Compressing the lips to make them disappear is a universal trait done to signify stress. The subconscious mind is essentially telling the body to close down and not let anything in. Tightly compressed lips happen honestly and immediately so reflect true stress sentiments to reveal a troubled mind. When the mouth becomes inverted in an upside down “u” shape (down-turned smile) the facial expression turns into a high stress indicator.
Lip pursing is done to indicate thought processing. It usually happens when someone is trying to come up with an alternative idea. Other adjoining cues will tell you whether or not someone is prepared to accept or reject the offer and tell you how best to carry on. Other times, lip pursing is done to show outright disagreement. Usually the eyebrows will frown in unison with pursed lips. Lip pursing is a very reliable indicator of a difference of opinion, and it would be foolish to ignore it. The reverse to lip pursing-judgment is full-lips which indicate contentment. Watching the lips for these quick flashes will tell you a lot about what is going on inside someone’s head. In review, compressed lips show stress, u-shaped mouth shows high stress, pursing shows that a person is considering an alternative, or when accompanied by frowning or additional negative cues, disagreement.