I just graduated with a STEM major. In my experience, there’s nothing that resembles cut-throat competition at Yale. Maybe in some specific pockets of the community, but for the most part, I would say that there’s a lot of comparison that goes on internally (i.e. you’ll probably compare yourself to the amazing people around you, mainly focusing on extracurriculars/research/awards), and you might feel pressure from that. None of it is explicit or verbalized, though. At most, friends who are taking the same classes might try to beat each other’s exam scores, but it’s all in good fun and not actually a serious competition. For the most part, Yale has a very collaborative atmosphere.