Scientists disagree about the number of facial expressions that humans can make. Some state that all human facial expressions are variations of four basic faces that people make, whereas other scientists suggest that 21 or more facial expressions are possible. Facial expressions are important for communication between people.
Scientists who study facial expressions have largely concentrated on six different basic emotions: fear, sadness, happiness, surprise, anger and disgust. Each of these basic emotions activates a group of similar muscle movements that give each expression their characteristic look. When surprised, for example, people widen their eyes, open their mouths and raise or lower their eyebrows, depending on whether they are happy or sad about the surprise.
While these six expressions are rather different from each other, facial expressions vary in more subtle ways to help convey emotions that are more complex. For example, the emotions “appalled,” “hatred” and “furious” are all derived from the “anger” basic group, but they have subtle differences that allow people to discern the emotions of others. Scientists have begun using computers to help study facial expressions. In doing so, they have identified common characteristics of related facial expressions. The computers have confirmed that facial expressions exhibit common traits that identify the base emotion.