If you want somebody to feel more comfortable with you, like if you want them to calm down or be honest/speak freely, you can subtly mirror their posture/movement.
For example, if they are hunched over, with their hand on their chin, you could lean forward a little and rest your head in your chin. Just in a relaxed way, without making them feel like you are mocking them.
This is used in police interrogations to build report with the suspect, and make them more likely to talk freely and not feel hostility.