1 We feel superior
According to psychologists, humans tend to laugh if they feel superior to others. When you see a friend falling, for example, you might laugh because you will feel superior to them. In such a case, you feel good because you didn't fall as well.
2 To release tension
You might laugh in serious situations or situations where you aren't supposed to laugh in order to release tension. One of the main reasons people laughter inside elevators is that they don't feel uncomfortable.
3 We got surprised
According to the incongruity theory, humans laugh when incongruity happens between what we expect and what truly happens. The element of surprise and unexpected twists can make us laugh.
4 Laughing is contagious
Accoding to a study, laughter is a contagious thing. This means that you might start to laugh if you see a friend or a relative laughing. This is also one of the reasons why people sometimes laugh during funerals. (See Why do people laugh at funeral?)
5 We laugh when something is violated
According to the Benign Violation Theory, we laugh when something is violated such as values, social norms or morals. The violation must be harmless for a person to laugh. The reason for laughter in such a case could be the release of some the suppressed emotions or thoughts regarding that topic.
6 To release suppressed emotions
In many cases, humans can laugh to release some of their suppressed emotions. Laughing at an adult joke, for example, could help a person release some of their sexual frustration.
7 We are embarrassed
Laughing can be a method a person uses to deal with embarrassment. This is why a person who falls or does a mistake in public might start laughing. (See Why are farts funny?)
8 Because we shouldn't laugh
When a person is in a situation where they shouldn't laugh, they might start laughing. The tension that results from knowing that one should not laugh might force a person to laugh.
9 We have different beliefs
According to psychologists, our beliefs determine whether a joke will make us laugh or not. According to our beliefs, we might find a certain situation funny even if it is not funny to others.
10 Because of different cultures
Culture differences can result in making some things funny for some people and not funny for others. Studies found that certain kinds of jokes appeal to certain kind of people based on their culture and background.