“Do something outside the norms of your own gender and notice the reactions of those around you.” That was one of the first assignments I gave my students when I taught a gender studies course.

Their responses were creative.

One young woman parked in the lot of a local department store, opened the hood, and began looking for “the problem.” She assured each would-be helper that while she appreciated their offers she had it under control.

Most believed her; one a...