Universal faces
For more than a century, scientists have debated whether all humans experience the same basic emotions. The modern version of this inquiry began in the 1960s, when psychologist Paul Ekman traveled to a remote part of Papua New Guinea to study the Fore people, a group with minimal exposure to Western culture. By showing them photographs of facial expressions and asking them to match the faces to stories, Ekman's research showed six universal emotions: happiness, sadness, fear, anger, surprise, and disgust. The Fore were able to correctly identify the emotions on the faces of Westerners, and Americans could just as easily identify the emotions of the Fore.
This research led to the creation of the Facial Action Coding System (FACS) in 1978. This comprehensive system breaks any facial expression into its constituent muscle movements, called Action Units (AUs). For example, a genuine, involuntary smile—sometimes called a Duchenne smile—involves the contraction of the zygomatic major muscle (pulling the lip corners up, or AU12) and the orbicularis oculi muscle (crinkling the eyes, or AU6). The system is purely descriptive, cataloging the mechanics of the face without assigning emotional meaning. It identifies 44 distinct Action Units that can combine in over 7,000 ways to produce the full range of human facial expressions.
Constructed emotions
The theory of universal emotions is not without its challengers. Here in Massachusetts, the work of Lisa Feldman Barrett at Northeastern University's Interdisciplinary Affective Science Laboratory shows a different perspective. Her research is the basis for the theory of constructed emotion, which began to take shape in the early 1990s. This theory proposes that emotions are not innate circuits in the brain. Instead, your brain constructs emotional experiences in the moment.
According to this view, the brain constantly makes predictions based on past experiences and cultural learning. It combines sensory inputs from your body and the world with a conceptual system shaped by your culture and language. An increased heart rate, for example, is a physical sensation. Your brain might construct it as 'fear' when you see a threat, or as 'excitement' at a concert, depending on the context and your learned concepts.
This explains why certain emotional expressions are not universal. Contempt, often characterized by a unilateral lip curl, is one of the most debated. While Ekman later added it to his list of basic emotions, subsequent studies have shown that its recognition is highly dependent on culture. In some studies, the agreement for recognizing contempt was as low as 2% among participants from certain cultures, compared to over 80% for happiness. People in isolated communities who lack a specific concept for "contempt" may not perceive the expression as a distinct emotion at all, seeing it instead as a neutral or confusing gesture.