"Most online interactions are asynchronous and therefore don’t afford a lot of opportunity for social bonding through laughing."
"Synchronous communication online should lead to more bonding if it allows for laughter."
"You don’t necessarily need humor or jokes to get people to laugh. Normal conversation and interactions will produce more laughter than an intentional use of humor or jokes."
"If you want people to laugh, then laugh yourself. Laughter is contagious."

Weinschenk, S., PH.D. (2011). 100 Things Every Designer Needs to Know About People [Kindle]. pg. 159