Imagine that you are to tell your life story to a new friend, whom you have just met and who therefore does not know anything about your past. It is a friend with whom you are absolutely confident and with whom you can be completely honest. You want to tell him or her about the events from your own personal life that you think are most central to your life story. Which events would you include?

There are probably many candidates, but some events are more likely to spring to mind than others. If you are like most people, you would be unlikely to include, for example, the day you read your first book, when you learned to write your own name, once your wallet was stolen, once you had a toothache and a root canal treatment, or the first time that you went on a plane trip. You would be more likely to tell your new friend about having siblings, beginning school, the first time you fell in love, some major achievement in sports or academics, when you left home, and when you graduated. You might also include your first job, marriage, the birth of your children or grandchildren, and so forth, if you are old enough to have experienced such events.

How are these events selected over others? You may say that they are selected because they are important, much more important than learning to read a book. But then what do we mean by importance here?