Men want to buy a nice rock for a pretty face, new research suggests.

Guys are more willing to spring for a bigger, pricier engagement ring when they picture themselves with a more attractive woman than with a less attractive one, according to a new study from Western Oregon University — and women want a larger, more costly ring when they imagine themselves paired with a less attractive man.

And hypothetical partners aside, the greater a woman’s self-assessment of her own attractiveness, the bigger and more expensive her ring choice — “a finding consistent with the notion that desirable women expect greater resource investment from their mates,” the authors wrote.

Also read: The Rules: How to talk to your partner about what to spend on an engagement ring

The study, published in the journal Evolutionary Psychological Science, analyzed data from 590 heterosexual men and women. A majority (64%) of participants, who had an average age of 29, said they were in committed romantic relationships; of the 189 folks who were engaged or married, nearly eight in 10 (79%) had given or received an engagement ring.

The researchers randomly showed participants a headshot of a member of the opposite sex, along with a quick rundown of their hometown, hobbies and traits, and asked them to envision themselves as the person’s boyfriend or girlfriend and rate their attractiveness out of 10. (Photo subjects were pre-rated as unattractive or attractive on a scale of 1 to 10.)

Presented with an array of five identical rings that varied by cost ($500 to $9,000) and carat weight (0.50 to 1.50), men were instructed to imagine they made $36,000 a year and answer the question, “If you decided to propose to this woman after an extended period of dating, which ring would you buy to propose to her?” Women, meanwhile, answered the question, “If this man were to propose to you after an extended period of dating, what is the smallest size engagement ring that you would be satisfied with him giving to you?”

Also read: Stop the insanity over engagement rings. You really can’t afford one.

The finding that men were willing to buy more extravagant rings for a hypothetically more attractive mate “corroborates previous research on mate attraction tactics, showing that men display cues of financial success to attract desirable mates,” the authors wrote. (A 1969 study by sociologist Glen Elder, highlighted by Business Insider, found that attractive women also settled down with higher-status men who were less attractive.) And the revelation that women wanted more lavish rocks from a hypothetically less attractive guy lent indirect support to the idea that greater resource investment (aka more money to spend on them) could compensate for a partner’s lower attractiveness, they added.

The researchers also explored whether age and attractiveness discrepancies in actual couples were correlated with the quality and cost of engagement rings, but found insufficient evidence to support that prediction.

Couples dropped an average of $6,351 on an engagement ring in 2017, according to wedding website The Knot’s survey of 14,000-plus recently married or engaged people — a nearly 25% increase from $5,095 in 2011. Seven in 10 grooms say they landed on a ring budget by themselves, and another seven in 10 brides say they’re aware of how much their fiancé spent. Ninety percent of brides said they were happy with how much their partner plunked down.