If your dominant function is introverted thinking (Ti) then you are an MBTI INTP and a Socionics INTj, that both have the Ti as the most dominant function. If your most dominant function is introverted INtuition (Ni, a dreamer, a non-thinker), then it's the opposite. And if you have extraverted thinking (Te) or extraverted iNtuition (Ne; visual memory) as the most dominant, then you are an Extravert. What makes one an Extravert or an Introvert comes from the most dominant function's direction.