How Did Emotional Facial Expressions Evolve?
Christopher Philip
Research by Cornell neuroscientist Adam Anderson suggest that human facial expressions arose, not from or for a communicative purpose, but rather as an adaptive reactions to environmental stimuli.
Anderson, an associate professor of human development in Cornell’s College of Human Ecology and co-author says in video that the idea for the study came about because he wondered about whether human facial expressions had another origin besides their purpose as an emotional communication device.
Perhaps emotional expressions evolved not to communicate emotion but to “change the way the person perceives the environment.”
The study began first by testing the acuity and sensitivity of the eye in a relaxed facial expression. Then they looked at fear expressions to see if it would enhance the sensitivity of the eye.
We know that narrowing the eye produces the emotion disgust whereas in fear, the eye is widened.
They found, however, that the expression of fear which widens the eye also enhances the ability of the eye particularly in low light levels.
In contrast, when people make the disgust expression, which narrow the eye, it tends to impairing sensitivity of the eye, but at the same time enhances the eye’s ability to see on a finer scale; the acuity of vision.
So, he says, it’s not just about the opening and closing of the eye, but rather how the center of the eye, the fovia becomes more sensitive to visual information.
Fear and disgust had opposing effects on how the visual system operates.
The research implies that facial emotions began to improve vision. When we’re scared, our eyes widen permitting us to take in more information quickly whereas in disgust, our eye closes to reduce light hitting the eye and therefore rejecting negative or disgusting stimulus.
Anderson says that we tend to think that perception is rooted in reality, but rather emotions at the very first stage are shaping what we tend to perceive. In this way, our emotions and our eyes are actually doing a fair amount of filtering.
Image Credit: Shane Gorski
Resources
Susskind, Joshua M and Adam K Anderson. Facial Expression Form and Function. Communicative Integrative Biology. 2008. 1(2): 148–149. PMCID: PMC2686004
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2686004/