"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.
About Ludwig-Boltzmann-Institute for Urban Ethology
The Ludwig-Boltzmann-Institute for Urban Ethology was founded in 1972. It is a division of the Ludwig Boltzmann Society for the promotion of the sciences, a semi-public non-profit institution for the promotion of the sciences in Austria. The institute works on a multidisciplinary basis. The scientific staff consists of medical doctors, psychologists and sociologists. It is financed by a subsidy from the Ludwig-Boltzmann-Society, the Austrian Federal Ministry of Work, Health and Social Affairs and through contracts for research projects. The Ludwig-Boltzmann-Institute is one of 129 research institutes belonging to the Ludwig-Boltzmann Society.
About the University of Goettingen, Department of Sociobiology/Anthropology
The Department of Sociobiology/Anthropology at the University of Goettingen devotes its research to the scientific study of behavior in humans and primates. The scientific staff consists of anthropologists, ethologists, behavioral ecologists, and geneticists, and research involving humans focuses on the study of physical attraction and the hormonal basis of behavior. The department's activities are mainly funded by the University of Goettingen and the German Volkswagen Foundation.
About P&G Beauty
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