Second To Fourth Digit Ratio

[Michael Scally MD]

Kim Y, Kim K, Kim TH. Domain Specific Relationships of 2D:4D Digit Ratio in Risk Perception and Risk Behavior. J Gen Psychol 2014;141(4):373-92. http://www.tandfonline.com/doi/full/10.1080/00221309.2014.950188

The 2D:4D digit ratio (henceforth, 2D:4D) is accepted as a marker of prenatal testosterone, demonstrating gender differences.

The present study reveals that 2D:4D shows not only gender differences but also individual differences in personality and risk-taking behavior.

We measured individual participants' 2D:4D, structural personality, and risk-taking attitude scores. The result of the current study replicates the gender difference in 2D:4D in previous researches.

However, we found different aspects of the correlations among 2D:4D, personality, and risk-taking attitude.

Path analyses indicated that 2D:4D passes through personality factors before reaching the risk-taking attitude, particularly in the financial domain activities of investing and gambling.

Also we observed a specific relationship between right-hand 2D:4D and emotionality and between left-hand 2D:4D and agreeableness.

Finally, we suggest multiple path models of 2D:4D and personality in risk taking depending on the domain.

 

[Michael Scally MD]

[ROTFLMAOPIMP]

Highlights
• Smaller 2D:4D ratios reflect greater prenatal androgen exposure.
• We examined associations among 2D:4D ratios, agreeableness, and gender of partner.
• Men with smaller digit ratios showed greater agreeableness with women than with men.
• Men with smaller digit ratios showed lower quarrelsomeness with women than with men.
• Fetal androgen exposure affects context specific aspects of men’s social behavior.

Moskowitz DS, Sutton R, Zuroff DC, Young SN. Fetal exposure to androgens, as indicated by digit ratios (2D:4D), increases men’s agreeableness with women. Personality and Individual Differences, 2015;75:97. https://www.sciencedirect.com/science/article/pii/S0191886914006400

The ratio of the length of the second finger, or digit, to the fourth finger (2D:4D) is influenced by fetal exposure to androgens; a smaller ratio indicates greater androgen exposure.

We used event contingent recording to investigate the relation between the 2D:4D ratio and social behavior.

Participants completed multiple records of their behavior in events in naturalistic settings; records included information about situational features such as the gender of the person with whom the person was interacting.

Men were more agreeable towards women than men; this effect was significantly greater in those with smaller 2D:4D ratios.

Men with smaller 2D:4D ratios were also less quarrelsome towards women than towards men. The 2D:4D ratio did not influence social behavior in women.

The hormonal environment in which the male fetal brain develops may influence adult social behavior in specific contexts.

 

[BBC3]

2 Points...:

It still remains unclear the finger difference we are looking for. Two guys corrected me earlier stating a bigger difference meant more T "in utero. But I keep reading that the SMALLER RATIO (Which I interpret as VARIANCE) means MORE..?? Anyone got the balls to STAMP THEIR NAME ON A CLARIFICATION>>>???

Second. I always assumed they are MEASURING but looking at the lengths of digits at FINGERTIPS. But this only defines the SHAPE of the HAND. Are they measuring the length of the fingers from fist knuckle to finger tip by any chance... Cause thats two different stories..??

 

[56HUNTER]

this only references length.... most women love girth...do these studies also pertain to thickness?

 

[Michael Scally MD]

Xie W, He M, Liu R, Dong Z, Xie J, et al. The second to fourth digit ratio (2D:4D): a risk factor of migraine and Tension-type headache. J Headache Pain. 2015;16(1):494. http://link.springer.com/article/10.1186/s10194-015-0494-8

BACKGROUND: Migraine and Tension-type headache (TTH) are common and disabling primary headache disorders. They are more prevalent in females. The second to fourth digit ratio (2D:4D) is sexually dimorphic in humans and is considered to be a marker for the balance of prenatal testosterone and estrogen exposure. Therefore, we investigated the hypothesis that prenatal sex steroids constitute an independent risk factor for adult headaches later in life.

METHODS: A total of 891 individuals (303 males, 588 females) of 18-68 years in age (a mean of 37.0 +/- 10.1 years), including 279 migraine, 300 TTH, and 312 healthy subjects were enrolled. The 2D:4D ratio was measured by a single investigator using a digital Vernier caliper.

RESULTS: The females in the migraine group had lower 2D:4D ratios than those in the control group (left hand: 0.947 +/- 0.034 vs. 0.955 +/- 0.038, p = 0.048; right hand: 0.952 +/- 0.035 vs. 0.965 +/- 0.037, p = 0.001).

There was a similar relationship between the TTH group and the control group (left hand: 0.946 +/- 0.034 vs. 0.955 +/- 0.038, p = 0.034; right hand: 0.954 +/- 0.035 vs. 0.965 +/- 0.037, p = 0.005), although this was not observed in males. Males showed lower 2D:4D ratios than females for the right hand in the control group (0.954 +/- 0.039 vs. 0.965 +/- 0.037, p = 0.015). No significant difference was found in the left hand.

