Laughter is a communication tool used to share a variety of emotions, including relief, playfulness and joy. When one person laughs and another joins in, bonding occurs, which leads to more laughter and more bonding in a circular pattern.
Although laughing is associated with humor, people laugh in many different situations. Most laughter signals a playful intent and a sense of safety. Appropriate laughter diffuses anger and draws people together in tense situations. In some cases, laughter helps control people. Those in dominant positions laugh more than others, and their subordinates respond by laughing along with them. This helps cement their position in the hierarchy.