Editing Digit ratio (section)

==Cognitive and physical traits==
The 2D:4D ratio has been associated with a variety of traits including academic ability, personality as well as physical attributes such as health outcomes. Lower (masculinized) 2D:4D ratios have been associated with higher mathematical ability as well as personality traits such as aggressiveness (in males), assertiveness (in females) and reduced [[agreeableness]].<ref name="Jeevanandam_2016" /><ref>{{cite journal | vauthors = Luxen MF, Buunk BP | title = Second-to-fourth digit ratio related to verbal and numerical intelligence and the Big Five | journal = Personality and Individual Differences | volume = 39 | issue = 5 | pages = 959–966 | date = 2005 | pmid = | doi =  10.1016/j.paid.2005.03.016| s2cid = }}</ref><ref>{{cite journal | vauthors = Hampson E, Sankar JS | title = Re-examining the Manning hypothesis: androgen receptor polymorphism and the 2D: 4D digit ratio.  | journal = Evolution and Human Behavior | volume = 33 | issue = 5 | pages = 557–561 | date = 2012 | pmid = | doi =  10.1016/j.evolhumbehav.2012.02.003| bibcode = 2012EHumB..33..557H | s2cid = }}</ref> Males with higher (feminized) ratios are reported to be more at risk of low sperm counts, heart disease, obesity, [[metabolic syndrome]] and depression than those with lower ratios.<ref>{{cite journal | vauthors = Oyeyemi BF, Iyiola OA, Oyeyemi AW, Oricha KA, Anifowoshe AT, Alamukii NA| title =  Sexual dimorphism in ratio of second and fourth digits and its relationship with metabolic syndrome indices and cardiovascular risk factors. | journal = Journal of Research in Medical Sciences | volume = 19 | issue = 3 | pages = 234–239 | date = 2014 | pmid = 24949031| doi = | pmc = 4061645 | s2cid = }}</ref><ref>{{cite journal | vauthors = Bailey Allison A, Hurd PL | title = Depression in men is associated with more feminine finger length ratios. | journal = Personality and Individual Differences | volume = 39 | issue = 4 | pages = 829–836 | date = 2005 | pmid = | doi =  10.1016/j.paid.2004.12.017| s2cid = }}</ref><ref>{{cite journal | vauthors = Coyne SM, Manning JT, Ringer L, Bailey L | title = Directional asymmetry (right–left differences) in digit ratio (2D: 4D) predict indirect aggression in women. | journal = Personality and Individual Differences | volume = 43 | issue = 4 | pages = 865–872 | date = 2007 | pmid = | doi =  10.1016/j.paid.2007.02.010| s2cid = }}</ref> Females with higher ratios are more at risk of eating disorders, anxiety and depression.<ref>{{cite journal | vauthors = Manning JT, Kilduff LP, Trivers R | title = Digit ratio (2D: 4D) in Klinefelter's syndrome | journal = Andrology | volume = 1 | issue = 1 | pages = 94–99 | date = 2013 | pmid = 23258636| doi =  10.1111/j.2047-2927.2012.00013.x| s2cid = }}</ref>

Prenatal androgen exposure has been implicated as a determinant in left-handedness, though contradictory and inconclusive findings have been reported concerning an association between 2D:4D and left-hand dominance.<ref>{{cite journal | vauthors = Trabert B, Graubard BI, Erickson RL, Zhang Y, McGlynn KA | title = Second to fourth digit ratio, handedness and testicular germ cell tumors. | journal = Early Human Development | volume = 89 | issue = 7 | pages = 463–466 | date = 2013 | pmid = 23623693| doi =  10.1016/j.earlhumdev.2013.04.001| pmc = 3684556 | s2cid = }}</ref><ref>{{cite journal | vauthors = Lust JM, Geuze RH, Van de Beek C, Cohen-Kettenis PT, Bouma A, Groothuis TG | title = Differential effects of prenatal testosterone on lateralization of handedness and language. | journal = Neuropsychology | volume = 25 | issue = 5| pages = 581–589 | date = 2011 | pmid = 21500918| doi =  10.1037/a0023293| s2cid = }}</ref><ref>{{cite journal | vauthors = Manning JT, Peters M | title = Digit ratio (2D:4D) and hand preference for writing in the BBC Internet Study. | journal = Laterality | volume = 14 | issue = 5| pages = 528–540 | date = 2009 | pmid = 19177258| doi =  10.1080/13576500802637872| s2cid = }}</ref> Kumar ''et al.'' have reported that hand preference is most strongly associated with 3D:4D digit ratios and that the effect is reversed between children and adults.<ref>{{cite journal | vauthors = Kumar S, Singh M, Voracek M | title = Effects of hand preference on digit lengths and digit ratios among children and adults | journal = Early Human Development | volume = 151 | pages = 105204 | date = December 2020 | pmid = 33059164 | doi = 10.1016/j.earlhumdev.2020.105204 | s2cid = 222829822 | url = https://epublications.marquette.edu/math_fac/56 | access-date = 23 March 2022 | archive-date = 17 May 2022 | archive-url = https://web.archive.org/web/20220517050256/https://epublications.marquette.edu/math_fac/56/ | url-status = live | url-access = subscription }}</ref>

