In case you want more books and DVDs that are educational and relevant to Laughter Yoga, you may be interested in the following:
Laughter, although ubiquitous and idiosyncratically human, remains a neurologic, social, and evolutionary enigma. There has certainly been no dearth of philosophical speculation concerning its mirthful triggers and metaphysical purposes, but no one has previously actually bothered to accurately describe its essential phenomenology or precise behavioral cues.
So a scientist walks into a shopping mall to watch people laugh. There's no punchline. Laughter is a serious scientific subject, one that researchers are still trying to figure out.
Robert Provine says that homegrown laughter may be what ailing couples need most. Laughter is first and foremost a social signal that binds people together. It synchronizes the brains of speaker and listener so that they are emotionally attuned.