Relationship between the 2D:4D and prenatal testosterone, adult level testosterone, and testosterone change: Meta-analysis of 54 studies.

2D:4D adult digit ratios prenatal testosterone testosterone change

Journal

American journal of biological anthropology

ISSN: 2692-7691

Titre abrégé: Am J Biol Anthropol

Pays: United States

ID NLM: 101770171

Informations de publication

Date de publication:
05 Oct 2023

Historique:

revised: 29 08 2023

received: 06 08 2022

accepted: 12 09 2023

medline: 5 10 2023

pubmed: 5 10 2023

entrez: 5 10 2023

Statut: aheadofprint

Résumé

The ratio between the hands' second to the fourth finger (2D:4D) is commonly hypothesized to result from prenatal testosterone. The 2D:4D has also been hypothesized to relate to adult-level testosterone and, more recently, to the testosterone response to a challenging situation. In the present work, we tested these core assumptions. Drawing from, in total, 54 studies and 8077 participants, we investigated whether the 2D:4D is related to adult level testosterone (44 studies), testosterone change (6 studies), and prenatal testosterone (10 studies). We found no evidence of the relationship between the above testosterone types and digit ratios. Furthermore, there was no relationship between testosterone and the right and left 2D:4D, male and female 2D:4D, and the 2D:4D and testosterone measurement (i.e., measured in blood or saliva). However, we found some evidence that prenatal testosterone measured in amniotic fluid (but not cord blood) might be related to the digit ratios-further studies are necessary to validate this observation. In summary, considering the current state of knowledge, any conclusions drawn from the assumption of the digit ratios as the proxy for testosterone (prenatal, adult level, or testosterone change under a challenging situation) warrant great caution.

Identifiants

DOI: 10.1002/ajpa.24852 PMID: 37795916

pubmed: 37795916

doi: 10.1002/ajpa.24852

doi:

Types de publication

Journal Article Review

Langues

eng

Sous-ensembles de citation

Subventions

Organisme : IDN Being Human Lab, University of Wrocław, Poland

Informations de copyright

Références

Almasry, S. M., el Domiaty, M. A., Algaidi, S. A., Elbastawisy, Y. M., & Safwat, M. D. (2011). Index to ring digit ratio in Saudi Arabia at Almadinah Almonawarah province: A direct and indirect measurement study. Journal of Anatomy, 218(2), 202-208. https://doi.org/10.1111/J.1469-7580.2010.01318.X

Altman, D. G., & Bland, J. M. (1995). Statistics notes: Absence of evidence is not evidence of absence. BMJ, 311(7003), 485. https://doi.org/10.1136/BMJ.311.7003.485

Apalkova, Y., Butovskaya, M. L., Shackelford, T. K., & Fink, B. (2021). Personality, aggression, sensation seeking, and hormonal responses to challenge in Russian alpinists and special operation forces. Personality and Individual Differences, 169, 110238. https://doi.org/10.1016/j.paid.2020.110238

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. https://doi.org/10.1016/J.BIOPSYCHO.2004.05.001

Bang, A. K., Carlsen, E., Holm, M., Petersen, J. H., Skakkebaaek, N. E., & Jørgensen, N. (2005). A study of finger lengths, semen quality and sex hormones in 360 young men from the general Danish population. Human Reproduction, 20(11), 3109-3113. https://doi.org/10.1093/HUMREP/DEI170

Barel, E. (2019). 2D:4D, optimism, and risk taking. Current Psychology, 38(1), 204-212. https://doi.org/10.1007/s12144-017-9598-4

Barut, C., Tan, Ü., & Dogan, A. (2008). Association of height and weight with second to fourth digit ratio (2D:4D) and sex differences. Perceptual and Motor Skills, 106(2), 627-632. https://doi.org/10.2466/PMS.106.2.627-632

Begg, C. B., & Mazumdar, M. (1994). Operating characteristics of a rank correlation test for publication bias. Biometrics, 50(4), 1088-1101. https://doi.org/10.2307/2533446

Benderlioglu, Z., & Nelson, R. J. (2004). Digit length ratios predict reactive aggression in women, but not in men. Hormones and Behavior, 46(5), 558-564. https://doi.org/10.1016/J.YHBEH.2004.06.004

Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2021). Introduction to meta-analysis (2nd ed.). Wiley.

