Evolved Human Behaviors: Nonverbal Communication

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. Examples of play faces in animals are shown below (a dog playing with a human; elephants playing together; a female chimp with a male). In addition, smiling can be traced back to a common ancestor of chimps and humans. See this too!

Play faces

Smiling by a chimp and similarity between chimp and human expressions

• Existence of the trait in physically handicapped children. Play faces are also seen in blind or deaf-blind children. How could they show this expression without ever seeing it unless the trait were innate? Examples of play faces can be seen in a blind infant and deaf-blind 7-year old:

Play faces by a blind infant and deaf-blind child.

• 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 (Figure 2). The eyebrow flash serves as a recognition signal and as an invitation for interaction. Watch an Eyebrow Flash (from the Human Ethology Film Archives). See also a   Himba flash.

Other facial expressions that are seen cross-culturally (many of which are also seen in non-human primates) include expressions of anger and rage (Fig 3), worry or anxiety (Fig 4), and fear faces (Fig 5). An anger face is characterized by the lips tightly drawn across the teeth. Interestingly, there are gender differences in the ability of males and females to read these emotions, with females more capable (more on this is here). With rage, the lips are so tightly drawn over the teeth that the teeth are exposed. Fear faces are characterized by the cheeks tightly drawn back so that side teeth are exposed. The corners of the mouth by be drawn up (almost like a smile), or down).

Coy or flirtatious behavior is also seen across cultures (Fig 6). Typically, the female looks sideways at the male until she catches his attention, Then she turns away and down with a smile, usually while maintaining eye contact. She then turns again toward the male, shows a full smile, but either covers it with her hand or by looking down. These behavior patterns are only seen in females and show up very early in their development. You can watch an example of coy behavior here (from the Human Ethology Film Archives). The intensity of the coy or flirtatious behavior can be intensified with the use of a pout (fig 7). Again, these behaviors are not seen in males. Other examples of female flirtatious behavior is here.

Body language and gestures.
Body language and gestures can also be used for communicating emotional states. These gestures are seen cross-culturally around the world. A few are also seen in non-human primates.

• Arms upraised (Fig 8) signal exuberance or victory.
• Hand chops are used by a speaker to cut through an argument (Fig 9). These gestures are usually timed in cadence with the speaker's voice and with the concepts he/she is trying to make.
• Forcible or power gesture (Fig 10). Closed fists at the end of an extended arm is a forcible or power gesture. It might us used when explaining an idea that destroys or pushes aside all other conflicting ideas.
• The palms-up gesture (Fig 11), is an extension of a begging display (as in begging for food). In this context the speaker is asking for the listener's attention.
• A small thing gesture (Fig 12). The thumb and forefinger are brought together while the other fingers are held away from the hand.
• Precision gesture (Fig 13). The tips of the thumb and forefinger or tips of fingers are slowly brought together to indicate precision. This is used when the speaker is explaining a difficult concept or procedure.  More than one gesture can be be use at the same time. In figure 14 the speaker is pleased with his audience grasping a difficult concept (this speaker is a particle physicist).
• Pushing away an idea or question (Fig 15). The palms are held up and the palms either push away, or push down. This represents pushing away a concept, a question, or holding back the ideas of an audience member.
• Grabbing hold of an idea or concept is shown in figure 16.
• Leaning forward while immobilizing the hands indicates that the speaker is paying attention to you (Fig 17).
• Ideas or concepts are part of one another (Fig 18).
• Finger shake (Fig 19). The finger is shook to keep time with the speakers cadence to emphasize concepts or words. Often the fingers will be raised in sequence to count the ideas.
• Bye/Hi: Figure 20
• Figure 21 is a cultural signal. The gesture changes from one culture to another.

Some video clips of gesticulation are here.

Required Reading on the gestural origins of human language.

Lab instructions are here.