From the ancient days, makeup has been used to enhance facial appearance in various ways and as part of various rituals. Modern cosmetics focus on making the face look youthful, more symmetrical, and to cover up flaws. This month, we cover an interesting study in the Journal of Cosmetic Science about the illusion effect – which may explain part of the effect that eyeliners, mascaras, and eye shadows have in making the eyes appear larger.
Why Large Eyes?
Eyeliners, mascaras, and eye shadows have been used as an essential part of the makeup toolbox for some time. Some of the positive effects of these products include: Adding depth and dimension, complementing and providing contrast to natural eye color, or drawing more attention to the eyes. One other factor that has been less studied is the illusion effect – designed to make the eyes appear larger than they are. Anecdotally, eyeliners, mascaras, and eye shadows have been thought to have this effect – mostly by makeup artists, but today, we examine a scientific approach at quantifying this hypothesis.
Larger and wider eyes have long been considered to be a sign of attractiveness in women. It is thought that this is due to neoteny1 or the general tendency for men to find women with youthful features such as large eyes attractive. This is hypothesized as being a feature of youth due to the ratio of eye size to the rest of the body. Larger eye size is also a feature along with more familiar features like large lip size and small chin size, a sign of higher estrogen levels. For these reasons, eye size is thought to be an essential feature of attraction for women, and that eye shadows play an important role in creating the illusion of larger eye size. The researchers propose that:
- Eye size is a significant determinant of facial attractiveness. Eye makeup is one of the most effective contributors to female attractiveness.
- Makeup artists have long argued that cosmetics can make the eyes appear larger, but these claims have largely been untested, subjective impressions that have not been investigated scientifically.
- If objective measurements can be confirmed, this can potentially lead to novel makeup techniques or developments of superior eye makeup.
Psychophysics – a branch of vision science and perceptual psychology that quantitatively measures the perceived intensity of stimuli – is used to measure the illusion effect. If the eyes appear larger than they are due to makeup, we could consider this as part of the illusion effect. This experiment uses the staircase method.
Staircase method: 2 faces are presented in each trial – one (say the left side) with makeup, the other (the right side) without. For the subsequent trial, the actual eye sizes (the images of them) are adjusted so that if the observer judges the left image to have larger eyes, the next comparison will have the left image with a small eye size. This is repeated until the observer sees that the left eye is now larger than the right, at which point the slides are adjusted the other way. This method converges on what observers perceive to be “the same” size in appearance regardless of makeup.
The makeup used is composed of eyeliner (surrounds, reshapes, and accentuates the palpebral feature), mascara (elongates, thickens, and darkens eyelashes – thought to make eyes appear larger and brighter), and eye shadow (increases eye prominence), which work together to enhance the eyes. Makeup artists have long claimed that they can make the eye appear larger, but this has not been substantiated in an experiment, and to what degree this illusion effect plays a role has never been measured.
Sample: 22 students 8 male 14 female. All students self-reported having normal visual acuity, color vision, and all participants were unaware of the experiment’s purpose.
Setup and Procedure: Observers were viewing images on a computer at a 70cm distance. Images were composed of Japanese female faces both with makeup (applied by a professional makeup artist) and without. Photographs were edited so that the images have the same face except for the eye area2 using digital photo editing software.
Four levels of eyelash makeup were used: 1 – No makeup, 2 – mascara only on upper eyelash makeup, 3 – mascara on the upper and lower eyelashes, 4 – mascara on the upper and lower eyelashes + false eyelashes applied only on the outer half of the eye.3
Participants are instructed to pay attention to the whole area of the face, not just specific areas, which would better replicate a real-life situation. Finally, whether the control image (the one that was unmanipulated) showed up on the left or right was determined randomly.
Results for Experiment 1:
Both eyelashes and eyeliner were independent factors showing a statistically significant effect, and they also interacted with each other.
- Eyeliner and eyelash makeup induces size illusion; eyes with makeup appear larger than they are
- Interestingly there is no perceived eye size difference between thin eyelashes and thick eyelash makeup.
- The perceived increase is approximately 6% of the original eye size
- Eyeliner affected perceived eye size only when eyelash makeup was not applied, suggesting that the two makeup effects are not additive (at least for the eye size illusion effect)
Sample: 104 female volunteers (mean age 35.1). All reported normal or corrected to normal visual acuity and normal color vision. All participants were unaware of the purpose of the experiment and were tested individually. Eye makeup is being focused on this experiment. Unlike experiment 1, which uses an image of only one individual, this experiment provides more generalizability by adding more models.
Setup and Procedure: Care was also taken to select models whose faces were distinct from each other. We also increased the number of observers to 100 to better reflect public perception. In experiment 2, only female observers were involved as most cosmetics are purchased and used primarily by women. From a marketing perspective, investigating how females perceive faces with makeup is more useful and cost-effective than investigating male perceptions.
A similar setup as experiment 1 was used: 75 cm away from the monitor. Photographs of 6 Japanese females were shown both with and without eye shadow. Multi-colored palette eye shadow composed of five balanced shares, including line color for the edge of eyelids and the primary color for the broader area around the eyes and so on. Comparisons used individual faces that were juxtaposed with each other with and without makeup.
In this setup, half of the participants were instructed to choose which eyes appeared smaller. The other half of the participants were instructed to choose the images where the eyes appear larger.
Results for Experiment 2
Similar to experiment 1, the effects of eye shadow confirmed its illusion effect at a statistically significant degree for all models. However, the eye shadow effect was not equal among the models, suggesting that the eye shadow effect may vary from individual to individual.
- Although individual differences on the model face, the eye shadow illusion made the eye size appear approximately 5% larger.
- The illusory effect of eye shadow is relatively robust
- The eye enlarging effect of eye shadow is likely induced by the synergy between various colors of the eye shadow, not just by its darkest color
- Experiment 1 demonstrated that mascara and false eyelashes make eyes appear larger than they are by about 6% on average.
- When eyeliner is used alone without mascara or false eyelashes, making eyeliner thicker and darker increases the perceived eye size gradually up to 5%. However, the effects of mascara and eyeliner are not additive. If mascara is applied, the eyeliner does not affect perceived eye size. One speculation is that eyeliner and mascara share the same space.
- Experiment 2 demonstrated that eye shadow increases perceived eye size by approximately 5% on average.
- The illusion of eye size enlargement is likely the result of assimilation, similar to the Delboeuf illusion. Eye shadow may make the eyes appear larger because the eyes are either directly assimilated into eye shadow or enhance the assimilation of the eyes into the eyebrows.
- There is likely an upper limit to the illusion effect at around the 5% mark. Many experiments highlighting the Delboeuf Illusion with greater efficiency are highly contrived and unnatural. It’s hypothesized that within the bounds of natural effects (such as the human face), there will be a limit at which point the effect will appear unnatural.
- Illusion effects will likely be a new area of research interest for cosmetics and makeup.
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1Eye size doesn’t change significantly since birth, meaning that babies have relatively larger eye sizes than adults and is thus a trait feature of youth. One can also see exaggerated versions of this in mediums like anime. https://zidbits.com/2011/06/why-do-men-find-women-with-larger-eyes-attractive/
2Each eye area with eye makeup is cut out as an elliptic area with blurred edges, then pasted on the same facial image.
3For more details on experimental conditions, please view: https://pdfs.semanticscholar.org/a6cc/38100e4e5a679d920f2fe427d604557b6237.pdf