Borkowska, B., & Pawlowski, B. (2013). Alcohol and nicotine intake and prenatal level of androgens measured by digit ratio. Personality and Individual Differences, 55(6), 685-687. https://doi.org/10.1016/J.PAID.2013.05.020

Borniger, J. C., Chaudhry, A., & Muehlenbein, M. P. (2013). Relationships among musical aptitude, digit ratio and testosterone in men and women. PLoS One, 8(3), e57637. https://doi.org/10.1371/JOURNAL.PONE.0057637

Borráz-León, J. I., Cerda-Molina, A. L., Choi, D., & Mayagoitia-Novales, L. (2018). Testosterone and intrasexual competition in men: Is there any relation with digit ratio (2D:4D)? Acta Ethologica, 21(2), 137-140. https://doi.org/10.1007/s10211-018-0284-9

Borráz-León, J. I., Rantala, M. J., & Cerda-Molina, A. L. (2019). Digit ratio (2D:4D) and facial fluctuating asymmetry as predictors of the dark triad of personality. Personality and Individual Differences, 137, 50-55. https://doi.org/10.1016/J.PAID.2018.08.008

Brañas-Garza, P., Espín, A. M., García-Muñoz, T., & Kovářík, J. (2019). Digit ratio (2D: 4D) and prosocial behaviour in economic games: no direct correlation with generosity, bargaining or trust-related behaviours. Biology Letters, 15(8), 20190185. https://doi.org/10.1098/rsbl.2019.0185

Butovskaya, M., Burkova, V., Karelin, D., & Fink, B. (2019). Personal communication.

Campbell, B. C., Dreber, A., Apicella, C. L., Eisenberg, D. T. A., Gray, P. B., Little, A. C., Garcia, J. R., Zamore, R. S., & Lum, J. K. (2010). Testosterone exposure, dopaminergic reward, and sensation-seeking in young men. Physiology & Behavior, 99(4), 451-456. https://doi.org/10.1016/J.PHYSBEH.2009.12.011

Candelo, N., & Eckel, C. (2018). The 2D:4D ratio does not always correlate with economic behavior: A field experiment with African-Americans. Economics & Human Biology, 30, 172-181. https://doi.org/10.1016/J.EHB.2018.07.002

Çetİn, R., Can, M., & Özcan, E. (2016). Yenİdoğanlarda 2D:4D parmak uzunluklari orani İle kordon kani testosteron ve östrojen hormonu sevİyesİ arasindakİ İlİşkİ. Balıkesir Sağlık Bilimleri Dergisi, 5(2), 75-82. https://dergipark.org.tr/en/pub/balikesirsbd/issue/38438/452582

Chen, C., Decety, J., Huang, P. C., Chen, C. Y., & Cheng, Y. (2016). Testosterone administration in females modulates moral judgment and patterns of brain activation and functional connectivity. Human Brain Mapping, 37(10), 3417-3430. https://doi.org/10.1002/HBM.23249

Cochran, W. G. (1954). The combination of estimates from different experiments. Biometrics, 10(1), 101-129. https://doi.org/10.2307/3001666

Coco, M., Perciavalle, V., Maci, T., Nicoletti, F., di Corrado, D., & Perciavalle, V. (2011). The second-to-fourth digit ratio correlates with the rate of academic performance in medical school students. Molecular Medicine Reports, 4(3), 471-476. https://doi.org/10.3892/MMR.2011.456/HTML

Cohen-Bendahan, C. C. C., van de Beek, C., & Berenbaum, S. A. (2005). Prenatal sex hormone effects on child and adult sex-typed behavior: Methods and findings. Neuroscience & Biobehavioral Reviews, 29(2), 353-384. https://doi.org/10.1016/J.NEUBIOREV.2004.11.004

Crewther, B., Cook, C., Kilduff, L., & Manning, J. (2015). Digit ratio (2D:4D) and salivary testosterone, oestradiol and cortisol levels under challenge: Evidence for prenatal effects on adult endocrine responses. Early Human Development, 91(8), 451-456. https://doi.org/10.1016/j.earlhumdev.2015.04.011

Crewther, B. T., & Cook, C. J. (2019). The digit ratio (2D:4D) relationship with testosterone is moderated by physical training: Evidence of prenatal organizational influences on activational patterns of adult testosterone in physically-active women. Early Human Development, 131, 51-55. https://doi.org/10.1016/j.earlhumdev.2019.02.008

Crewther, B. T., & Cook, C. J. (2020). Medical students preferring a surgical or non-surgical elective differ in their emotional and hormonal responses to a psychological stressor. The American Journal of Surgery, 219(4), 604-607. https://doi.org/10.1016/J.AMJSURG.2019.04.003

de Miranda, K. L., Neyse, L., & Schmidt, U. (2018). Risk preferences and predictions about others: No association with 2d:4d ratio. Frontiers in Behavioral Neuroscience, 12, 9. https://doi.org/10.3389/fnbeh.2018.00009

Elias, M. (1981). Serum cortisol, testosterone, and testosterone-binding globulin responses to competitive fighting in human males. Aggressive Behavior, 7(3), 215-224. https://psycnet.apa.org/record/1982-09292-001

Ernsten, L., Körner, L. M., Schaper, M. L., Lawrenz, J., Richards, G., Heil, M., & Schaal, N. K. (2023). The association of prenatal amniotic sex hormones and digit ratio (2D:4D) in children aged 5 to 70 months: A longitudinal study. PLoS One, 18(3), e0282253. https://doi.org/10.1371/journal.pone.0282253

Escasa, M. J., Casey, J. F., & Gray, P. B. (2010). Salivary testosterone levels in men at a U.S. sex Club. Archives of Sexual Behavior, 40(5), 921-926. https://doi.org/10.1007/S10508-010-9711-3

