woman looking in mirror
Sean Cate
Sean Cate
March 7, 2024 ·  3 min read

You May Be Able to Identify a Psychopath from This Surprising Physical Trait, Study Shows

Have you ever wondered if there’s a physical trait that could give away psychopathic tendencies? Well, according to a recent study published in the Journal of Psychiatric Research, researchers in Canada might have found one surprising new way to identify a psychopath: the length of your fingers.1

Identify a Psychopath: Getting Handsy 

The study was conducted by analyzing the finger lengths of 88 volunteers; half of the individuals were previously diagnosed with psychiatric conditions, while 36 were without any reported mental health issues. The researchers specifically focused on the ratio between the length of the index finger (2D – second digit on the hand) and the ring finger (4D – fourth digit), known as the 2D:4D ratio. They discovered that individuals with psychiatric conditions were more likely to have a shorter index finger and a longer ring finger.

Lead author Serge Brand explained, “Compared to healthy controls, individuals with a clinically diagnosed psychiatric issue were more likely to have a shorter index finger and longer ring finger.” This finding suggests a correlation between finger length and certain psychiatric traits that could, in theory, help identify a psychopath—now armed with this information, a new question forms: why?

Read More: 20+ Amazing Psychology Facts Everyone Needs to Know

Dark Triad Traits and Finger Length

The study also dug into personality traits, particularly the so-called ‘Dark Triad’ traits: Machiavellianism, narcissism, and psychopathy.2 Individuals with lower 2D:4D ratios (indicating a shorter index finger relative to the ring finger) were found to be more commonly associated with these traits. The Dark Triad traits are characterized by highly socially discouraged attitudes and behaviors, markedly including manipulation and a lack of empathy – trademark psychopathy traits.

Interestingly, those who scored high on the Dark Triad evaluation also scored high on mental toughness and sports performance but displayed various negative psychosocial and psychological outcomes. Shocking. Almost as if you could identify a psychopath based on how well they can handle sports, should we worry about Roger Federer or Simone Biles next? Quick, check their hands! 

Read More: Identifying a Narcissist – a Psychological Guide

Biological Roots of Psychopathy

The study suggests that finger length may be linked to prenatal exposure to sex hormones, particularly testosterone and estrogen.3 A lower 2D:4D ratio, indicated by higher exposure to testosterone and lower exposure to estrogen during fetal development, may contribute to the development of certain behavioral traits associated with psychopathy. So while it may not be as simple as “finger length = identify a psychopath”, it may be more of a symptom (AKA = sex hormone exposure = finger length…and also psychopathy). 

Brand emphasized that while the association between finger length and psychopathology is notable, it’s essential not to jump to conclusions. “It is important to understand that the finger lengths-ratio as a proxy of a specific exposure to prenatal sex steroids should not be understood as a person’s irrevocable fate,” Brand cautioned. Just as 10% of the world’s 7-footers play in the NBA, just because it can be, doesn’t mean it will be.

Can You Identify a Psychopath?

The length of your fingers might offer future insights into your personality traits and predispositions, particularly regarding psychopathic tendencies. However, it’s important to remember that these findings are part of ongoing research and should not be used to label individuals definitively. Finger length may provide valuable clues, but it’s just one piece of the complex puzzle that is human behavior and psychology.

So, the next time you find yourself examining your hands, remember that they might reveal more than meets the eye.

Read More: Some People May Seem “Nice” But Are Actually Psychopaths. Here Are 3 Behaviors and Their Subtleties


  1. Psychopaths are more likely to show this surprising physical trait: study.” NY Post.
    Andrew Court. January 16, 2024.
  2. 2D:4D-ratios among individuals with amphetamine use disorder, antisocial personality disorder and with both amphetamine use disorder and antisocial personality disorder.” Science Direct. Seyed Sepehr Hashemian, Senobar Golshani, Kimia Firoozabadi, Ali Firoozabadi, Christian Fichter, Kenneth M. Dürsteler, Annette B. Brühl, Habibolah Khazaie and Serge Brand. February 2024.