I think the answer is that both play a role but some of the effects are due to stereotypes above and beyond in-group favoritism.

我想两者都有,但刻板印象的影响,要高于组内偏爱。

耶鲁公开课 - 心理学导论课程节选

So, cognitive dissonance motivates me to create an answer that's more comfortable for me, "This must be a really wonderful group with a wonderful bunch of people."

所以认知失调促使我想出另一个答案,让我可以接受的答案，“这一定是一个很棒的兄弟会，里面的人都很棒”

耶鲁公开课 - 心理学导论课程节选