Affect is a psychological term for an observable expression of emotion.
A person's affect is the expression of emotion or feelings displayed to others through facial expressions, hand gestures, voice tone, and other emotional signs such as laughter or tears. Individual affect fluctuates according to emotional state. What is considered a normal range of affect, called the broad affect , varies from culture to culture, and even within a culture. Certain individuals may gesture prolifically while talking, and display dramatic facial expressions in reaction to social situations or other stimuli. Others may show little outward response to social environments or interactions, expressing a narrow range of emotions to the outside world.
People with psychological disorders may display variations in their affect. A restricted or constricted affect describes a mild restriction in the range or intensity of display of feelings. As the reduction in display of emotion becomes more severe, the term blunted affect may be applied. The absence of any exhibition of emotions is described as flat affect where the voice is monotone, the face expressionless, and the body immobile. Labile affect describes emotional instability or dramatic mood swings. When the outward display of emotion is out of context for the situation, such as laughter while describing pain or sadness, the affect is termed "inappropriate."