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Digit ratio

Author: Dr Simon Moss

Overview of the second-to-fourth digit ratio

The second-to-fourth digit ratio refers to the length of the index finger relative to the ring finger. According to a broad gamut of studies, this ratio, determined by the level of prenatal testosterone, can predict a diversity of personality traits. In particular, individuals whose index finger is almost as long--or even longer--than is their ring finger are more likely to demonstrate characteristics that are typical of females. Even their writing tends to be more feminine in style (Beech & Mackintosh, 2005). Usually, but not always, these observations apply to the right hand only (for a review, see Kuepper & Hennig, 2007).

Digit ratio and personality

Emotions and aggression

A high second-to-fourth digit ratio--in other words, relatively long index fingers--corresponds to lower levels of aggression (Kuepper & Hennig, 2007), at least in men, as well as lower levels of psychoticism (Austin, Manning, McInroy, & Matthews, 2002). When the index finger is relatively long, the personality trait referred to as agreeableness is usually elevated (Luxen & Buunk, 2005).

Depression, however, is more likely to surface instead (Bailey & Hurd, 2005) as is anxiety, distress, and frustration (Fink, Manning, & Neave, 2004) as well as emotional problems in general (Williams, Greenhalgh, & Manning, 2003).

Retribution

As Ronay and Galinsky (2011) showed, the relative length of ring fingers, relative to index fingers, seems to be more related to retribution of injustice rather than unjustified aggression. That is, a long ring finger, corresponding to elevated levels of testosterone before birth, increase the likelihood of aggressive responses but only in response to unfair behaviour.

For example, in one study, participants completed the ultimatum game (see also games). Another person, actually a confederate of the researchers, was granted $40. This person was told to share some of the $40 with the participant. This confederate decided to share either $20 or $5. Participants could then either accept or reject the offer. If they accepted the offer, both people received their allocated distributions. If they rejected the offer, nobody received any of the money. People sometimes refuse the money, sacrificing their own financial interests, as a form of protest against injustice.

Next, participants were then told they will be granted the opportunity to share the $40 with the other person. That is, the game was repeated, but the roles were reversed.

If the digit ratio was low, indicating high levels of testosterone before birth, participants were more likely to demonstrate retribution. That is, they shared less money with the other person, but only if they had been offered $5 instead of $20 in the previous trial. Furthermore, they shared less money only if they perceived the other person as unfair (Ronay & Galinsky, 2011).

These findings indicate that testosterone might evoke aggression only when provoked. Specifically, testosterone might increase the need of individuals to seek retribution. Similarly, testosterone has been shown to compromise circuits in the orbitofrontal cortex that underpin self control--that is, individuals may act aggressively in response to provocations, but sometimes to the detriment of their future needs (Mehta & Beer, 2010).

Temperament

According to Fisher, Rich, Island, and Marchalik (2010), digit ratio might predict the temperament of individuals--that is, traits and attributes that are strongly associated with biological systems. Specifically, Fisher, Rich, Island, and Marchalik (2010) emphasized that traits can be ascribed to four distinct neural systems, corresponding to testosterone, estrogen or oxytocin, dopamine or norepinephrine, as well as serotonin, respectively.

Each of these four systems is associated with a set of traits. To illustrate, as Fisher, Rich, Island, and Marchalik (2010) summarized, testosterone levels, either before birth or during adulthood, are associated with spatial ability, mathematical skills, attention to detail, a restricted range of interests, impaired emotional recognition, limited sensitivity to the needs and emotions of other people, disrespectful behavior, and aggressive or dominant inclinations. Estrogen levels are associated with nurturance and helping as well as verbal skills.

In one study, conducted by Fisher, Rich, Island, and Marchalik (2010), participants answered a series of questions that assess the extent to which these four systems are activated. For example, to assess the testosterone system, questions related to the extent to which participants understand complex machines, enjoy competition, disregard emotions, and feel tough. To assess the estrogen or oxytocin system, participants were asked to specify the degree to which they like to share their feelings to friends, enjoy intimacy, trust their intuition, demonstrate a vivid imagination, and monitor the feelings of other people. Furthermore, to assess the dopaminergic system, questions revolved around the extent to which individuals enjoy unfamiliar, exhilarating, energetic, and risky settings as well as seem optimistic and creative. Finally, to assess the serotonergic system, the questions related to the degree to which individuals are meticulous, conservative, orderly, and traditional.

Interestingly, two of these systems were associated with digit ratio. In particular, as predicted, a long ring finger, relative to the index finger, corresponded to characteristics that are associated with elevated levels of testosterone. A longer index finger, in contrast--or an index finger that is similar in length to the ring finger--was associated with traits that are associated with elevated levels of estrogen or oxytocin.

