Listen to part of a lecture in a psychology class.

When we think about the past, when we try to remember the past, we remember somethings better than others. Why is that?

Well, there are a few different explanations.

One explanation is that we remember something better if we already have some previous knowledge about it, some previous understanding of it. For example, let's say you are going to go to a classical music concert. If you don't know anything about classical music before you go to the concert, you probably won't remember many details of the concert later on. For example, if somebody asks you about the concert a year later, you probably won't remember what pieces the orchestra played, what order they played them in and so on. On the other hand, if you already know a lot about classical music before you go to the concert, for example, if you've been studying and playing classical music for many years, it's probably going to be much easier for you to recall the details of the concert later on.

Another explanation is that we remember better when there's something unusual ordifferent about what we are trying to remember. For example, let's say you are in aclass at a university, a big class with over a hundred students in it. A year later, which of those a hundred students are you mostly likely to remember? Probably the ones who were unusual or different in some way, maybe a man who was exceptionally tall, or a woman who was exceptionally intelligent. The fact that these students were somehow different from the other students will make them easier to remember.