your linguistic skills. And there is another effect - when you translate, you try to optimize the sentence by using a more appropriate vocabulary, hence the resulting text is likely to be shorter.
• The next level is in optimizing the text at the logical layer, rather than at the linguistic layer.
  
  Example: you did a terrific job translating the teacher's speech into English or Russian using your on-the-fly translation skills. You've used shorter words, so you only need one line of text, while your mates need three! That's a 3:1 compression ratio! ;-) But that's not all.

• You can further reduce your workload by expressing the text via a series of flowcharts, hierarchies, arrows, or bubbles. It will take less space, and there's a nice side-effect: you build a couple of additional mnemonic chains. They are:

  • the steps you took to convert text into a diagram (playing with words and symbols in your mind)
  • the graphical representation itself (those with a good visual memory will find it handy)
  • the mechanical work you did in order to draw the chart (those who have a good kinesthetic memory will enjoy this part)

Now that you've associated a thought with multiple things, you've built several mnemonic chains, either of which will bring you to the solution. That's the trick! If you're more into one type of memory (ex: visual, rather than audio) - you'll forget the chains you don't really like, so don't worry about free space.

There's one more thing left to say - forgetting is a feature when it's for an individual, but it's a bug when it's for a race. Don't get carried away ;-)