Laughter: A signal of ceased alarm toward a perceived incongruity between life and stiffness

Main aim of this study is to determine what causes humor, and secondarily, to find out why rhythmic laughter is its expression. In this review, we have analyzed the characteristics of humor and laughter, their effects on health and social behavior, and their correlations with several areas of the brain. Then, we have described the features of laughter, its rhythmic shape and its correlations with other rhythmic human behaviors. We have noticed that the most plausible theory for humor is that of incongruity/resolution, where a) an incongruous event or object provokes a sense of wonder, and b) it is followed by something that reassures the bystanders about its innocuity; but c) not all incongruities provoke humor, but just those that introduce something stiff and stereotyped into a vital and fluid event. What this study adds to what is known, is that not all incongruities produce humor, but only those between a living process and any stereotipy or stiffness we find in it. Laughter is the stigmatization of this unnatural incongruity, through its loud and rhythmic shape, as a sort of signal of ceased alert after the shock induced by what seems hazardous to the fluidity of life.