I've long believed I can tell whether most people are Js or Ps just by watching them interact with me or other people a little bit. I can't identify specific kinds of body language I'm picking up on or explain exactly what I'm referring to, so I'm wondering how many agree that you can get an accurate first impression about it. I can't think of any times that I've later decided a first impression about it was wrong, but of course that could be due to confirmation bias.
The best way I can describe it, though remember it's really just a vague feeling I'm retrospectively interpreting, is that Js seem more reserved in a particular way, regardless of how open, expressive, extroverted and engaged they are. It's as if they're conserving some of their energy or continually re-evaluating the situation, giving the sense that some aspect of their immediate reactions is held back or just overshadowed while other processes are going on. I've only really started wondering how accurate this J-dar thing is since realising that some people analyse those they know quite thoroughly to decide, suggesting they don't have it or don't trust it.
What do you think?