You honestly take various Myers-Briggs tests and consistently get the result "INTP". That's how I figured it out, anyways.
...your flittering mannerisms fluctuate between giggling uncontrollably and mortified silence.
Well that makes a lot of sense; I'm PMSing.
...?
Shutter Island really freaked you out, because how can you ever be sure you're not delusional?
You know you are a dork, but you find it weird that you are not after high grades, and you are not exactly that math bookworm either. And then you start thinking that you're probably a maverick dork, and keeps on wondering why your Ti works better than everyone else's.
You didn't notice that Spock was supposed to be a parody character until someone mentioned that to you.
You know you're an INTP when you can't give a definitive answer to the question "A group of us are going to xyz this friday, do you want to come?".
My answer to that is nearly always 'Thanks for asking, I'll see how I go' and leave it wide open.
An ISFJ friend of mine used to *always* try to pin down what we would do on a Friday night in advance. Drove me nuts and it took me a while to work out a tactful way to not be locked down by her plans.
They are standing back and observing things without getting into the fray...with either a look of impatience, boredom, or amusement.
When you think that 'concept' is a synonym for 'plan'.
When you agonise over how to precisely word your thoughts on "You know you're an INTP when...".
You are listening to someone pondering, and grasp on to an idea they've given immediately trying to test and strech it.
...you unconsciously (or uncaringly) 'lead others on' with your ambivalence.
...you (sometimes?) reject feelings as ridiculously variable/unpredictable and illogical, and look with distaste at anyone who suffers from such an affliction... luckily you don't have any feelings!
..When someone says something subtle, unimportant, and untrue, and you feel the (nearly) irresistible urge to correct them..
In the midst of something happening to you, you already start reflecting on it in retrospect.
... you can organize your arguments but not your room.
But they're wrong!
FYP. <--Ti editWhen your ambivalence towards the personal defines you.
EDIT: Also when you originally write 'ambivalence to,' but the construction somehow having felt wrong, you Google it and correct the text to 'ambivalence toward,' knowing that had you not done so you could not have lived with yourself.