Autobiographical memory contains the information you have about yourself. It includes several domains:
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Forget the persistent myth that everything is remembered; that our brains are video cameras whirring away recording everything, and that such 'hidden' knowledge can be brought to light by a hypnotist or alien artefact. Such things are the stuff of fantasy. Of course, there is a nugget of truth there: we can, and do, remember things we've paid no conscious attention to. Sometimes the right question can elicit memories we didn't know we had, in more detail than we imagined we could have. But for the most part, what's not noticed is not remembered. Attention is crucial to memory.
Most people find numbers — phone numbers, personal identification numbers, dates, and so on — more difficult to remember than words. That is, of course, why businesses try to get phone numbers that correspond to some relevant word. The system whereby this is possible — the linking of certain letters to the different digits on a telephone calling pad —is a kind of coding mnemonic. Basically, coding mnemonics are systems that transform numbers into words.
You may have heard of “g”. It’s the closest we’ve come to that elusive attribute known as “intelligence”, but it is in fact a psychometric construct, that is, we surmise its presence from the way in which scores on various cognitive tests positively correlate.
In other words, we don’t really know what it is (hence the fact it is called “g”, rather than something more intelligible), and in fact, it is wrong to think of it as a thing. What it is, is a manifestation of some property or properties of the brain — and we don’t know what these are.
Coding mnemonic
Coding mnemonics are used for encoding numbers. Because words are much easier for most of us to remember, a system that transforms numbers into letters is one of the best ways for remembering numbers — as seen in the modern innovation of encoding phone numbers into letters (0800-ANSETT).
A coding system is very useful for remembering numbers, but it must be said that few people have sufficient need to memorize long numbers to make the initial cost of learning the code acceptable.
Most mnemonic strategies are based on imagery. There is no doubt that imagery can be an effective tool, but there is nothing particularly special about imagery. The advantage of imagery is that it provides an easy way of connecting information that is not otherwise readily connected. However, providing verbal links can be equally effective.
In 2002, a British study scanned the brains of ten "superior memorizers" — eight leading contenders in the World Memory Championships, and two individuals previously studied for their extraordinary memory accomplishments — all people that had demonstrated truly impressive feats of memory, in terms of the ability to quickly memorize hundreds of numbers or unrelated words. The ten "memory champions" were matched with ten controls, who had no memory capabilities out of the ordinary.
The other day I was sitting in the sunshine in my living room going through some journal articles I'd photocopied. I realized I needed to staple the pages together and went down to my study to get the stapler. Approaching my desk, I decided to check my email while I was there. And then, I decided to check my library account online to see whether a book I had requested had turned up. When I'd done that, I went back upstairs to my papers. Where I realized, of course, that I'd forgotten the stapler.
Why do we need sleep?
A lot of theories have been thrown up over the years as to what we need sleep for (to keep us wandering out of our caves and being eaten by sabertooth tigers, is one of the more entertaining possibilities), but noone has yet been able to point to a specific function of the sleep state that would explain why we have it and why we need so much of it.
Subliminal learning achieved notoriety back in 1957, when James Vicary claimed moviegoers could be induced to buy popcorn and Coca-Cola through the use of messages that flashed on the screen too quickly to be seen. The claim was later shown to be false, but though the idea that people can be brainwashed by the use of such techniques has been disproven (there was quite a bit of hysteria about the notion at the time), that doesn’t mean the idea of subliminal learning is crazy.