Short answers, pulled from the story.
Humour is the tendency of experiences to provoke laughter and provide amusement. The term derives from the humoral medicine of the ancient Greeks, who taught that the balance of body fluids called humours controlled human health and emotion. The Latin humor meant body fluid.
The benign-violation theory, endorsed by Peter McGraw, says humour only occurs when something seems wrong, unsettling, or threatening, but simultaneously seems okay, acceptable, or safe. It frames humour as a way to remove the awkward or uneasy feeling of social interactions.
Research proposes two types of humour, adaptive and maladaptive, each with two styles, making four in total. Adaptive humour consists of affiliative and self-enhancing styles, while maladaptive humour consists of aggressive and self-defeating styles. Adaptive styles link to better wellbeing, and maladaptive styles link to higher anxiety and depression.
Western humour theory begins with Plato, who in the Philebus attributed to Socrates the view that the essence of the ridiculous is ignorance in the weak who cannot retaliate when ridiculed. Aristotle later suggested in the Poetics that an ugliness which does not disgust is fundamental to humour.
Women rate humorous men as more desirable for a serious relationship or marriage, but only when those men are also physically attractive. Self-deprecating humour can increase desirability when other variables are favourable, though funny men are also perceived as less intellectual and less honest.
A 1994 study by Karen Zwyer, Barbara Velker, and Willibald Ruch used the cold pressor test and found that participants who watched a humorous video clip showed higher pain thresholds and tolerance afterward. There was no significant difference between the cheerfulness, exhilaration, and humour-production groups.
Confucianist and Neo-Confucian orthodoxy traditionally looked down on humour as subversive or unseemly, though the Analects shows the Master fond of self-deprecation. During the 1930s, Lin Yutang's transliteration youmo caught on as a new term for humour, and forms of humour have flourished again since social liberalisation in the 1980s.