Imagine being born without the ability to form memories. Nothing you experienced would leave any trace: You would not be able to learn to walk or talk, you would not remember anything that happened to you, you would be permanently imprisoned, like a fly in amber, in the mind of an infant. Our abilities to learn and remember are the foundation stones on which we build our lives; we would be lost without them.

Normally, we learn and remember so effortlessly that we take the skills involved for granted. Consider memory. You have stored information about physical skills such as how to walk and write; you remember your experiences with countless friends and acquaintances, the facts you learned in school about subjects such as history and geography, the meaning of 80,000 English words, and so on. Focusing just on vocabulary, you know how to pronounce and spell each of these 80,000 words, and in many cases you also have a vast store of information about the words. In the case of the word cat, you know what cats look like, how they like to be stroked, their propensity for attracting fleas, and so on. In the course of your life, you have stored an almost unbelievable amount of information, and yet you usually can access information from this store almost instantly when you need it. It is an astonishing feat, and in this book we will be looking at how you do it.