[felix]

Laughter is part of the universal human vocabulary. All members of the human species understand it. Unlike English or French or Swahili, we don’t have to learn to speak it. We’re born with the capacity to laugh.

One of the remarkable things about laughter is that it occurs unconsciously. You don’t decide to do it. While we can consciously inhibit it, we don’t consciously produce laughter. That’s why it’s very hard to laugh on command or to fake laughter. (Don’t take my word for it: Ask a friend to laugh on the spot.)

Laughter provides powerful, uncensored insights into our unconscious. It simply bubbles up from within us in certain situations.

Very little is known about the specific brain mechanisms responsible for laughter. But we do know that laughter is triggered by many sensations and thoughts, and that it activates many parts of the body.

When we laugh, we alter our facial expressions and make sounds. During exuberant laughter, the muscles of the arms, legs and trunk are involved. Laughter also requires modification in our pattern of breathing.

We also know that laughter is a message that we send to other people. We know this because we rarely laugh when we are alone (we laugh to ourselves even less than we talk to ourselves).

Laughter is social and contagious. We laugh at the sound of laughter itself. That’s why the Tickle Me Elmo doll is such a success — it makes us laugh and smile.

The first laughter appears at about 3.5 to 4 months of age, long before we’re able to speak. Laughter, like crying, is a way for a preverbal infant to interact with the mother and other caregivers.

Contrary to folk wisdom, most laughter is not about humor; it is about relationships between people. To find out when and why people laugh, I and several undergraduate research assistants went to local malls and city sidewalks and recorded what happened just before people laughed. Over a 10-year period, we studied over 2,000 cases of naturally occurring laughter.

We found that most laughter does not follow jokes. People laugh after a variety of statements such as “Hey John, where ya been?” “Here comes Mary,” “How did you do on the test?” and “Do you have a rubber band?”. These certainly aren’t jokes.

We don’t decide to laugh at these moments. Our brain makes the decision for us. These curious “ha ha ha’s” are bits of social glue that bond relationships.

Curiously, laughter seldom interrupts the sentence structure of speech. It punctuates speech. We only laugh during pauses when we would cough or breathe.

You may read the technical details in the rest of the article: http://www.msnbc.msn.com/id/3077386/...ience-science/