Every week, it seems, social scientists find another way in which we divide ourselves into groups. There’s the Generation Gap, the Gender Gap, the Education Gap, people who shop at the Gap and those who don’t, omnivores and vegans, liberals and conservatives, book readers and Kindle readers, rock climbers and normal people, texters and grown-ups, gay and straight, rich and poor, black and white, boxer/briefs and a million other splits. The one that has been bothering me most recently is the gap between the people who read and respond to their email instantly and those who don’t.

“Did you get that thing I sent you about that TV show?” I asked my friend Barbara as we were waiting in line at the Stop and Go Away gas station.

“Oh, I didn’t read my email yet this week,” Barbara said.