Currents of varying intensity produce a wide range of facial responses. The epiglottis half-closing upsets the respiratory system, so that air intake occurs in irregular gasps, rather than calm breathing. Under extreme circumstances, the tear ducts are activated, so that while the mouth is opening and closing and there is a struggle for a sufficient amount of oxygen intake, the face becomes moist and often red. Noises often accompany this odd behavior ranging from controlled snickers, escaped snorts and spontaneous giggles, to ridiculous cackles and noisy hoots. This process that all of us have been through in varying degrees, is the physiological response commonly known as laughter.
Humans have detectors in their brains that are specifically devoted to laughter.
These respond to laughter by triggering other neural circuits in the brain that generate more laughter. This explains why laughter is so contagious. You may think you know your girlfriend inside and out, but she's still a stranger until you've connected with her, body and soul. More Relax With Pleasure Kicking back and relaxing after work is not as hard as you think. Just train your brain and stimulate your senses.