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Skin Tone Influences Perception Of Beauty, Health, Age, Sociobiologists Find

Using a revolutionary imaging process, a new study is revealing that wrinkles aren't the only cue the human eye looks for to evaluate age. Scientists at the Ludwig-Boltzmann-Institute for Urban Ethology (Austria) and the Department for Sociobiology/Anthropology at the University of Goettingen (Germany), have shown that facial skin color distribution, or tone, can add, or subtract, as much as 20 years to your age. The study was presented at the Human Behavior and Evolution Society (HBES) annual meeting, June 7-11, 2006, in Philadelphia, PA. The study used 3-D imaging and morphing software technologies to remove wrinkles and bone structure from the equation to determine the true impact of facial skin color distribution on the perception of a woman's age, health and attractiveness and is currently in the edit acceptance process with the journal Evolution and Human Behavior.

"Until now, skin's overall homogeneity and color saturation received little attention among behavioral scientists. This study helps us better understand that wrinkles are not the only age cue. Skin tone and luminosity may be a major signal for mate selection and attractiveness, as well as perceived age," says lead researcher Dr. Karl Grammer, Founder and Scientific Director of the Ludwig-Boltzmann-Institute for Urban Ethology, University of Vienna, Austria.

Taking digital photos of 169 Caucasian women aged 10-70, the researchers used specialized morphing software to "drape" each subject's facial skin over a standardized bone structure. Other potential age-defining features such as facial furrows, lines and wrinkles were removed. The subjects who were judged to have the most even skin tone also received significantly higher ratings for attractiveness and health, and were judged to be younger in age.

Tone variances can be caused by several factors including cumulative UV damage (freckles, moles, age spots) natural aging (yellowing, dullness) and skin vascularization (redness). Not surprisingly, the study hinted at a positive correlation between the amount of accumulated photodamage and the amount of uneven skin tone.

"Whether a woman is 17 or 70, the contrast of skin tone plays a significant role in the way her age, beauty and health is perceived," says study co-author Dr. Bernhard Fink, Senior Scientist in the Department for Sociobiology/Anthropology at the University of Goettingen, Germany. "Skin tone homogeneity can give visual clues about a person's health and reproductive capability, so an even skin tone is considered most desirable. In this study, we found cumulative UV damage influences skin tone dramatically, giving women yet another reason to prevent UV-related skin damage or try to correct past damage that is causing uneven skin tone."

About the Study

Drs. Karl Grammer and Bernhard Fink conducted the study at the Ludwig-Boltzmann-Institute for Urban Ethology, in Vienna, Austria, and the Department for Sociobiology/Anthropology, in Goettingen, Germany, with funding from P&G Beauty, a division of The Procter & Gamble Company. The study design employed high-resolution digital images, taken under cross-polarized lighting conditions, obtained from 169 female subjects aged 10-70 years. These women were imaged from three angles: frontal, left and right profile. Their potential age-defining features such as facial furrows, folds, lines and wrinkles at the mouth, nose and eye area were then digitally removed. The resulting images were then transposed to a standard 2-D template that was then fitted to a standardized virtual 3-D skull where confounding variables such as overall face shape, lighting, camera angle, eye color/form and hairstyle were eliminated, leaving composite skin pigmentation (tone) as the only variable.

These 169 standardized "stimuli" faces with skin color distribution as the only variable were then blind-rated by 430 participants (incomplete design such that each rater judged 10 randomized stimuli). Raters were asked to estimate the age of stimuli faces as well as answer questions relating to general attractiveness, health and skin attributes.

Next Phase of Tone Research - Getting Under the Skin

As a next step, Drs. Grammer and Fink will partner with P&G Beauty scientist and skin imaging expert, Dr. Paul Matts to look at the distribution of light reflecting molecules - called chromophores - in study subject's skin and correlate them with perceived attractiveness. A non-invasive imaging technology called the SIAscope - originally developed for early skin cancer detection - will help the scientists get under the skin's surface to study the chromophores. Chromophores directly affect how the human eye perceives qualities such as luminosity in young skin or dullness in aging skin.

The researchers already know from the previous tone study that the uneven distribution of one chromophore - melanin - is related to cumulative UV damage, and seems to increase perceived age. By using the SIAscope to measure melanin and the two other chromophores of collagen and hemoglobin, researchers can begin to map out these substances - all which change with age - to determine the optimal distribution that the human eye tends to find most pleasing.

"Because skin has optical depth, our eyes perceive discolorations on the surface and in underlying layers. This discoloration can be subtle or overt. We believe the judgment of facial skin age is influenced by the frequency of lines and wrinkles, but also by uneven chromophore distribution and a decrease in light reflection," says Grammer.