I cannot quote any specific studies. Frankly, I think any study that attempted to establish a correlation between success/failure and a set of characteristics would be faulty simply because there are SO many variables involved and SO many interactions between them.
I will, however, speak from experience...
I had a roomate my Plebe Year who was an absolute geek (he could derive the formulas he needed on the fly), and could handle the physical requirements just fine. You'd think he'd be a shoe-in, right?
WRONG. The stress of doing both at the same time, and doing so while under the other stresses experienced by a Plebe, completely disassembled his other abilitites. He literally fell apart before my eyes; he even REAKED as if he was dying. I'm not kidding, either. I've never smelled anything like that before or since, nor do I wish to. He ended up quitting before Thanksgiving break.
Another roomate, the following year: Total jock, NAPSter, and with the kind of attitude that would see him through anything. Sunk academically. Ended up getting a 4.0 at Georgetown.
Another classmate. Prior enlisted Aviation ET, NAPSter, utter genious (majored in Physics, minored in Russian), 3.9 GPA, could outrun a Kenyan marathon runner. However, he couldn't swim. You could use him as an anchor if you merely tied a rope around his waist and threw him overboard. A total rock. He quit in his third year after they told him he wouldn't be graduating.
Meanwhile, take me. Miserable two first years of high school, highly successful second two years. Moderately successful NAPSter. I hated (and still do) physical exercise, and while fairly smart, I had miserable study habits that never improved. I struggled acaemically and physically at USNA, and came close to having my ticket punched after my second year (1.55 GPA). Yet somehow, I managed to get through. I find it interesting that despite all that, I graduated in the bottom 1/3 of my class, which means a full 200+ classmates of mine had an even harder time.
To be brutally honest, I still walk through USNA and wonder a) how the
&*%$&^% I managed to get through the place, and b) am I now worthy to actually wear the Ring and pass myself off as an Alumni? My Navy career was remarkably unremarkable, and my civilian life afterwards has been, to put it mildly, a shambles. Only now, 16 years after graduating, do I consider that I am finally getting my act together. Hardly what I would expect from a USNA graduate, you know?
I watched classmates get tossed for theft, for academics, for failing PT, for being unable to handle stress, for medical reasons, and because they just plain decided to quit. Some you thought would sail through didn't finish their first semester of Plebe Year, and others (like me) who you'd never thought would make it somehow managed to (and in some cases EXCELLED).
This is why I constantly harp on candidates to take a good hard look in the mirror and and be brutally honest with themselves when they are seeking an appointment, because when it all boils down to the truth, the TRUTH is that the prime factor that determines whether a candidate will graduate or not is the attitude of the candidate. If they want it badly enough, nothing short of being carried out of USNA in an ambulance will stop them.
In my case I swore they'd have to carry me out in a hearse. Fortunately, I never got to test out the veracity of that statement.
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