A sense of humor is, simply put, the ability to be amused. Most people have one, and are able to laugh at jokes, humorous situations, and a variety of other potential sources of amusement. In humans, it develops at a very early age, and is often considered to be a vital part of human development. Some animals also appear to find things funny, with the ability to enact jokes and comedies of their own.
Humor appears to be an important part of human survival. The ability to laugh can dispel tension, for example, while an understanding of complex situations can help people to make good decisions. People with a well-developed sense of humor appear to be happier in psychological studies, and some are healthier as well, suggesting that it may just be good for you.
Not everyone has a sense of humor. People with autism, Asperger's syndrome, and a variety of developmental disabilities sometimes lack one, or have a very strange one. For some people, this can be very awkward, as it plays a vital role in human interactions. An autistic, for example, might have a very well-developed personal humor, but an inability to understand why a knock-knock joke is funny. People without one may find themselves belittled, mocked, or treated as stupid, leading to anxiety and depression.
A number of factors influence someone's sense of humor. Age is a big issue. Toddlers, for example, tend to be highly amused by pratfalls and slapstick, while teenagers may delight in irony. As people age and what they find funny develops and matures, they are also influenced by their educational level, the surrounding culture, and their religious faith. Some Christian sects, for example, have a deep appreciation for Bible jokes, while others find Biblical jokes disrespectful and distasteful.
Many people believe that what a person finds funny is something which develops on its own, and that you cannot teach someone to understand why jokes, comments, situations, and events are funny. However, there are certainly things one can do to enhance it. Children, for example, benefit from play and demonstrations of humor, along with encouragements to laugh. While some children's jokes might seem rather inane to adults, encouraging children to tell jokes and to think about what makes things funny, can help them develop a sense of humor.
Older people can also enhance this ability by paying attention to ways in which humor manifests around them. Some people simply have a unique or odd sense of humor which needs a little bit of encouragement to flourish, especially if it is subtle. Asking friends to explain funny situations or jokes after the fact can be informative, as can watching comedy shows and reading jokes, humor columns, and funny novels.