CONCLUSIONS: These results suggested that the 2D:4D ratio is a risk factor of migraine and TTH and that the balance of prenatal estrogen and testosterone in utero may impact adult primary headache disorders.

 

[Michael Scally MD]

Tomkinson JM, Tomkinson GR. Digit ratio (2D:4D) and muscular strength in adolescent boys. Early Human Development 2017;113:7-9. Digit ratio (2D:4D) and muscular strength in adolescent boys - ScienceDirect

Highlights
· This was the first study to describe the relationship between digit ratio (2D:4D) and handgrip strength in adolescent boys.
· 2D:4D was very likely a moderate negative correlate of handgrip strength, even after adjustment for age and body size.
· This result may reflect the organizational benefits of prenatal testosterone.

Using a cross-sectional design, this study quantified the relationship between the digit ratio (2D:4D) and muscular strength in 57 adolescent boys. 2D:4D was very likely a moderate negative correlate of handgrip strength, even after adjustment for age and body size. This result may reflect the organizational benefits of prenatal testosterone.

 

[Michael Scally MD]

Kuna B, Galbarczyk A. Men with more masculine digit ratios are partnered with more attractive women. Personality and Individual Differences 2018;124:8-11. Men with more masculine digit ratios are partnered with more attractive women

Highlights
· Men's prenatal environment may have long-lasting influences on their mating value.
· Men's 2D:4D may be linked with their actual partners' anthropometric traits.
· Women partnered with men with lower 2D:4D have significantly narrower waists.

The low 2nd to 4th digit ratio (2D:4D) is thought to reflect higher prenatal exposure to testosterone and may be associated with higher testosterone levels in adulthood and higher reproductive success in males. However, there is little evidence that higher testosterone levels are directly responsible for higher male fertility.

Here, we investigate if this phenomenon may be related to mate choice, and, in particular, if males with lower 2D:4D are partnered with more attractive and potentially more fertile women. We compared waist-to-hip ratio and breast size of 50 women from two groups, depending on the 2D:4D (more masculine, more feminine) of their actual partner. Moreover, we examined the relationship between men's digit ratio and their mate's body type.

Men with more masculine 2D:4D were coupled with women with significantly lower waist-to-hip ratios. They were also four times more often partnered with women who had both relatively narrow waists and large breasts.

These findings suggest that levels of sex steroids during fetal development in males may have long-lasting influences on their mating value. This is the first study to show relationships between men's intrauterine environment, reflected by 2D:4D, and their actual partners' anthropometric traits, linked to perceived attractiveness and potential fertility.

 

[Michael Scally MD]

Digit Ratio (2D:4D) and Testosterone Supplementation

Highlights
· We considered the relationship between prenatal sex steroids, as measured by the digit ratio (2D:4D), and testosterone supplementation (T or HRT with T)
· Our sample is drawn from a large online survey (the BBC Study). T supplementation was most common in young males and HRTwT most common in older females.
· Males who took T and HRTwT had higher right 2D:4D and higher right-left 2D:4D than their counterparts in the population.
· Effects sizes for females were much smaller and in general in the opposite direction to that of males.
· We conclude that T and HRTwT tend to be taken by high 2D:4D males, who likely have experienced low T and high estrogen in utero.

Background Testosterone (T) is taken or prescribed to enhance appearance, increase athletic performance and libido and to treat hypogonadism. Digit ratio (2D:4D) is thought to be a negative correlate of prenatal T. Here we consider the relationship between 2D:4D and T supplementation.

Aims Our sample was taken from the BBC internet study. Respondents were asked (y/n) if they were taking; (i) T, (ii) hormone replacement therapy with T (HRTwT).

We removed extreme 2D:4D values and age and considered the most numerous ethnic group (i.e. “Whites”). Analyses were performed with a two-factor (sex*T) analysis of variance with covariate age and dependent variables 2D:4D or right-left 2D:4D (Dr-l).

Results Out of 197,589 respondents, 793 (598 males) reported taking T. There was a significant main effect for right 2D:4D such that T supplementing males had higher 2D:4D than those who did not. The sex*T interaction was significant, but the effect reversed in females. There were 22,576 (661 males) participants who reported taking HRTwT.

We found a significant main effect for right 2D:4D, males taking HRTwT had higher 2D:4D than those who did not. This was reversed in females. The sex*HRTwT interaction was significant, a high Dr-l was also found in males reporting HRTwT.

Conclusion Males who reported taking T or HRTwT had high right 2D:4D and/or Dr-l. The situation with females may be the reverse of that found in males but effect sizes are less. The health implications of an association between high (feminized) 2D:4D and T supplementation in males are discussed.

Manning J, Cook C, Crewther B. Digit ratio (2D:4D) and testosterone supplementation. Early Human Development 2019;139:104843. https://www.sciencedirect.com/science/article/pii/S0378378219303548