Digit Ratio 2D:4D: What can Our Hands tell us?

Digit Ratio 2D:4D: What can Our Hands tell us?

What can the length of our fingers, or our digit ratio, tell us? It can serve as a predictor of physical, psychological and behavioural traits

What is the Digit Ratio?

The term describes the relationship between the length of the second (2nd digit, 2D, or index) and the fourth (digit 4, 4D, or ring) fingers.

Graphic representation of a hand

Graphic representation of a hand with measurements of the index (2D) and ring (4D) fingers.

So that:

Calculating the digit ratio


Calculating the digit ratio.

To calculate it, you only have to measure the length of both fingers, from the base (carpometacarpal joint) to the tip (end of the last phalanx), and divide the length of the index finger by the length of the ring finger.

What is the 2D:4D Ratio used for?

It’s used to assess the degree of “masculinity” characteristics you have.

While it seems strange, and it certainly is, quite a few studies show relationships between 2D:4D and physical, psychological and behavioural traits typical of an androgenic or oestrogen environment, depending on the value obtained.

Low 2D:4D Ratio, what does it mean?

A value lower than 1 is characteristic of men, and is associated with:

  • Increased risk of diseases characteristic of the male sex (cardiovascular, prostate cancer, etc.)
  • Increased addiction traits.
  • More aggression
  • Greater leadership and group management capacity.
  • Tendency for polygamy and infidelity.

Histogram digital ratio

Histogram showing the distribution of subjects in both sexes and their digital ratio.

According to a study in the University of Alberta where they related this relationship to some health markers, in humans, the average is

  • 9.947 in men.
  • 9.965 in women.

With a statistically significant difference, which means that in a uniformly distributed way, men have a lower ratio than women.

Serena Williams

This isn’t to say that a woman can’t have a smaller 2D:4D ratio, just that it’s less common.

In certain studies it has been associated with sexual orientations of men with a less masculine appearance and/or women (homosexuality), polycystic ovary syndrome, more assertiveness, relevant decision-making capacity and athletic performance.

You hand reveals thing about you: finger theory

Finger theory is just a colloquial way of describing the phenomenon that associates the 2D:4D ratio with certain characteristic features when, in principle, there should be no reason to do so.

This is part of the study of palmistry, a pseudoscience based on the fact that our hands contain relevant information about our health, our way of being, our behaviour and our future.

Something that has not been rigorously demonstrated in any study carried out in a university of recognised transparency.

Digital ratio children

Perhaps our hands can provide at least some information about us and our way of acting.

This is why index-to-ring is such a strange phenomenon, since it has a great density of experimental evidence in animal models, and observational evidence in humans, which correlates it with certain aspects, such as those described above, in a sufficiently homogeneous way to think that it could in fact be a real factor..

What happens if my ring finger is larger than my index??

It’s OK to have your ring finger bigger than your index finger, i.e. a bigger 2D:4D.

It is possible that you’ll be more susceptible to:

  • Lower fertility (in men)
  • Higher risk of central and visceral obesity.
  • Higher risk of depression.
  • Increased prevalence of psychopathy.
  • Worse sporting performance.
  • Improved verbal fluency and average IQ.
  • Tendency towards neuroticism and anxiety traits.
Even so, the results reported in certain studies should be interpreted with caution, as there does not seem to be a clear causal relationship, and it is possible that the 2D:4D ratio is not really as decisive as it may seem a priori.

Ring finger and testosterone

The reason behind the relationship between these fingers is that the ring finger has a higher density of androgen receptors (to which hormones such as testosterone are bound), while the index finger has an increased density of oestrogen receptors (to which mainly oestrone, estriol and estradiol are bound).

Hormone predominance

Hormone predominance and associated receptor density in the fingers, resulting in a male/female phenotype depending on their relationship.

Hence foetal exposure to hormones during the specific process of finger development conditions the length of the ring finger, and the digit ratio, with the effects described above.

Those foetuses that are exposed to a higher concentration of androgens (such as testosterone) in the amniotic fluid have a lower 2D:4D ratio.

Bibliographic References

  1. Eklund, E., Ekström, L., Thörngren, J. O., Ericsson, M., Berglund, B., & Hirschberg, A. L. (2020). Digit Ratio (2D:4D) and Physical Performance in Female Olympic Athletes. Frontiers in Endocrinology, 11, 292.
  2. Lutchmaya, S., Baron-Cohen, S., Raggatt, P., Knickmeyer, R., & Manning, J. T. (2004). 2Nd To 4Th Digit Ratios, Fetal Testosterone and Estradiol. Early Human Development, 77(1–2), 23–28.
  3. Wlodarski, R., Manning, J., & Dunbar, R. I. M. (2015). Stay or stray? Evidence for alternative mating strategy phenotypes in both men and women. Biology Letters, 11(2), 20140977.
  4. Zheng, U., & Cohn, M. J. (2011). Developmental basis of sexually dimorphic digit ratios. Proceedings of the National Academy of Sciences of the United States of America, 108(39), 16289–16294.
  5. Tabachnik, M., Sheiner, E., & Wainstock, T. (2020). The association between second to fourth digit ratio, reproductive and general health among women: findings from an Israeli pregnancy cohort. Scientific Reports, 10(1), 6341.
  6. Bailey, A. A., & Hurd, P. L. (2005). Finger length ratio (2D:4D) correlates with physical aggression in men but not in women. Biological Psychology, 68(3), 215–222.

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About Alfredo Valdés
Alfredo Valdés
He is a specialist in metabolic physiopathology training and in the biomolecular effects of food and physical exercise.
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