Freud had some strong claims about sexuality, for why some people are straight and others are gay.

弗洛伊德提出了一些偏激的关于性的假说，这些假说解释了异性恋和同性恋的成因。

耶鲁公开课 - 心理学导论课程节选

And most people are heterosexual There's a considerable amount that varies cross-culturally of people who are bisexual But the real puzzle is exclusive homosexuality ? So, why?

多数人都是异性恋的,而且不同文化背景下…,还有很多双性恋者,但真正的难题在于绝对同性恋,为什么呢？

耶鲁公开课 - 心理学导论课程节选