One of the great things about MIT is how much info they share about who they are and what they are looking for. This was written a number of years ago, by Chris Peterson, who is still involved with admissions:
On another thread I saw that you were asking how many papers another applicant had published. In case you are thinking that ‘more X wins’, for MIT (aside from Gold at the IPhO / IMO / etc) it doesn’t. They really do choose kids who they think are a good fit for the school, and they turn down lots of exceptionally smart and accomplished students every year.