20世纪70年代中期，我和我的同事作了一项试验，我们在街道上随意选择路人，询问他们能否无偿陪同青少年感化中心的少年犯去动物园玩一天。

• In the mid-1970s,my colleagues and I conducted an experiment,we stopped a random sample of passersby on public walkways and asked if they would volunteer to chaperone juvenile detention center inmates on a day trip to the zoo.