16 Dec 2018

Fingers, genes, infidelity and tabloid science

Mashing together the results of two separate studies, several papers claimed that women with an index finger longer than their ring finger are “cheaters”.

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In another attempt to make sensational news out of a scientific study, some Russian and Ukrainian media reported that you can recognize “promiscuous” or “unfaithful” women by the length of their fingers. The claims exaggerate the findings of two different studies conducted in 2015 and 2018, both published in “Biology Letters” magazine.


On December 7, the Ukrainian website Obozrevatel published an article titled “Scientists explain how to determine a woman’s tendency to infidelity”. The article claims:

Scientists from the University of Oxford conducted a study to find out how to determine a woman's tendency to cheat. Experts have found that women who have relationships "on the side" have a distinctive feature - the index finger on their left hand is longer than the ring finger.

Similar articles appeared in several other Ukrainian and Russian media, with headlines such as these:

Scientists determined the tendency of women to infidelity” (Life.ru);

Why do women cheat: Scientists were shocked by the results of the study” (Sputniknews.ru);

The main distinctive feature of unfaithful women was named” (Iz.ru);

Watch for the hands: how to spot the unfaithful woman” (Gazeta.ru);

As in other similar cases, the source of the story was probably the UK tabloid Daily Mail, where it appeared just a few days prior under this headline:

“How to tell if your girlfriend is a cheat? Check her FINGERS: Women with longer index fingers are MORE likely to sleep around, claim scientists”


The research mentioned in the articles was conducted at the University of Oxford. The study was published on December 5, 2018 with the title: “Associations between neurochemical receptor genes, 2D:4D, impulsivity and relationship quality”.

Researchers selected 474 participants, men and women; measured the length of their second and fourth fingers; took their saliva samples to examine DNA variations in nine neurochemical receptor genes; and gave them tests to determine a) how “impulsive” they are and b) how satisfied they are with their romantic relationships. For each sex, scientists tested whether the associations between genes, impulsivity and relationship assessment scale (RAS) are mediated by the ratio between the second and the fourth finger on the left hand (the 2D:4D ratio).

The 2D:4D ratio, as the study quotes, “has been widely used as a proxy for fetal exposure to androgens and has been linked to a number of sociosexual traits in humans.” The study concluded that genetic factors may affect both impulsivity and perceived relationship quality through influencing factors indexed by digit ratios.

“Females carrying a CC genotype for rs2075572 had higher left-hand digit ratios than G-carriers, and left-hand digit ratios were positively associated with impulsivity”, the study concludes. At the same time, such assumptions weren’t confirmed in men.

However, the “cheating” part is largely absent from the study. For a start, the researchers did not set out to find “a distinctive feature in women who have relationships on the side”, as claimed by the media. This topic was, however, indirectly mentioned in a reference to a different study, conducted in 2015. That study has looked into relations between finger ratio, hormones, and different “mating strategies”, i.e. tendencies of both men and women to prefer either long-term relationships, or more sexual/romantic partners.

The 2018 researchers gave no definite conclusion on relations between the two studies, stating, instead, that the measured higher level of impulsivity and/or dissatisfaction with their relationship “might” be related to women’s “more feminized morphology and higher ‘mate value” and lead to “impulsive extra-pair matings and seeking alternative mates”:

“According to these results, women with higher (more feminine) left-hand digit ratios [2nd finger longer than the 4th] are more impulsive and rate their romantic relationships less favourably. The direction of this relationship is intriguing, because the opposite might be expected. However, recent work suggests that both sexes follow one of two distinct mating strategies, one promiscuous and one focusing on long-term commitment. If females with more feminized morphology have higher ‘mate value', this might be associated with dissatisfaction with current partners, leading to impulsive extra-pair matings and seeking alternative mates.”

Moreover, the researchers who conducted the 2015 study themselves pointed out that their assumptions have to be further tested with additional studies. One of the coauthors of the research, Rafael Wlodarski, had this to say about it:

“'Many dozens of factors combine to affect how promiscuous you are’. He added that those factors range from your friendships and personality traits to your culture and environment. Rafael Wlodarski added as well that finger length may be able to predict promiscuity when applied to big groups of people. But at the individual level, it’s just one of many variables.“

A similar “disclaimer” has also been given in the 2018 study, which notes that the findings are preliminary and require further research:

“Although these findings are subject to multiple testing issues, this study provides preliminary evidence that in women genetic factors may affect both impulsivity and perceived relationship quality through influencing factors indexed by digit ratios.”

In short, there are multiple “ifs” and “mights” between the conclusions of the study and the sensationalist claims that finger length is an unmistakable sign that someone is cheating, or prone to cheating.


“Mashing” together results of different studies and incorrectly presenting them as one study’s conclusion - which applies to all women and every woman individually - build up to an inaccurate presentation of each of these studies’ results. We rate that as manipulation of facts and pseudoscience. The accompanying sensationalist headlines, claiming that you can “spot an unfaithful woman”, “discover if your wife is faithful to you”, or “why women cheat” by looking at their fingers, we also rate as clickbait.


Project #Femfacts co-financed by European Commission Directorate-General for Communications Networks, Content and Technology as part of the Pilot Project – Media Literacy For All

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