Here is a short clip of Deborah Tannen describing one way boys and girls express themselves differently:
Deborah Tannen, in her 1991 book You Just Don’t Understand: Women and Men in Conversation,* describes how easy it is for a speaker to get the wrong idea about a listener’s behaviour if the listener is of the opposite gender.
Referring to ‘A Cultural Approach to Male-Female Miscommunication’ (PDF), a 1982 paper by anthropologists Daniel Maltz and Ruth Borker, Tannen notes that women are more likely to ask questions and give more listening responses: using ‘little words like mhm, uh-uh, and yeah’ throughout someone else’s conversational turn to provide ‘a running feedback loop’.
Robert Provine’s book Laughter: A Scientific Investigation has a very interesting chapter on contagious laughter. This curious phenomenon has long been exploited in such items as laugh boxes and musical laugh records, as well as being central to laugh tracks (from Ancient Rome to modern TV) and churches of “holy laughter”.
Contagious laughter is, of course, also an everyday occurrence, spreading directly from person to person in normal interaction. But even this activity can become abnormal, when for instance instead of dying down it persists and spreads over a wide area, as happened in the Tanganyika laughter epidemic (though it wasn’t just laughter).