Cognitive experts classify memories as either short term or long term. A long-term memory could be your first kiss, favorite school teacher, your best friend in high school, or hearing your firstborn child speak for the first time.

Such long-term memories tend to be stable throughout life because they are enhanced by strong emotional feelings attached to them.

Sometimes, the feelings that strengthen these emotional memories can be negative.

For example, many people recall in vivid detail what they were doing and feeling when they learned about the assassination of President John Kennedy or John Lennon.

It’s unlikely that they would recall the same details from just a week before those tragic events because there are not strong feelings attached to the earlier memories.

Even if a long-term memory is not linked to an intense emotion, it is often more stable than a short-term memory that is related to more recent experiences.

For many people, it’s easy to recall the name of the street where they grew up, but it can be more difficult to remember the name of the movie they saw just a week earlier.

One reason long-term memories have greater stability is that they have been reviewed many times over the course of years.

But because we naturally attempt to learn and recall everything that we experience, our brains have to pick and choose what to remember depending on whether or not the information is useful.

For instance, a politician may be better at remembering names and faces because it can aid in his or her political advancement.

By contrast, a mathematician is more likely to remember numbers and equations than names and faces.

Another form of short-term memory that declines with age is working memory, which allows us to temporarily organize and manipulate new information.

When you look up a phone number and remember it just long enough to punch it into your phone, you’re using working memory.

If you don’t make an effort to memorize that number, you probably won’t recall it just five minutes later.