Biologically, there is only one quality which distinguishes us from animals: the ability to laugh. In a universe which appears to be utterly empty of humor, we enjoy this supreme luxury. And it is a luxury, for unlike any other social process, laughter does seem to serve a biologically useful purpose. In a divided world, laughter is a unifying force.
First of all, laughter is not the same as humor. Laughter is the physiological response to humor. Laughter consists of two parts -- a set of gestures and the production of a sound. When we laugh, the brain pressures us to conduct both of these activities at the same time. When we laugh energetically, changes occur in many parts of the body, even the arm, leg and trunk muscles.
Philosopher John Morreall believes that the first human laughter may have begun as a gesture of shared relief at the passing of danger.
And since the relaxation that results from a short period of laughter, laughter may indicate trust in one's companions. "Laughter occurs when people are comfortable with one another, when they feel open and free. And the more laughter there is, the more bonding occurs within the group," says Morreall.
We've long known that the ability to laugh is helpful to those coping with major illness and the stress of life's problems. But researchers are now saying laughter can do a lot more -- it can basically bring balance to all the components of the immune system, which helps us fight off diseases. It also reduces levels of certain stress hormones. In doing this, laughter provides a safety valve that shuts off the flow of stress hormones that swing into action when we experience stress, anger or hostility. These stress hormones suppress the immune system, and raise blood pressure.