I'm sure one could detect those signals, has to do with body language and the way you carry yourself, the way you talk. We all know people who seem to own the room as soon as they enter and who will make everyone present at least listen - they may not be brilliant, but they have this assurance and way to make people listen, while others seem to excuse themselves a bit if they try to talk to a group of more than three.

I wouldn't get into saying "if you're a bit diffident, then you're most likely a submissive" but maybe a need to have the agreement of others, to please the others before kicking off, is a signal to some that this one's a sub, somehow.