I don't think there's any relation. Some people may be nervous just because they are interacting with strangers, whereas they would have no problem with people

I don't think there's any relation. Some people may be nervous just because they are interacting with strangers, whereas they would have no problem with people they already know. Personally I don't have nervousness/stress issues in interviews, but I've found that conversation screws up the analytical mode that I use when I'm programming. It's like how people say they don't like having their managers interrupt them in the middle of the day because they get taken "out of the zone." I can program or I can converse, I can't do both without screwing up both of them. That's just my particular conundrum. People probably have all sorts of reasons (besides the possibility of them being bad at programming) for why they may have trouble in interviews.