Fink ''et al.'' (2004) found that men with low 2D:4D ratios (indicating high testosterone) and women with high 2D:4D ratios (indicating high estrogen) express greater levels of [[facial symmetry]].<ref>{{Cite journal | vauthors = Fink B, Manning JT, Neave N, Grammer K |doi=10.1016/S1090-5138(03)00084-9 |title=Second to fourth digit ratio and facial asymmetry |date=March 2004 |journal=Evolution and Human Behavior |volume=25 |issue=2 |pages=125–32|bibcode=2004EHumB..25..125F }}</ref> The prenatal sex hormone ratio (indicated by 2D:4D) was associated with similar alterations to both male and female face shapes in utero, though the effect was three times more pronounced in males than in females.<ref>{{cite journal | vauthors = Fink B, Grammer K, Mitteroecker P, Gunz P, Schaefer K, Bookstein FL, Manning JT | title = Second to fourth digit ratio and face shape | journal = Proceedings. Biological Sciences | volume = 272 | issue = 1576 | pages = 1995–2001 | date = October 2005 | pmid = 16191608 | pmc = 1559906 | doi = 10.1098/rspb.2005.3179 }}</ref>

In a non-clinical sample of women, digit ratio correlated with [[anogenital distance]] in the expected direction. In other words, women with a greater anogenital distance, indicating greater prenatal androgen exposure, had a smaller digit ratio.<ref name="Barrett_2015">{{cite journal | vauthors = Barrett ES, Parlett LE, Swan SH | title = Stability of proposed biomarkers of prenatal androgen exposure over the menstrual cycle | journal = Journal of Developmental Origins of Health and Disease | volume = 6 | issue = 2 | pages = 149–157 | date = April 2015 | pmid = 25584807 | pmc = 5119464 | doi = 10.1017/S2040174414000646 }}</ref> Ronalds ''et al.'' (2002) showed that men who had an above average placental weight and a shorter neonatal crown-heel length had higher 2D:4D ratios in adult life.<ref>{{cite journal | vauthors = Ronalds G, Phillips DI, Godfrey KM, Manning JT | title = The ratio of second to fourth digit lengths: a marker of impaired fetal growth? | journal = Early Human Development | volume = 68 | issue = 1 | pages = 21–26 | date = June 2002 | pmid = 12191526 | doi = 10.1016/s0378-3782(02)00009-9 }}</ref>

In 2020, a paper by John T Manning and Bernhard Fink reported that at the national level, high mean male 2D:4D was associated with high [[case fatality rate]]s with [[COVID-19]], and suggested that this may be used to "identify for whom it would be advisable to exercise [[social distancing]]."<ref name="Manning_2020">{{cite journal | vauthors = Manning JT, Fink B | title = Understanding COVID-19: Digit ratio (2D:4D) and sex differences in national case fatality rates | journal = Early Human Development | volume = 146 | pages = 105074 | date = July 2020 | pmid = 32419720 | pmc = 7224643 | doi = 10.1016/j.earlhumdev.2020.105074 }}</ref> Subsequent researchers failed to replicate their findings,<ref>{{cite journal | vauthors = Jones AL, Jaeger B, Schild C | title = No credible evidence for links between 2D:4D and COVID-19 outcomes: A probabilistic perspective on digit ratio, ACE variants, and national case fatalities | journal = Early Human Development | volume = 152 | pages = 105272 | date = January 2021 | pmid = 33227636 | pmc = 7670914 | doi = 10.1016/j.earlhumdev.2020.105272 }}</ref><ref name="Jones_2020">{{cite journal | vauthors = Jones AL, Satchell LP, Jaeger B, Schild C | title = (Mis-)understanding COVID-19 and digit ratio: Methodological and statistical issues in Manning and Fink (2020) | journal = Early Human Development | volume = 148 | pages = 105095 | date = September 2020 | pmid = 32499091 | pmc = 7256504 | doi = 10.1016/j.earlhumdev.2020.105095 }}</ref> and criticised Manning and Fink for publishing papers that fail under scrutiny despite the urgent need for high quality science during the pandemic that informs medical decisions.<ref name="Jones_2020" />