Last month, I was interviewed by Dr Maria Kempinska, founder of the Jongleurs comedy club circuit, who was awarded an MBE for her contribution to British comedy. She is now a psychotherapist. I talked to her for Your Mind Matters, her series of hour-long chats on the Women’s Radio Station. This is a brief extract of what I said.
… Performing comedy is a bit like performing magic. It’s all to do with misdirection. In magic, you’re looking at the wrong place when, suddenly, something happens somewhere where you are not looking.
In comedy, you have the audience going along a storyline – even if it’s just a short storyline for a gag.
You have the audience going along a storyline for a gag. They’re looking in one direction. They know what’s coming next… they know what’s coming next… they know what’s coming next… and then suddenly, out of left field, from nowhere, comes the punchline… and they react to that in shock.
It’s like a big AAAAARRRRGGGHHHHH!!! But, instead of gasping, they go: “Ahahahahaha!” and laughter is a sort of release of tension. It’s a reaction to something unexpected that happens…
(The full interview is HERE.)
SO IT GOES - John Fleming's blog 
A short and very lucid answer that makes good sense psychologically! Could be expanded into a book, and probably already has, certainly by Sigmund Freud, especially when sexual behaviour is involved, as in the letters of Lord Chesterfield to his son. Cheers, Jaime Smith MD FRCPC