NEW RESEARCH REVEALS INSIGHTS INTO HOW WE PERCEIVE BEAUTY, EMOTIONS FROM A FACE
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NR-11-05 (11/14/05). For more information, please contact Sara Harris at (202) 462-6688 or sharris@sfn.org.
NEW RESEARCH REVEALS INSIGHTS INTO HOW WE PERCEIVE BEAUTY, EMOTIONS FROM A FACE
WASHINGTON, DC, November 14, 2005 — Imagine living in a world filled with a sea of identical faces where you can no longer distinguish one family member from another or your friend from someone you’ve never met. Chaos and confusion would result. So how do we distinguish faces?
New research reveals how the brain gleans and processes information, such as beauty, emotions, even ethnic and group identities, from a face.
An important use of face recognition in humans is mate choice, and a related ability is how we judge beauty from faces. For many years, symmetry was thought to be a crucial factor in distinguishing a beautiful face from an ugly one. New research reveals that bilateral facial symmetry might not play as important a role as previously thought—even faces that have quite different left and right halves can be judged as attractive. “This suggests that you don’t need to have perfect symmetry in your face to be considered beautiful by others,” says the main researcher of the study, Dahlia W. Zaidel, PhD, of the University of California at Los Angeles. “The results also could help clinicians—plastic surgeons and dentists, for example—because they show that perfect left-right symmetry is not critical for facial beauty.”
Zaidel’s study used digitized, head-on, frontal photographs of 56 male and female faces divided into vertical halves on a computer. She then showed the halves to two groups and asked them to rate the half-faces for beauty on a scale of one to five. The participants in the study had seven seconds to view each half-photograph. One group saw only the left halves and another just the right half-faces. A third group viewed the full faces and rated them. On comparing the ratings on each full and half face, Zaidel found similar ratings for half faces and the complete faces. The full faces received a slightly higher rating compared to their incomplete halves, but the higher ratings for full faces Zaidel concludes, is only because it is habitual to make beauty judgments with a full face. “Overall the findings tell us that when it comes to judging good looks, symmetry is insignificant,” says Zaidel.
Although factors within faces which influence beauty judgments remain to be explored, the results make sense in light of the facts about the asymmetry in the functional specialization of our brain hemispheres, Zaidel says. “When we gaze at whole faces, like we do everyday, each face half normally sends separate signals to the left and right hemispheres of our brains, which in turn are not symmetrical in their specialization,” she says. “This could explain why perfect face symmetry is neither crucial nor always present in human faces,” says Zaidel.
The ability to perceive emotion in others’ facial expressions varies considerably across individuals. For instance, some evidence shows that sociopaths are less able to identify fearful expressions than people from the general population. Also, autistic individuals may have general deficits in their ability to detect emotions in faces. It is already known that emotional and cognitive processes in the brain are sensitive to reproductive hormones. New research shows for the first time that the ups and downs of a woman’s natural hormone cycle may affect her ability to judge emotions on other people’s faces.
“Our study finds that women who are not on the birth control pill and are subject to their natural hormonal cycle are more likely to perceive neutral facial expressions as emotional, than women who are on the birth control pill,” says Judith E. Grisel, PhD, of Furman University in South Carolina. The study also finds that women on the pill are quicker to identify happy faces. Therefore, the variations in our emotional perception of faces in our daily interactions may be moderated by hormonal methods of birth control, according to Grisel.
“Our ability to detect emotional expression in others is positively correlated with our internal emotional experience,” says Grisel. “Because women profess differences in their emotional state experience across the menstrual cycle, we hypothesized that they might vary in their ability to perceive facial expressions of emotion as hormonal status varied.”
In order to determine whether variations in sex hormones play a role in modulating perception of facial expressions of emotion, Grisel evaluated women who were either using birth control pills or not, across the menstrual cycle. To do this, she showed her subjects a series of 110 faces depicting happy, sad, fearful, angry, disgusted, surprised, and neutral expressions. Grisel asked her subjects to look at each face, which was displayed on a computer screen for several seconds, and to identify the emotion depicted as well as to assign an intensity score for each face by pressing a computer key corresponding to each emotion they saw. Subjects were also asked to rate the intensity of the expressed emotion.
“There were differences between subjects who were taking birth control and those who were not, as well as differences across the menstrual cycle in those not on the pill,” says Grisel.
Subjects that were not on the pill more often mistook neutral faces as emotional. When ovulating, these women also overestimated the prevalence of neutral faces, and were less able to correctly identify sad faces (in other words, they mistook sad expressions for neutral ones). They also showed a tendency to misidentify sad faces. On the other hand, the women taking the pill were prone to more accurately identify neutral faces. “This is probably because the latter group of women were themselves not as emotionally controlled by their hormonal cycles as the women without the pill,” says Grisel. The study also found that those on the pill reacted faster when they rated the intensity of facial expressions, especially when rating happy faces. This decreased processing time may indicate that they perceive happy faces more readily.
“As far as we know, no one has ever looked at the relationship between perception of facial affect and hormonal status in women,” says Grisel. “These data are important because they demonstrate that the ability to perceive facial expressions varies within individuals according to natural cycles, and that this variation may be moderated by hormonal methods of birth control.”
Emotions based on perceptions of faces extend beyond the individual to groups and complicated group dynamics. In a recent study, a team led by Joan Y. Chiao of Harvard University and Nalini Ambady, PhD, of Tufts University found differences in brain activation in response to emotional expressions on faces belonging to different races.
“The question of how top-down factors such as how one’s racial and social group membership influence basic cognitive and emotional processing is one of the most intriguing and provocative areas of study in social neuroscience,” says Chiao.
The study asked its participants, all White, to categorize fearful, angry, and neutral expressions in White, Black, and Asian faces. “We found that the White participants showed better recognition for emotions expressed in White and Asian faces relative to Black faces,” says Chiao.
The participants better perceived the emotions in White and Asian faces and not in Black faces, (i.e., although Asian and Black faces were both ethnically foreign to the White participants, they reacted to Asian faces more like they reacted to White faces than they did toward Black faces). This difference in perception of emotions on faces of different racial identities corresponded to differences in regional activation of the brain. For example, when reacting to White and Asian faces, the brains of the participants showed activation in the left superior temporal gyrus and right precuneus. These regions were not activated when viewing Black faces. Thus, not only does the study demonstrate that faces of different group identities—in this case Asian versus Black—are read differently, but also that this difference is translated to the activation of very specific areas in the brain.
”These findings demonstrate, for the first time, the neural bases of emotion recognition while perceiving emotions on faces from different groups,” says Chiao. “Moreover, the disparity in neural responses to different out-groups—the Asian versus Black—challenges the notion that the brain has a generalized response to racial out-group faces.”
This study demonstrates for the first time the differential neural responses to faces from different groups. According to Chiao, these results also support the hypothesis that differential activation to faces of different races is likely moderated by degree of racial familiarity.
Next, the researchers would like to examine the neural bases of group based differences in emotion recognition among non-White participants. They would also like to determine whether the neural substrates underlying fear and anger expressions—easily conveyed between same group members—are the same as those underlying other emotional expressions such as happiness, sadness, and disgust.” Such research questions have broader implications for our basic scientific understanding of how the brain recognizes emotions and how cognitive and neural processes are modified by our social experience and environment,” says Chiao.
