Humor depends largely on the unexpected, on novelty. This tends to increase levels of the chemical dopamine in the brain. (Fisher, Helen, PhD. Why We Love. p 205. NY: Henry Holt and Company, 2004.
Humor is a diffuse function that engages both hemispheres of the brain. (Carter, Rita, Ed. Mapping the Mind. p 36-38. CA: University of California Press, 1998.)
Humor is the experience of incongruity. Composed of three elements: wit (cognitive experience), mirth (emotional experience), and laughter (physiological experience). You do not need to laugh to experience humor. Less research on humor as compared to laughter. (Sultanoff, Steven, M., PhD. What is Humor?)
The 3WD model of humor, validated by several countries including the United States, involves a stimulus (e.g., joke) and a response (e.g., amused or not amused). Outlines six dimensions of humor appreciation. (Howard, Pierce J., PhD. The Owner’s Manual for the Brain. p 168-170. GA: Bard Press, 1994, 2000.