Finger length ratios fail to predict men’s behavior toward women
A 2015 study found that men with a lower second-to-fourth finger ratio reported more agreeable and fewer quarrelsome interactions with women. The measure is only an indirect proxy for prenatal hormone exposure, and the original result was correlational rather than causal. The article concludes that finger ratios do not reliably predict how men treat women.
The 2015 work tracked 155 people for 20 days, asking them to record social encounters longer than five minutes and mark agreeable or quarrelsome acts. Men with smaller 2D:4D ratios reported about one-third more agreeable and one-third fewer quarrelsome behaviors. The ratio is only an indirect marker of prenatal hormone exposure, and the finding was correlational.
A 2021 replication with 81 participants, including relatively few men, did not reproduce the male digit-ratio effect. A 2019 study of 560 people in real-money economic games also found no robust link between 2D:4D and generosity, bargaining, punishment, trust, or reciprocity.
This story may temper popular claims that finger proportions reveal how men will treat women. People who encounter such claims—daters, coworkers, or readers of pop-science—could be less likely to treat 2D:4D as a reliable personality test. Because the evidence is correlational and replication is mixed, any societal impact is likely modest: it may discourage overinterpretation rather than change policy or practice.