I noticed this in primary school, when we were streamed to different classes and my new classmates would be chattering away and monkeying around while I stayed quiet unless spoken to. 20 years later, this personality trait/ habit remains unchanged. It is more clearly defined now though, in that the personal SOP in groups where the ratio of new (relatively or otherwise) people to people I am familiar with is imbalanced is to not contribute to conversation unless posed a question or an invitation similar. Now if you were oddly interested in complimenting me, you might offer a few alternatives to the term 'anti-social' and say maybe I'm more of an observer or listener, but the truth is, after the hellos and intros and where-are-you-froms, I'd have gone back to talking to myself if there's nothing interesting going on. That might sound snobby and perhaps it is, but it's something I don't seem to have been able to fix so far, and I definitely do not like it! It's not that I feel superior or more interest-worthy than anyone, it's just that there's more comfort in picking up where I left off in my mind before this disaster started. And I probably am waiting to leave after a decent amount of time has passed, so as to avoid seeming even more impolite than I am sure to have come across. Itching to get away from the awkwardness so that I can stop feeling guilty about creating it.
After secondary school, I got a mobile phone which introduced other ways of keeping to myself, which, come to think of it, probably come off looking even more rude!
Guess it's just a part of me I'll never particularly love, but also will not find significant enough to change. Perhaps cos I'm comfy with one-to-ones. Hmmm.
There are occasions in new groups where I feel comfy and am a cartwheeling bag of fun filled with questions, laughter, light sarcasm and sunshine, tho! Sadly, this is super rare. Most of the time, sunshine says 'nope, no cartwheels today!' and so I start drooping, left alone with inward sighs.
Thank god this behaviour happens exclusively around people I'm not very familiar with. I've exactly one truckload of cartwheel buddies, and I'm glad I don't feel awkward around them, cos we make a fantastic bowl of fruit loops and sliced banana.
You know, I should really attempt an actual, physical cartwheel one of these days.