A small observational study done by Robert Provine in 2000 showed that humor has little to do with laughter, rather it is our social setting that influences our giggles:

Only 10% to 20% of the laughter episodes we witnessed followed anything joke-like. Even the most humorous of the 1,200 comments that preceded laughter weren’t necessarily howlers: “You don’t have to drink, just buy us drinks!” and “Was that before or after I took my clothes off?.” being two of my favorites. This suggests that the critical stimulus for laughter is another person, not a joke…

However happy we may feel, laughter is a signal we send to others and it virtually disappears when we lack an audience.

Another curious feature of the social nature of laughter is its contagiousness.

In 1962 a small town in what is now Tanzania fell victim to

the “Tanganyika Laughter Epidemic“.

10,000 adult men and women and teens of both sexes caught the “disease” after coming in contact with an infected person.

1963 report,