myersandbriggs:

Although the first impression of INTjs is that they are emotionless, when they become inspired during conversation an emotionality previously unseen begins to emerge. Their eyes start flashing with a fanatic light and their passion increases as the conversation progresses. However, they still try to maintain their self-control. INTjs sustain conversations only if they find them interesting. They prefer to keep silent rather than give an opinion on a subject to which they are indifferent.