They often look the same.

You make a bit of effort to make conversation with someone you don't know: they give the minimum responses, move away when they can do so, and don't reciprocate initiation.

This could be shyness or arrogance. Very tough to tell the difference. Plus the two can actually be connected: if you see yourself as very different from others, the natural instinct is a mixture of insecurity ('I don't fit!') with arrogance ('I see things these guys don't'). I think the main way not to end up with a mix of both is just if one is very strong: if you're too insecure to be arrogant or too arrogant to be insecure.

This surprised me as well when I first heard it, but it's apparently a really common problem for shy people. I tend to shy back and do my own thing, and apparently some people took that as meaning I felt like I was too good to talk to them.

Now that I've trained myself to be more arrogant, it's become much less of an issue.