Interests

A high second-to-fourth digit ratio, which often corresponds to feminine traits, also corresponds to a preference to leadership roles or manual tasks (Weis, Firker, & Hennig, 2007). That is, when the index finger is relatively long, individuals do not enjoy realistic or enterprising tasks, as defined by Holland.

Digit ratio and ability

Second-to-fourth digit ratio also coincides with ability. Individuals who exhibit a long index finger, relative to their ring finger tend to demonstrate advanced verbal, but not numerical, skills (Luxen & Buunk, 2005). In contrast, individuals who exhibit a short index finger often exhibit superior spatial performance on visual tasks (Manning & Taylor, 2001).

Digit ratio and prenatal testosterone

The second-to-fourth digit ratio has been shown to correlate with the level of testosterone in individuals before they were born, as measured in the amniotic fluid (Lutchmaya, Baron-Cohen, Raggatt, Knickmeyer, & Manning, 2004), and these testosterone levels are assumed to influence their brain and, ultimately, their behavior. Prenatal testosterone seems to lengthen the ring finger, whereas prenatal estrogen lengthens the index finger (Manning, Scutt, Wilson, & Lewis-Jones, 1998).

Considerable evidence has accrued that supports this contention that prenatal testosterone corresponds to this ratio. For instance, a disorder called congenital adrenal hyperplasia augments exposure to testosterone during the gestation period and also corresponds to shorter index fingers relative to ring fingers (Brown, Hines, Fane, & Breedlove, 2002. The second-to-fourth digit ratio is higher in women than men& that is, the index finger of women is more likely to be as long as, or even longer, than is their ring finger (for reviews, see Kuepper & Hennig, 2007& Voracek & Pavlovic, 2007).

Furthermore, research shows that testosterone prenatally corresponds to masculine traits and characteristics later in life. Females exposed to excess testosterone or other androgens demonstrated behavior that is typical of males during their infancy and report homosexual or bisexual fantasies later in life (Hines, 2000).

Practical implications

In the context of recruitment, assessors could ask the job applicants to create a trace of their right hand. Applicants whose right ring finger is appreciably longer than is their right index finger might be more suited to roles that demand excellent numerical skills as well as defiance or dominance and receptivity to stress, change and uncertainty. Applicants whose right index finger is appreciably longer than is their right ring finger might be more suited to roles that demand compassion, understanding, and sympathy.

Related concepts

Facial width to height ratio

The face of some people is quite wide. That is, the width, relative to the height, of their face, is greater than average. These individuals are more likely to express racist attitudes rather than to inhibit their natural tendencies. They may, for example, agree with statements like "I would rather not have Blacks live in the same apartment building I live in" (Hehman, Leitner, Deegan, & Gaertner, 2013). However, implicit attitudes towards other races, as gauged by the implicit association test, does not seem to depend on this facial characteristic (Hehman et al., 2013).

To clarify, when testosterone levels are elevated, especially during puberty and adolescence, individuals are more likely to develop a wider face. Therefore, facial width is perhaps an index of exposure to testosterone. These elevated levels of testosterone are associated with social dominance, diminishing the tendency of people to inhibit their natural tendencies. Consequently, when faces are wide and testosterone levels are elevated, individuals will express, rather than inhibit, their biases (Hehman, Leitner, Deegan, & Gaertner, 2013). But, they may not be more likely than other people to be susceptible to these biases.

References

Austin, E. J., Manning, J. T., McInroy, K., & Mathews, E. (2002). An investigation of the association between personality, cognitive ability and digit ratio. Personality and Individual Differences, 33, 1115-1124.

Bailey, A. A., & Hurd, P. L. (2005). Depression in men is associated with more feminine finger length ratios. Personality and Individual Differences, 39, 829-836.

Beech, J. R., & Mackintosh, I. C. (2005). Do differences in sex hormones affect handwriting style? Evidence from digit ratio and sex role identity as determinants of the sex of handwriting. Personality and Individual Differences, 39, 459-468.

Brown, W. M., Hines, M., Fane, B. A., & Breedlove, S. M. (2002). Masculinized finger-length patterns in human males and females with congenital adrenal hyperplasia. Hormones and Behavior, 42, 380-386.

Csatho, A., Osvath, A., Bicsak, E., Karadi, K., Manning, J., & Kallai, J. (2003). Sex role identity related to the ratio of second to fourth digit length in women. Biological Psychology, 62, 147-156.

