To study under

Hello,

This is a really big paragraph and I'm really sorry for that. Please consider the last sentence. I want to know whether "under" comes back to "potential mentor" or "professors". I, admittedly, don't get the whole idea of the highlighted sentence.

To give an example, every year, thousands of undergraduates apply to the most prestigious PhD programs in the United States. A big part of getting in is having persuasive letters of recommendation that are sent on one’s behalf. These letters have been subjected to the same grade inflation forces running rampant across college campuses. Thus the assessments typically range from “this is a fantastic student” to “this is the most fantastic student.” When I read these letters, what often matters more to me than the content of the letters is who wrote them. When a fellow social or affective neuroscientist writes a glowing letter, it is highly meaningful to me because that person is accountable to me the next time we are at a conference together. In contrast, professors in anthropology can write a glowing letter to me with impunity, regardless of any flaws in the candidate, because I probably don’t know them and they won’t be held accountable. For this very reason, their letters do not hold as much weight with me. The upshot of all this is that a college sophomore thinking about which lab to volunteer for will tangibly benefit from knowing how a potential mentor in the department is viewed by the professors the student might want to study under to get a PhD a few years later. This is complex social cognition.

Reference: Social: Why Our Brains Are Wired to Connect

I would be so much thankful of any help.