So, last week we were at the Microsoft Research confab on social computing, where Liz, Clay, Joi, me and a couple of others formed a back-back-channel IRC chat, about which Liz writes insightfully. Steve Johnson was at the conference and didn't join in. But, humbly, neither did he tell us that he talks about backchannels in his mind-opening book, Mind Wide Open. I just got up to that chapter in the book. Steve is arguing that laughter is more about forming social bonds than about finding jokes funny. (When I read what Steve writes, I feel tumblers clicking into place. Click click click, he's unlocked another idea.) Then he writes about his experience at a conference where the backchannel was projected onto the screen, points something I haven't seen observed before, and relates it to brain chemistry:

...the most interesting side effect of this discussion was that the arrangement sucked all the jokes out of the room and into the chat....You'd see people smile to themselves as the joke scrolled across the screen, but they wouldn't laugh out loud...If laughter is primarily a form of social bonding, then depriving the room of laughter will have a dramatic effect on its general tone....[W]ith the humor stashed away on digital screens, our brains had been deprived of the reward chemicals triggered by laughter. Jokes on their own simply weren't enough. [pp. 128-9]

I've already bought Mind Wide Open for two relatives, and I expect I'll be buying some more. Steve writes beautifully at every level, from graceful sentences to a structure that moves you along like a good song. Plus, every three pages there's an insight that rewires your brain. This is a damn fine book.