New Study Finds Shocking Link Between Finger Length and Psychopathy

Cropped photo of a man in a navy blue suit holding out the palm of his hand — Bits And Splits / Shutterstock

Manipulation, aggression, and lack of empathy are just a few of the key warning signs that can help identify a psychopath in your life. Naturally, if you're just getting to know the person—like on a date— those red flags may not visibly present themselves right away. However, research suggests that there is a new and faster way to spot a psychopath, and it all comes down to the length of their index finger and ring finger, specifically on the right hand.

Published in next month's edition of the Journal of Psychiatric Research, mental health researchers conducted a study in which they took scans of the right hands of 80 volunteers to deduce whether psychology is "biologically rooted." Of the participants, 44 had been previously diagnosed with psychiatric issues.

The correlation between the clinically diagnosed volunteers and the length of their fingers compared to the other tested individuals seemingly proves that psychopathy is more common amongst those with a shorter index finger and longer ring finger, referred to as "a lower 2D:4D ratio."

Researchers believe that a lower 2D:4D ratio is directly related to a fetus being exposed to higher levels of testosterone and lower levels of estrogen during the first trimester.

In conclusion, the study found that those with a shorter index finger and longer ring finger were "associated with higher Dark Triad traits," which led to higher scores for "narcissism sensitivity and intolerance of uncertainty."

According to Psychology Today, Dark Triad can be best defined as "a trio of negative personality traits"—more specifically, narcissism, Machiavellianism, and psychopathy.

Other behavioral characteristics such as extreme competitiveness and aggression also became discernable in this group. Per the study, adults with a lower 2D:4D ratio "scored high on mental toughness and sports performance, but also on various types of negative psychosocial and psychological outcomes, including intolerance of uncertainty, anxiety sensitivity callous affect, and interpersonal manipulation."

It should be noted that a previous 2022 study published in the journal Heliyon that compared the right-hand 2D:4D ratio with psychopathy, found that males "exhibit lower 2D:4D ratios compared to females." Moreover, this group of researchers noted that "low 2D:4D ratios were linked with higher levels of egocentricity in males compared to females."

"The topic is interesting, because the relation of the lengths of index finger (2D) and ring finger (4D) is one of the most robust biological markers formed during the prenatal stage with a remarkable impact later on an adult's behavior," Serge Brand, one of the recent study's authors, told PsyPost.

"That is to say: The more an adult participant had signs of psychopathology, the more it appeared that this adult has been exposed to higher testosterone concentrations and lower estrogen concentrations during the prenatal period of life," he explained.

However, Brand assures that simply having a shorter index finger and longer ring finger doesn't automatically mean you're a psychopath: "Rather, a lower 2D:4D-ratio and thus a higher exposure to testosterone during the prenatal period of physiological development might enable an adult person to show a specific pattern of behavior."

Emily Weaver Emily is a NYC-based freelance entertainment and lifestyle writer — though, she’ll never pass up the opportunity to talk about women’s health and sports (she thrives during the Olympics).Read moreFiled UnderMental Health • News • ScienceSources referenced in this article