As Paul Ekman described, it is possible but unlikely for a person in this mood to show a complete anger facial expression. More often just a trace of that angry facial expression may be held over a considerable period: a tightened jaw or tensed lower eyelid, or lip pressed against lip, or brows drawn down and together.[24] Emotions are defined as a complex pattern of changes, including physiological arousal, feelings, cognitive processes, and behavioral reactions, made in response to a situation perceived to be personally significant.[25]