Generally speaking, I am more uncomfortable around those of the same gender, just as I'm more likely to be uncomfortable around those of my same age group. I think the more "different" someone is, the less likely I am to feel judged. Possibly even different cultures, a few of my Chinese classmates in college kind of took to me for some reason. There are exceptions of course, individual personalities vary, and I'm never really comfortable around anyone, it's just more uncomfortable when it's same gender and/or same age. And authority figures of any kind intimidate the crap out of me.