Anyone who has experienced deep connection through laughing already know this, but it's great that more and more literature is emerging to back the life-experiential findings up. World Science just put out an article on the resonant power of laughter:
Researchers at University College London and Imperial College London have found that positive sounds such as laughter or a triumphant “woo hoo!” trigger a strong response in the listener’s brain...“It seems that it’s absolutely true that ‘laugh and the whole world laughs with you’,” said Sophie Scott of University College London, one of the researchers...The research team played a series of sounds to volunteers while scanning their brains with functional magnetic resonance imaging, a technology that measures brain activity based on blood flow in the brain...Some of the sounds were positive, such as laughter or triumph; others were unpleasant, such as screaming or retching...the response was greater for positive sounds, suggesting that these were more contagious than negative sounds, according to the group...“This response in the brain, automatically priming us to smile or laugh, provides a way of mirroring the behaviour of others, something which helps us interact socially. It could play an important role in building strong bonds between individuals in a group.”