Some Valentine’s day celebrants prefer to show their feelings with chocolate, roses, and diamonds — but more blunt lovers give gifts to show they mean business: Erotic gifts and sexy lingerie suggest that both giver and taker will be partaking in sweet treats on V-day. If you’re hoping to surprise your partner with naughty gifts on February 14, science suggests you’d better hide your fingers: One bizarre study has shown that, for men, the ratio of your ring to index finger could give your secret away.

In a 2016 study that builds on the Manning hypothesis — which posits that men with ring fingers that are notably longer than index fingers had lower testosterone exposure in the womb — researchers reported that men with less of a difference between their finger lengths are more likely to give sexy gifts, as long as they have high mating confidence.

In other words, the article, which was published in Personality and Individual Differences, says that predicting whether a man is about to give away a nasty treat comes down to two questions. One: Are his ring finger and index finger close in length? Two: Does he think he’s got great game? If the answer to both questions is yes, the study suggests you’re dealing with a serial sexy panty giver.

This strange study is one in a string of articles linking the 2D:4D ratio — that is, the ratio between the second and fourth digits — with supposedly “male” traits. Scientists have argued that small-ratioed men have bigger penises, while others have argued that men with a high ratio have more attractive faces and are nicer to women.

The central idea connecting all of these studies is that the amount of testosterone exposure a male fetus has in the womb determines a lot of his future traits — and the easiest of these to measure is his 2D:4D finger ratio. The hypothesis, which was first proposed by John Manning in 1998, is a controversial one because not all scientists agree that the original study was done very well. Most notably, a study in Evolution and Human Behavior in 2012 provided evidence that the results of Manning’s study were not replicable.

In the sexy lingerie study, however, the researchers assumed that finger ratio is a reliable “proxy of exposure to prenatal testosterone-to-estrogen ratio,” and subsequently found that, among the 130 Caucasian men that participated in their study, those with “highly masculinized” (that is, even-fingered) digit ratios and high confidence in their mating skills were more likely to engage in erotic gift-giving.

Regardless of whether or not the finger length ratio theory is real, confidence, as always, is key, the researchers write. While even-fingered men may have more of a desire to give away lace and leather on Valentine’s day, the researchers point out that “only men with high mating confidence have the courage to act on these desires.”

Photos via Yasmin Tayag