facial expression
a form of nonverbal signaling using the movement of facial muscles. An integral part of communication, facial expression also reflects an individual’s emotional state. Charles Darwin suggested that facial expressions are innate reactions that possess specific survival value; for example, a baby’s smile evokes nurturing responses in parents. Although controversial, this theory has been supported by cross-cultural research, which indicates that certain facial expressions are spontaneous and universally correlated with such primary emotions as surprise, fear, anger, sadness, and happiness. Display rules, however, can modify or even inhibit these expressions, as can physical conditions such as parkinsonism, which produces an expressionless, masklike countenance.