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See Inside November / December 2010

Why do we use facial expressions to convey emotions?

How do we “see” with our eyes closed when we are dreaming?
—Robert J. Evans, via e-mail

Robert O. Duncan, a behavioral scientist at York College, the City University of New York, explains:

AS YOU SUGGESTED by the phrasing of your question, people don’t actually see in their dreams. Sight depends on light entering the eye and stimulating the retina—something that doesn’t happen when we are lying in the dark with our eyes shut. Nevertheless,
studies that compare the vivid imagery of dreams with daytime vision reveal similar patterns of activity in the visual cortex, the largest brain area devoted to vision.

That is why some researchers believe dream visions come from visual centers in the brain. In the mid-1970s dream researcher J. Allan Hobson and his colleagues at Harvard Medical School proposed that the brain spontaneously generates electrical pulses while dreaming. These signals, known as PGO waves, originate in the visual cortex and in two
other visual regions of the brain: the pons and the lateral geniculate nucleus.

PGO waves are most prominent during rapid eye movement (REM) sleep, the part of sleep when most dreaming occurs. The spontaneous activity from PGO waves may start in the visual areas of the brain but ultimately creates a cascade of activity that taps into the brain regions that house memories.

But not all investigators agree that dream imagery originates in visual areas. Several dream researchers have proposed the opposite path, suggesting that dreams originate in the regions that store memories and then connect to visual brain areas. This theory would explain why dream images are only as detailed as our memories.

For instance, let’s say you are thinking of your grandmother. Your memory of her might not include the mole she has on the right side of her face, something you would clearly see if you were sitting next to her. The lack of detail that is characteristic of memory occurs also in dream visions.

Why do we use facial expressions to convey emotions?

Mark A. W. Andrews, director and professor of physiology at Lake Erie College of Osteopathic Medicine at Seton Hill University in Greensburg, Pa., replies:

JUST AS A PICTURE is worth a thousand words, our faces can express a wealth of information. The ability to communicate subtle emotions with a simple raised eyebrow or curl of the lip may be innate. Charles Darwin was one of the first to propose this theory in his book The Expression of the Emotions in Man and Animals, published in 1871, in which he wrote: “The young and the old of widely different races, both with man and animals, express the same state of mind by the same movements.”

Recent work supports Darwin’s theory that smiles, grimaces and more nuanced expressions are hardwired—an artifact of living in social groups. For example, studies show that infants, including those who are blind or have underdeveloped brains, use facial cues to tell their parents how they feel. Infants communicate with their faces even before they are old enough to understand the meaning of their own expressions. Because humans depend on one another for survival, we must communicate; facial expressions may have evolved as efficient ways to telegraph feelings and intentions.

Although using facial expressions to convey emotions may be largely instinctive, there is also a learned component. Japanese women and men, for instance, are taught to mask overt displays of emotion in favor of a socially acceptable smile.

By studying faces, researchers have matched subtle changes in the positioning of the mouth, eyes and eyebrows to variations in six basic human emotions—happiness, surprise, disgust, sadness, anger and fear. Scientists are using this information to develop computer technology that analyzes facial movements and tics to help assess the veracity of suspects’ testimony.

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