According to new research, human eyes may not only be a window of expression, they might be more closely related to the environment than previously believed. Recent discoveries by Adam Anderson, an associate professor at Cornell University, point to the origin of facial reactions as stemming from external stimuli long before they became signals for social communication.
As the development of the species adapted to universal influences for hunter-gatherers, the study supports theories from Charles Darwin in the 19th century concerning emotional evolution.
Anderson, who works at Cornell’s College of Human Ecology, published his findings with co-authors in the March issue of Psychological Science. The paper was entitled “Optical Origins of Opposing Facial Expression Actions” and it details, says Daniel Lee, University of Toronto Ph.D. candidate and lead student author of the study, that the primeval connection between visual performance and emotion was programmed by Mother Nature as an optical principle joining action and reaction to the world around us.
This would have occurred beyond the scope of personal human interaction, and could have been a direct result of early visual encoding. According to the research, the reality that humans perceive is filtered by their emotions before light even touches the inner-eye. In terms of evolution, this became more pronounced because meat-eating predators like humans often develop stereoscopic vision, with both eyes pointed forward, for the purpose of depth perception during hunting.
As neuroscientists try to understand how emotion is communicated to others through facial expression, they follow triggers back to the source and find that the variation of having wide eyes or squinting is directly related to the visual harnessing of light during emotional situations. Anderson and his colleagues at the University of Waterloo and the University of Toronto used optometric measures to discover how light affected the retinas of participants who showed fear and disgust, with neutrality acting as a baseline reading.
Looks of fear brought the eyes wider and allowed more light through a broader visual field, while looks of disgust that led to squinting resulted in less light but better focus and the highest acuity for delineation. The study suggests that facial expressions became a function of survival that maximized how the eyes processed light, but in social situations it was also a window to gauge nonverbal communication, which is far older than the human capacity for language. Both methods of visual processing likely provided an advantage to the evolutionary necessity of reacting to predators, as well as forming strong social bonds with other people in unity against those dangers.
Pupil dilation and constriction trace their origins to primitive functions, which is why a form of squinting takes place both when people are happy and when they are appalled, and therefore the movement of the mouth may have been a social cue for which emotion was being expressed.
Adam Anderson’s work at the Affect and Cognition Laboratory is currently researching how eye movements have added to contrasting reactions across cultures and through history as a way of pinning down proof of the connection. Societies across the globe share the same basic recognition regardless of language barriers, and through nature this likely influenced the way that humanity came to view the world emotionally. In attempts to understand how facial expression and the aperture of the eyes became the window for communication and a way of reading what others were feeling and thinking, the entire species may be granted a deeper connection with the lives of long-lost ancestors.
By Elijah Stephens