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Human memory is a complex and varied phenomenon, and we could delve into its mysteries every day for a hundred years and still have plenty to talk about. But if I had to pick one factor that was absolutely crucial to the operation of memory, I would pick the deceptively simple concept of similarity. Similarity.

We all think we know what that means. An orange is similar to a mandarin; a zebra is similar to a horse; a cup is similar to a glass; my son is similar to his brother. A car is similar to an elephant.

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Because it holds some personal resonance for me, my recent round-up of genetic news called to mind food allergies. Now food allergies can be tricky beasts to diagnose, and the reason is, they’re interactive. Maybe you can eat a food one day and everything’s fine; another day, you break out in hives. This is not simply a matter of the amount you have eaten, the situation is more complex than that.

Having trouble sleeping is perfectly normal, especially as we age. It’s estimated that half of those older than 55 have trouble getting to sleep or staying asleep.

What to do if your sleep is poor

Let’s start with the easiest situation: you’re not getting enough sleep because you wilfully go to bed too late to achieve your needs.

What mnemonics are, and what they are for

Aids to memory such as acronyms, rhymes, linking information by creating visual images or making up a story, are called mnemonics. Mnemonic strategies have been recommended as appropriate for remembering the following types of information:

I talk a lot about how working memory constrains what we can process and remember, but there’s another side to this — long-term memory acts on working memory. That is, indeed, the best way of ‘improving’ your working memory — by organizing and strengthening your long-term memory codes in such a way that large networks of relevant material are readily accessible.

Oddly enough, one of the best ways of watching the effect of long-term memory on working memory is through perception.

What is neurogenesis?

Neurogenesis — the creation of new brain cells — occurs of course at a great rate in the very young. For a long time, it was not thought to occur in adult brains — once you were grown, it was thought, all you could do was watch your brain cells die!

Adult neurogenesis (the creation of new brain cells in adult brains) was first discovered in 1965, but only recently has it been accepted as a general phenomenon that occurs in many species, including humans (1998).

Elaborative interrogation is a strategy to help you remember meaningful information. The idea behind the strategy is that relevant prior knowledge is not always readily activated when you are trying to learn new information, and sometimes help is needed to make the right connections. The strategy requires you to go beyond the information given to you and to construct reasons for the relationships between bits of information.

To choose a strategy, you must assess the situation. In this case, this may mean an evaluation of a written text. Let's look at how you might evaluate text.

We can classify text at one of three different levels, according to its structure and density₁:

Most mnemonic strategies use visual images. But as I say in The myth of imagery, while there is no doubt that imagery can be an effective tool, there is nothing particularly special about it. 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.

Impaired vision is common in old age and even more so in Alzheimer’s disease, and this results not only from damage in the association areas of the brain but also from problems in lower-level areas. A major factor in whether visual impairment impacts everyday function is contrast sensitivity.