How we change what others think, feel, believe and do
Chin body language
The chin, as with other corners of the face, has its own body language.
The chin is vulnerable when fists are flying as a good upper-cut punch can knock you out. Even more vulnerable than the chin is the throat, where a predator might try to asphyxiate you or worse. Holding in the chin protects both it and the throat, and hence is a naturally defensive move that people use when they feel threatened.
Holding the chin in also lowers the head, which is a submissive gesture. This is distinct from the defensive move as the head tilts down more and the eyes are often largely downcast. This can similarly be a shy or flirting gesture.
The chin can be used as a subtle pointing device and a small flick of the head may give a small signal that only people in the know are likely to notice.
Jutting out the chin towards a person exposes it and says 'Go on, I dare you, try to hit me and see what happens!' This can thus be a signal of defiance, if not towards the other person then instead towards some situation or person in the conversation.
Men with bigger chins have more testosterone (this has been correlated with those who reach positions of power). Thrusting out the chin enhances this, saying 'I am an alpha male and easily become aggressive'.
Often, when a person is feeling confident, their chin will jut out slightly as they hold their head up and maybe tilted slightly back.
Jutting may also exposes the teeth and is a thus a threat to bite which may be added to an aggressive display.
Pointing at a person with the finger is a threatening act. Doing it briefly with the chin is more covert and can thus be an insult.
Stroking the chin is often a signal that the person is thinking hard. They may well be judging or evaluating something, particularly if the conversation has offered them a choice or decision to make.
The head is a heavy object and is often propped up by holding the chin in a cupped hand, particularly when the person is tired and it may drop. Boredom can make you sleepy and a hand under the chin may be done to stop an embarrassing drop of the head.
Holding the chin also prevents the head from moving and can signal that the person wants to send a head signal but simultaneously does not want to send the signal, for example when they emotionally agree and want to nod, but intellectually want more information so they can have good reason before they say yes.
Beards and moustaches are sometimes controversial items, particularly in cultures where being clean-shaven is the norm. A beard may thus be an indicator of a non-conformist.
A full beard is more likely to indicate a person who has no vanity needs and is confident and relaxed as they are. When the beard is shaped and neatly clipped, it may indicate a more vain and fussy person who is particular about how they appear and what they do.
An unkempt beard that is left to grow wild may indicate an untidy mind or simply that the person is lazy. It may also point to a person for whom external appearance is unimportant, such as a university intellectual.
Stroking a beard can be a preening gesture, symbolically making oneself look beautiful and hence sending 'I'm gorgeous' signals.
When the chin is held level, such that the head is held upright without tilting, then this indicates the person is probably relaxed and unconcerned.
A puckered chin, where it is pulled in appears wrinkled, can be a defensive move of the general form of pulling back. This may be done at the same time as protecting the neck by holding the chin in. It may also be a part of a pouting cluster where the person is feeling hard-done-by or defiant.