Root: Don't have any theories. I don't know. Don't know why. Kept to himself.... The only thing I could even imagine is that he talks in his biographies about being, you know, his identity crisis, his "am I black or am I white?" He chose black. And he hung out with a couple of black kids and never went near anybody and his wife? That's the only thing I can think of. All my buddies are white, what can I tell you! They don't know him, nobody's ever seen him, I don't know what to tell you.
In his memoir and in interviews, Obama has said he got serious and buckled down in New York. "I didn't socialize that much. I was like a monk," he said in a 2005 Columbia alumni magazine interview. He told biographer David Mendell: "For about two years there, I was just painfully alone and really not focused on anything, except maybe thinking a lot."
The question remains, wouldn't those in the same major/minor have taken classes with him? I believe the number I've seen was 400 poli sci majors in 1983.