A bubble of perception gets trapped, somehow, and that bubble is what we call judgment.
Judgment after all is never judgment of the thing itself but some determination based on perception of the thing itself. So in some sense it's tautological to say judgment is perception brought to a halt. But what makes the stillness?
Personally I think of introversion and extroversion by themselves as impersonal, mostly unstoppable directions of attention. By existing together they create a potential third kind of attention, and perhaps we can call it consciousness, or the beginnings of consciousness, where the external and the internal are addressed from the point of view of the other. And the beginnings of judgments in general occur at those points where one instance of a drive to attend in one direction is halted or compensated for by one instance of a drive to attend in the other direction. It's a survival mechanism of sorts, probably non-conscious but vital to our existence. If there were no such check in drive, the third position would disappear.
So, that's judgment?