"Stop me if you've heard this before," is what we sometimes say before telling a joke. 

Even if you don't know many jokes yourself, chances are you remember the joke you're being told way before the punchline ... if you've heard it before.

That's because we tend to remember things that make us laugh.

Fact 1: Humor activates the brain's dopamine reward system.

We talked about dopamine in a previous lesson, remember? It was when we were talking about how satisfying curiosity can be comparable to satisfying a food craving. Cognitive studies show that dopamine is important for both goal-oriented motivation and long-term memory.

Because of the rush of dopamine to the brain when we're in on the joke, we are more likely to remember things that make us laugh.

Fact 2: Not any type of humor will do

In a study of 400 college students, researchers found that appropriate use of humor by the teacher resulted in increased retention, while inappropriate, cruel, or unrelated humor did not. Also worth noting is that using disparaging humor targeting students themselves, or even self-disparaging humor, is not a good strategy for boosting retention. Researchers concluded that for improved retention, appropriate, topic-related instructional humor is the most effective.

Fact 3: Humor makes even dry subjects more enjoyable.

In a 2006 study, college students listened to lectures in a Statistics class. One group of students listened to lectured that contained content-related humor, while the other group listened to lectures that contained no humor. Both groups were then tested on the material and completed surveys about how much they enjoyed the lectures. The test and survey results showed that retention was strongest in the lectures with content-related humor and that students reported more enjoyment in the experience.