In a study published in the medical journal Plastic and Reconstructive Surgery recently (and profiled in this May 28 New York Times article), Yale University researchers examined how features of the eye and eyebrow affect our facial expressions and, in turn, how other people use this information to guess our mood at the time.

Study participants were shown 16 digitally altered versions of the same face, each with different eyebrow placement, lid shape, and level of wrinkling. For each photograph, they were asked to rank on a scale of one to five the presence of tiredness, happiness, surprise, anger, sadness, disgust and fear.

The results might surprise you:

“…many of the pictures that mimicked various plastic surgery procedures, such as eyelid surgery or brow lifts, actually generated worse scores, with study participants rating those faces as looking angry or tired.

For instance, drooping of the upper eyelid was the biggest indicator of tiredness, but a picture that simulated a type of eyelid surgery — involving the removal of excess skin from the upper eyelid — made the woman look even more tired and sad, the study participants reported. Raising the upper eyelids produced an increase in the perception of surprise and fear.

“A significant number of plastic surgery patients opt for eyelid surgery, forehead lifts and face-lifts not only for rejuvenative reasons, but to change an unattractive facial expression as well,” said Dr. John A. Persing, one of the study authors. “Our findings indicate that moderation is best when removing excess skin in the upper eyelid. You do not want to create an overdone look that actually makes you look more tired.”

It’s about time researchers conducted a study like this, and I’m impressed with the ethics at play here: plastic surgeons telling people to scale back on plastic surgery? Yet another good reason to save your money and avoid going under the knife, if you ask me.

If the extra money in your pocket isn’t enough to make you smile, though, remember – photographs with crow’s feet added around the eyes were ranked as particularly happy. So swallow any self-consciousness and smile wide!