The authors of the study, published in Experimental Brain Research, took pictures of 10 men and 10 women from their right and left sides. Then they had 37 volunteers rate how "pleasing" the photos were. The result? The volunteers liked the left-side photos significantly more than the right-side ones.
This was true even when the researchers showed subjects mirror-reversed photos — the subjects still preferred photos of people's actual left cheeks, even if they were flipped to look like the right. And the study authors didn't just take the subjects' word for it. They also measured their pupil size, which can be an indicator of how pleasing someone finds an image. The participants' pupils got bigger when they looked at left-side images, suggesting that they really did like them more.
The authors think this is because the left side of our faces are more emotionally expressive than the right. They cite previous research showing that the right side of the brain does most of the emotion processing. Since it also controls the left side of the face, feelings may be more likely to show up there. And apparently feelings are what we like to see.
While previous studies have shown that people like the left sides of female faces more, the new study reveals that holds true for guys' faces as well. So everyone, take note: if you want to look cute, show off your left side.