What are the main reasons for prevalence of Imposter Syndrome at selective colleges?
Chance Me threads? 
Or similar breeding grounds for the nattering nabobs of negativism?
A “Lost In Space” reference? Wow, you’re WAY too young.
As far as I can see, it’s because the type of kids who apply to selective colleges tend to idealize these colleges and therefore assume that they are full of super-bright kids who just cruised through high school, easily getting As, getting prizes, etc. They see the accomplishments of the few students who make the headlines for winning top prizes, etc, and assume that these are the average students who attend selective schools.
They do not realize that the majority of kids who attend selective schools are “average” smart kids who work really hard, usually had a good level of parental support, and had a large dollop of good luck.
Moreover, despite the constant talk here about how you need some sort of “hook”, the majority of the 950 students who are in the middle 50% range of students accepted to, say, Princeton, are really no different than 9,000 kids who were rejected. Even many of the 430 who make up the top 25% are only a fraction of the kids with similar profiles who applied. So there may be also a type of “survivor’s guilt”.
Finally, I think that it’s because many parents push their kids by constantly telling them that they aren’t good enough. So, if a kid has been told for 10+ years that they aren’t good enough and they need to work harder if they really want to get into a selective college, they will continue to feel that they aren’t good enough, even if they were accepted.
Ever read up on it? Top performers often doubt their results are more than luck. They see the accomplishments of those better than them or with more striking contributions and judge themselves, downplay their own achievements,- which are often substantial.
Or is it humility?
Imo, the opposite of the overconfidence on Chance threads. Thse kids aren’t close. The concept has been around a long time. One author claimed he could (almost) tell someone was highly accomplished based on this modesty.
Humility doesn’t mean insecurity. Imposter Syndrome is more about insecurity or inability or perception of inability. If you can’t handle college’s academic rigor , humility or arrogance can be minor factors but being academically or intellectually unprepared is likely a bigger factor.
It’s Spiro Agnew via William Safire, although I could imagine Dr.Smith saying it as well. 
You’re still too young…
Many of the kids in selective colleges learned to grow up being perfectionists and highly driven and thus sensitively cognizant of “the bar,” whatever that may be. They tend to constantly measure themselves against others or the conceptual figment of their imagination. In their habitual measuring, therefore, the imposter syndrome is born because they were conditioned to measure themselves against the higher bar and the accompanying feeling of not measuring up to that bar. They’re often highly accomplished kids, yet with surprising poor self-esteem. One can point to all of their accomplishments, the envy of so many, but these accomplishments mean nothing to them, because they’ve been conditioned to always look up, not within.
The imposter syndrome isn’t about those kids who were somehow “lucky” in the admissions. It’s also felt among those in the higher rung. These kids have typically earned admissions to several selective schools, not just one due to randomness of luck.
Is there a co-relation between failing/bad GPA/drop outs/longer time to graduate and Imposter Syndrome or are those two entirely different things.
Does ESL or first generation students have higher chances of this syndrome? Wrong major or track can make one feel stupid as even most genius fish can’t climb a tree.
Athletic, donor or other quota admits with lower academic level than others can feel imposter at academics?
Anecdotal based on the experience of one, but maybe some other “old timers” can back me up. I was pretty confident that I deserved my place at a highly selective college when I attended. At the same time, I did not question whether anyone else deserved to be there. No one I recalled bragged about their HS achievements or test scores to establish their place in the pecking order. I am sure there were some who had less confidence in themselves and definitely people who were cocky vs people who were humble, but that just seemed to be part of a normal distribution of people with different personalities.
With D (highly selective LAC) and S (an HYPS), they seemed to be more aware of the accomplishments of others. Given the increasingly competitive nature of getting into these schools, I think kids are more tempted to brag about themselves to establish their bona fides and place in the pecking order. This then adds fuel to the phenomena that @TiggerDad points to above, which is a shame. It is unhealthy to feel as if your position is undeserved, it is healthy to realize that there is always someone smarter/better than you in just about everything, but that also means there is room for improvement for you.
“Imposter Syndrome” is more than feeling like you can’t keep up. For simplicity, wiki says, “…impostor phenomenon occurs among high achievers who are unable to internalize and accept their success. They often attribute their accomplishments to luck rather than to ability, and fear that others will eventually unmask them as a fraud.” The original info I read dealt with truly successful individuals. Not your ordinary hs val or somesuch who faces competition in college.
But IS has a range, from self-effacing to the crippling doubts.
Nobody wrote that it was about luck, they wrote that it was about the perception of the students that it was luck. So long as kids who they perceive as being as good as themselves are being rejected, they will see that as luck. Besides, there is an element of luck among all “rungs”, because that’s how holistic admissions works. Many kids with SATs and GPAs that match the top 25% of Stanford are rejected by Stanford.
People with impostor syndrome generally think that they achieved what they did either through luck or by subterfuge, and that their luck is going to run out or their “scam” is going to be revealed. a kid in the “upper rungs” doesn’t think that their 4.0 indicates that they are smart, they think that either their high school was easy, or that you don’t really need to be smart in order to get As in high school, and that they somehow managed to “fool” their teachers, but now that they’re in college, where everybody else is “really” smart, they will not be able to fool their professors and they will be shown to be a fake.
But there are many more kids at selective colleges in the “lower rungs”, and they need many fewer mental gymnastics to convince themselves that they do not belong in the selective school that they attend.
PS. I’m skeptical of the claim that social media is to blame for increases in impostor syndrome. First, because there is no evidence that it is increasing, only that people are more willing to admit to it. Second, before social media people only saw perfect families on TV and in movies, and what they saw and heard from their friends, family, and neighbors was just as tidied up and perfectly presented as the lives presented by anybody on FB or Instagram.
LOL. Spiro Agnew. Via William Safire as speechwriter.
Spiro Agnew and William Safire were WAY before my time. FWIW, Dr. Smith’s insults, and there’s a lot of them. Pretty close, no? ?
I’m surrounded by children!!! Get off my lawn!!!
Just as an aside, Lost In Space aired until 1968, two years before Agnew’s speech…
Syndication baby! Aired in the 1970’s and then revived by TBS in 1979.
But will live forever thanks to YouTube.
I think it’s normal to feel some degree of this. My daughter had someone say she was at Amherst because she was “brown”. She could have flexed her first year of straight A’s , but if someone is ignorant enough to make that comment, it’s unlikely they would comprehend the work that went into getting into Amherst College and then continuing to perform so well there.
I honestly think her hearing that comment, didn’t hurt her as much as it helped remind her of all the reasons she is exactly where she is supposed to be.