Scientists have published a study that examines how we perceive beauty and why we are drawn to people with “pretty” faces. They hypothesize that it’s largely caused by biochemical reward circuits in the brain. So is beauty found in the chemicals of the beholder?

The brain is filled with μ-opioid receptors (MOR), which are an essential part of the body’s biochemical reward system. They play a role in human attachment and bonding. Scientists have found in mice that tweaking MOR neurotransmission can have a direct effect on how large their appetite is for sex or food — and also what their preferences are in these areas.

The researchers wanted to target MOR in their study, to find out if our preferences for attractive faces were somehow linked to the same chemicals. If our μ-opioid receptors were stimulated, would we find pretty faces even more beautiful than before?

They began by studying 30 heterosexual males who were told to review female faces on a computer. Everyone received either a dose of a MOR-stimulating drug, a MOR-inhibiting drug, or a placebo. The findings show that men whose MOR was stimulated lingered more on beautiful faces than those who had received a placebo or a drug that inhibited the neurotransmitters. These men also rated pretty faces with higher or more extreme ratings.

Those who received a MOR-inhibiting drug, meanwhile, actually experienced the opposite; the effects of pretty faces were lessened on these males. It appears, at least based on the findings of this casual study, that the levels at which we perceive beauty have a lot to do with the intensity of our neurotransmitters.

On another level, there’s the cliché that attractive people have an “advantage” in many aspects of life — at least on a superficial level — in job interviews, romantic endeavors, political settings. “Facial attractiveness is a powerful cue that affects social communication and motivates sexual behavior,” the study authors wrote. “Attractive people are both judged and treated more positively, reflecting the biased stereotypical notion that ‘beautiful is good.’”

Why do we want to bring attractive people into our lives as friends or sexual partners, into the workplace, or vote them into office? “From an evolutionary point of view, it is important to rate someone as attractive because this indicates health, strength, etc,” Knut Kampe, a researcher at the Institute of Cognitive Neuroscience at University College, London, told the BBC. “Humans, like monkeys and apes, are animals that live in a very complex society. It is very important to know rapidly with whom it might be rewarding to bond. In that way it makes sense to bond with attractive people, irrespective of sex.”

However, being attractive isn’t all just about pretty faces. In a 2001 study completed by Kampe, researchers found that people who rated faces were also in search of qualities like cheerfulness, empathy, and motherliness. “Attractiveness relates to more than just the fairness of the face,” Kampe told the BBC.