Fink, B., Manning, J. T., & Neave, N. (2004). Second to fourth digit ratio and the 'big five' personality factors. Personality and Individual Differences, 37, 495-503.

Fisher, H. E., Rich, J., Island, H. D., & Marchalik, D. (2010). The second to fourth digit ratio: A measure of two hormonally-based temperament dimensions. Personality and Individual Differences, 49, 773-777.

Hall, L. S., & Love, C. T. (2003). Finger length ratios in female monozygotic twins discordant for sexual orientation. Archives of Sexual Behavior, 32, 23-28.

Hehman, E., Leitner, J. B., Deegan, M. P., & Gaertner, S. L. (2013). Facial structure is indicative of explicit support for prejudicial beliefs. Psychological Science, 24, 289-296. doi: 10.1177/0956797612451467

Hines, M. (2000). Gonadal hormones and sexual differentiation of human behaviour: effects on psychosexual and cognitive development. In A. Matsumoto (Ed.), Sexual differentiation of the brain (pp. 257-278). Florida: CRC Press.

Kempel, P., Gohlke, B., Klempau, J., Zinsberger, P., Reuter, M., & Hennig, J. (2005). Second-to-fourth digit length, testosterone and spatial ability. Intelligence, 33, 215-230.

Kratochvil, L., & Flegr, J. (2009). Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biology Letters, 5, 643-646.

Kuepper, Y., & Hennig, J. (2007). Behavioral aggression is associated with the 2D:4D ratio in men but not in women. Journal of Individual Differences, 28, 64-72.

Lippa, R. A. (2006). Finger length, 2D:4D ratios, and their relation to gender-related personality traits and the Big five. Biological Psychology, 71, 116-121.

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, 23-28.

Luxen, M. F., & Buunk, B. P. (2005). Second-to-fourth digit ratio related to verbal and numerical intelligence and the big five. Personality and Individual Differences, 39, 959-966.

Malas, M. A., Dogan, S., Evcil, E. H., & Desdicioglu, K. (2006). Fetal development of the hand, digits and digit ratio (2D:4D). Early Human Development, 82, 472-475.

Manning, J. T. (2002). Digit ratio: A pointer to fertility, behavior and health. New Jersey: Rutgers University Press.

Manning, J. T., Baron-Cohen, S., Wheelwright, S., & Fink, B. (2010). Is digit ratio (2D:4D) related to systemizing and empathizing? Evidence from direct finger measurements reported in the BBC internet survey. Personality and Individual Differences, 48, 767-771.

Manning, J. T., Bundred, P. E., Newton, D. J., & Flanagan, B. F. (2003). The second to fourth digit ratio and variation in the androgen receptor gene. Evolution and Human Behavior, 24, 399-405.

Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and concentrations of testosterone, luteinizing hormone, and estrogen. Human Reproduction, 13, 3000-3004.

Manning, J. T., & Taylor, R. P. (2001). Second to fourth digit ratio and male ability in sport: implications for sexual selection in humans. Evolution and Human Behavior, 22, 61-69.

Mehta, P., & Beer, J. (2010). Neural mechanisms of the testosterone-aggression relation: The role of the orbitofrontal cortex. Journal of Cognitive Neuroscience, 22, 2357-2368.

Okten, A., Kalyoncu, M., & Yaris, N. (2002). The ratio of second-and-fourth digit length and congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Early Human Development, 70, 47-54.

Rahman, Q., & Wilson, G. D. (2003). Sexual orientation and the 2nd to 4th finger length ratio: Evidence for organising effects of sex hormones or development instability? Psychoneuroendocrinolgy, 28

Ronay, R., & Galinsky, A. D. (2011). Lex talionis: Testosterone and the law of retaliation. Journal of Experimental Social Psychology, 47, 702-705. oi:10.1016/j.jesp.2010.11.009

Voracek, M., & Pavlovic, S. (2007). The tell-tale hand: The relationship of 2D:4D to perceived attractiveness, sex typicality, and other attributes of palms. Journal of Individual Differences, 28, 88-97.

Weis, S. E., Firker, A., & Hennig, J. (2007). Associations between the second to fourth digit ratio and career interests. Personality and Individual Differences, 43, 485-493.

Williams, J. H. G., Greenhalgh, K. D., & Manning, J. T. (2003). Second to fourth digit ratio and possible precursors of developmental psychopathology in preschool children. Early Human Development, 72, 57-65.

Williams, T. J., Pepitine, M. E., Christensen, S. E., Cooke, B. M., Huberman, A. D., Breedlove, N. J., et al. (2000). Finger length ratio and sexual orientation. Nature, 404, 455-456.



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Last Update: 6/8/2016