One who has a stiff upper lip displays fortitude in the face of adversity, or exercises great self-restraint in the expression of emotion. The phrase is most commonly heard as part of the idiom "keep a stiff upper lip", and has traditionally been used to describe an attribute of British people, who are sometimes perceived by other cultures as being unemotional. A sign of weakness is trembling of the upper lip, hence the saying keep a stiff upper lip. When a person's upper lip begins to tremble, it is one of the first signs that the person is scared or shaken by experiencing deep emotion.