Social anxiety can be defined as nervousness in social situations. Some disorders associated with the social anxiety spectrum include anxiety disorders, mood disorders, autism, eating disorders, and substance use disorders. Individuals higher in social anxiety avert their gazes, show fewer facial expressions, and show difficulty with initiating and maintaining conversation. Trait social anxiety, the stable tendency to experience this nervousness, can be distinguished from state anxiety, the momentary response to a particular social stimulus. Nearly 90% of individuals report feeling a form of social anxiety (i.e., shyness) at some point in their lives. Half of the individuals with any social fears meet criteria for social anxiety disorder. The function of social anxiety is to increase arousal and attention to social interactions, inhibit unwanted social behavior, and motivate preparation for social situations such as performance situations.