This is a solid read, especially if you're interested in race and race relations.
The needle/Qtip test and the Lord of the Flies-style summer camp for pre-teen boys (aka Stanford Prison Experiment for kids!?) both cracked me up at first, but the results are truly fascinating. I was surprised to learn the extent to which “antagonism can emerge from arbitrary divisions."
For further reading on empathy, I highly recommend James Doty's book “Into the Magic Shop.” I was surprised that Doty’s work didn’t come up in this article because he too is at Stanford. Lots of people studying empathy these days!