Are you a social person? Do you avoid speaking to other people? Would you rather be by yourself or with others?
I myself am not very social. If I know the person (or on the rare occasion that we 'click'), then I'm more open and will talk to them. Otherwise...leave me alone, please. Sometimes (like in a classroom), I'm forced into being around people I don't know. Once I'm used to/comfortable around them, I'm more likely to strike up a conversation or make a joke. Other people generally don't try to converse with me, though, which I'm fine with. Whereas, on the internet, I'm relatively social, though still socially awkward. x:
In general, I often prefer to be alone. If I have an opportunity to see friends, I certainly will do it. But if it's a matter of being around family, I sometimes would just rather be alone with my thoughts.