Facial Expressions

Many facial expressions have been identified as having an innate basis in humans. The evidence for this assertion comes from three lines of evidence:

Comparative ethology with non-human animals.

The human play face is characterized by a loose gape with the upper teeth often shown while the lower teeth are hidden by the lower lips drawn over the teeth. Play faces are often seen when people are rough-housing. It serves as a signal that the play fighting is not real. Play faces are also seen when a dominant individual is playing with a subordinate. Note the play face shown by the young girl playing with the puppies (note also that one of the puppies is smiling). The play face is also seen in a variety of non-human animals and it serves the same function.

Existence of the trait in physically handicapped children.

Play faces are also seen in blind or deaf-blind children.

Cross-cultural studies.

If a behavior is exhibited across all cultures studied, the assumption is that it is innate. One of the first examples of a behavior fitting these characteristics is the eyebrow flash. The eyebrow flash serves as a recognition signal and as an invitation for interaction. Other facial expressions that are seen cross-culturally include expressions of anger and rage, worry or anxiety, and fear faces.