Plenty of research over the past two decades has found beautiful people have a leg up on the rest of us, not only in terms of desirability, but also financially. A new paper points to a specific example of this phenomenon, as well as its surprising source.

A survey of 501 restaurant patrons finds good-looking waiters and waitresses get bigger tips than their average-looking or unattractive counterparts. “I find that attractive servers earn approximately $1,261 more per year in tips than unattractive servers,” economist Matt Parrett writes in the Journal of Economic Psychology.

This inequity is not the result of male customers bestowing financial favors on attractive waitresses. Rather, Parrett reports, “The primary driver (of this dynamic) is female customers tipping attractive females more than unattractive females.”

"Restaurant customers have a taste for attractive servers over unattractive servers and thus, tip them more."

Parrett and an assistant approached customers leaving five Richmond, Virginia-area restaurants on a Thursday, Friday, and Saturday evening. The person who paid the bill used a clipboard to fill out their survey, which asked them to list the size of their bill, the size of their tip, the perceived quality of the service, and the gender and attractiveness of their server.

Analyzing those answers, he found that “Attractive servers earn approximately 1.26 percentage points more on a percentage tip basis than unattractive servers.” That figure went up slightly, to 1.37 percentage points, after taking into account “server productivity and other factors that might affect tips.”

Surprisingly, this “beauty premium” was greater for male than female servers. Even more surprisingly, it is largely the result of decisions made by female customers.

Parrett found no significant difference in the amount male customers tipped attractive vs. unattractive waitresses. But “female customers tip attractive female servers approximately 3.01 percentage points more on a percentage tip basis.”

The results defy some of the basic tenets of evolutionary psychology, which—based on its theories of sexual competition—suggest attractive women would receive bigger tips from men (who are trying to impress them) and smaller ones from women (who might be a bit jealous, or possessive of their apparently enamored mate). Neither proved true in this study.

So what is going on? Parrett notes several possible explanations for his findings, including the fact that beautiful people are often stereotyped as more capable. His results suggest those who fail to meet the resultant expectations miss out on the beauty premium, as “attractive bad servers do not earn more than unattractive bad servers.”

That said, he finds the most likely explanation is that “Restaurant customers have a taste for attractive servers over unattractive servers and thus, tip them more.”

In other words, we simply like being around beautiful people, and the resultant good feelings lead us to be a bit more generous when it’s time to tip.

Findings is a daily column by Pacific Standard staff writer Tom Jacobs, who scours the psychological-research journals to discover new insights into human behavior, ranging from the origins of our political beliefs to the cultivation of creativity.