Want to appear more attractive to people? Only show pictures of yourself when you're with your friends. Amazingly, this is not marketing — you don't appear more attractive because you're popular or loved, you actually trick people's brains into considering your face more attractive.
Cheerleaders are a kind of group hypnotism act. Their energy, their choreography, and their uniform appearance meant to take out people's cognitive functions and make them forget that their team is losing. Like armies marching in sync, cheerleaders overwhelm the viewer with an impression of unity and energy that no single member could convey on their own. They also, apparently, overwhelm people with an impression of stunning attractiveness that no single member could convey on her own, but neither armies nor cheerleaders not alone in that. When any people are pictured in groups, each member of the group looks more attractive than they would do on their own. This works for both men and women, and works on both men and women.
If people were to take a guess at why group members appear more attractive than individuals, they might turn up something heartwarming. We are more beautiful when surrounded by the people we love. People pictured with friends attract others because we like people who love and are loved. Unity is beautiful.
While it's true that volunteers for a study rated people more attractive when they were pictured in groups, they also rated people more attractive when they were all in individual pictures, but those pictures were grouped together in one image. A now-famous effect shows that layering people's faces, and taking the average of the however many faces are measured, creates a more attractive face. Average, in the sense of having all irregular features blurred away, is beautiful. The Cheerleader Effect does in time what layered faces do in space. When we look at groups of people we take the image of each face and mentally blur it with the next, making each individual face look more beautiful than it would if we focused on it alone. Groups of people literally fool our brains into thinking of a beautiful whole.