A new study has shown that people with symmetrical bodies are judged more attractive by members of the opposite sex, even though the degree of symmetry may be impossible to discern by the naked eye. But researchers say the test subjects were mostly responding to more obvious body characteristics that have been shown to be linked to symmetry; namely broad shoulders and tall stature in men, and small torsos and an “hourglass” shape in women.
Researchers hypothesize that a symmetrical body may indicate a healthy person with an evolutionary advantage. “In animals with two sides that were designed by natural selection to be symmetrical, subtle departures from symmetry may reflect poor development or exposure to environmental or genetic stress,” said study team member William Brown of Brunel University in the U.K. “In many species these departures are related to poor health, lower survival, and fewer offspring” [National Geographic News].
To get exact measurements of test subjects, the researchers used a full-body, three-dimensional scanner, the same sort of device used by fashion designers who want specific details of how their couture drapes the human body. Brown’s team used the device to scan the bodies of 40 male and 37 female college students. A computer gave precise measurements for 24 traits: ankle girth, shoulder width, and others. The computer also created a full-scale, rotating image of each subject’s body [ScienceNOW Daily News]. To prevent bias based on facial features or skin color, the heads of the images were lopped off, and the bodies were given a neutral color.
The researchers then asked other test subjects to rate the attractiveness of people of the opposite sex. Even though the degree of symmetry of the bodies was mostly undetectable, the volunteers consistently rated the symmetrical bodies as more attractive. In the study, published in the journal Proceedings of the National Academy of Sciences [subscription required], researchers say that the more obvious body features could help people determine the fitness of a potential mate faster. “More obvious signals are what animals easily detect and are, thus, conspicuous indicators of developmental quality,” Brown said. “Thus, it is not necessary for animals to perceive these subtle asymmetries” [ABC News]. However, it’s also possible that the obvious features are the primary determinant of attractiveness, and that symmetry is a byproduct of those features.
Image: Lisa Naugle/University of California, Irvine