Laughter, aside from the contraction of 15 facial muscles in response to humor, is so much more than that.
Using laughter as a tool to release emotion and tension is also helpful. Many people under stress watch funny movies or go to comedy bars to be able to laugh the negative tension and stress away. To babies and children, laughter is their way of showing happiness upon discovering something for the first time. According to a detailed laughter study at the University of Maryland, all human laughter consists of varying short vowel-like notes repeated every 210 milliseconds. It may be the ha-ha-ha type or the ho-ho-ho type, but not a mixture of both. An explanation of why laughter is so contagious also appeared in the study. Researchers believe that humans have a detector specifically devoted to laughter and responds by triggering other neural circuits in the brain to generate more laughter.