PZ Myers made a blog post about a study that looked at the usual reference population for behavioural studies: university students. That leads to unwarranted assumptions about “human nature”.
In Myers words: “No one is denying that there are almost certainly deep commonalities between all members of our species. But there are also phenomena that are much more fluid, and sometimes those phenomena are so deeply ingrained in contemporary culture that we assume that they must be human universals — we assume our personal differences and biases must be shared by all right-thinking, decent human beings. But you can’t know that until you look, and your personal prejudices do not count as data.”