Outgoing Personalities Soak Up Joy

The brain of an upbeat, extroverted person responds to a happy human face differently from the way an introvert’s brain responds, a new finding that could help pinpoint how the brain regulates happiness.

Turhan Canli, an assistant professor of psychology at State University of New York, Stony Brook, who did this particular work while at Stanford, used brain imaging to address questions about how the brain, specifically the snippet of tissue called the amygdala, responds when people look at happy faces. The amygdala is also known as the site of fear in the brain, governing “flight or fight” impulses. Earlier research had found that the amygdala is activated when some people look at happy faces, while other research had found that it is not.

The study appears in a recent edition of Science. People with an extroverted outlook on life actually have a robust response of their amygdala when shown a picture of a happy face. The brains of introverts show no such response.

“Extroversion may play a role in how active the brain is in response to stimuli,” Canli said. Fifteen volunteers filled out a personality inventory, testing traits, from tendencies to be optimistic and sociable to anxious, worried and insecure. They then were hooked up to a brain imager. During the scan, they were shown pictures of happy faces. Scans also were taken when they looked at fearful and neutral faces. Personality didn’t influence response to those faces.

Introverts showed no activation of the amygdala when looking at happy faces. Canli takes this to mean that the amygdala registers stimuli that are emotionally or socially important. For introverts, happy faces did not register as socially important enough to activate the tissue. Canli and his colleagues at Stanford suspect that the amygdala’s role in regulating fearful experiences is more uniform, regardless of personality type, because of the deep evolutionary roots of fear response in human survival.