Falter, C. M., Arroyo, M., & Davis, G. J. (2006). Testosterone: Activation or organization of spatial cognition? Biological Psychology, 73(2), 132-140. https://doi.org/10.1016/J.BIOPSYCHO.2006.01.011

Fink, B., Thanzami, V., Seydel, H., & Manning, J. T. (2006). Digit ratio and hand-grip strength in German and Mizos men: Cross-cultural evidence for an organizing effect of prenatal testosterone on strength. American Journal of Human Biology, 18(6), 776-782. https://doi.org/10.1002/AJHB.20549

Flegr, J., Lindová, J., Pivoñková, V., & Havlíček, J. (2008). Brief communication: Latent toxoplasmosis and salivary testosterone concentration-Important confounding factors in second to fourth digit ratio studies. American Journal of Physical Anthropology, 137(4), 479-484. https://doi.org/10.1002/AJPA.20888

Folland, J. P., Mc Cauley, T. M., Phypers, C., Hanson, B., & Mastana, S. S. (2012). Relationship of 2D:4D finger ratio with muscle strength, testosterone, and androgen receptor CAG repeat genotype. American Journal of Physical Anthropology, 148(1), 81-87. https://doi.org/10.1002/AJPA.22044

Folstad, I., & Karter, A. J. (1992). Parasites, bright males, and the immunocompetence handicap. American Naturalist, 139(3), 603-622. https://doi.org/10.1086/285346

Forstmeier, W. (2011). Women have relatively larger brains than men: A comment on the misuse of general linear models in the study of sexual dimorphism. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 294(11), 1856-1863. https://doi.org/10.1002/AR.21423

Forstmeier, W. (2018). Avoiding misinterpretation of regression lines in allometry: Is sexual dimorphism in digit ratio spurious? BioRxiv, 298786. https://doi.org/10.1101/298786

García-Cruz, E., Huguet, J., Piqueras, M., Ribal, M. J., & Alcaraz, A. (2012). Second to fourth digit ratio, adult testosterone level and testosterone deficiency. BJU International, 109(2), 266-271. https://doi.org/10.1111/J.1464-410X.2011.10249.X

Garn, S. M., Burdi, A. R., Babler, W. J., & Stinson, S. (1975). Early prenatal attainment of adult metacarpal-phalangeal rankings and proportions. American Journal of Physical Anthropology, 43(3), 327-332. https://doi.org/10.1002/ajpa.1330430305

Georgiev, A. V., Ryan, C. P., Gettler, L. T., McDade, T. W., & Kuzawa, C. W. (2017). Second-to-fourth digit ratio (2D:4D) is unrelated to measures of somatic reproductive effort among young men from Cebu, The Philippines. American Journal of Physical Anthropology, 163(3), 437-445. https://doi.org/10.1002/AJPA.23215

Grimbos, T., Dawood, K., Burriss, R. P., Zucker, K. J., & Puts, D. A. (2010). Sexual orientation and the second to fourth finger length ratio: A meta-analysis in men and women. Behavioral Neuroscience, 124(2), 278-287. https://doi.org/10.1037/a0018764

Hedges, L. V., & Olkin, I. (1985). Statistical methods for meta-analysis. Academic Press.

Hickey, M., Doherty, D. A., Hart, R., Norman, R. J., Mattes, E., Atkinson, H. C., & Sloboda, D. M. (2010). Maternal and umbilical cord androgen concentrations do not predict digit ratio (2D:4D) in girls: A prospective cohort study. Psychoneuroendocrinology, 35(8), 1235-1244. https://doi.org/10.1016/J.PSYNEUEN.2010.02.013

Higgins, J. P. T., & Thompson, S. G. (2002). Quantifying heterogeneity in a meta-analysis. Statistics in Medicine, 21(11), 1539-1558. https://doi.org/10.1002/SIM.1186

Hollier, L. P., Keelan, J. A., Jamnadass, E. S. L., Maybery, M. T., Hickey, M., & Whitehouse, A. J. O. (2015). Adult digit ratio (2D:4D) is not related to umbilical cord androgen or estrogen concentrations, their ratios or net bioactivity. Early Human Development, 91(2), 111-117. https://doi.org/10.1016/J.EARLHUMDEV.2014.12.011

Hönekopp, J., Bartholdt, L., Beier, L., & Liebert, A. (2007). Second to fourth digit length ratio (2D:4D) and adult sex hormone levels: New data and a meta-analytic review. Psychoneuroendocrinology, 32(4), 313-321. https://doi.org/10.1016/J.PSYNEUEN.2007.01.007

Hönekopp, J., & Schuster, M. (2010). A meta-analysis on 2D:4D and athletic prowess: Substantial relationships but neither hand out-predicts the other. Personality and Individual Differences, 48(1), 4-10. https://doi.org/10.1016/J.PAID.2009.08.009

Hönekopp, J., & Watson, S. (2010). Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand. American Journal of Human Biology, 22(5), 619-630. https://doi.org/10.1002/AJHB.21054

Hönekopp, J., & Watson, S. (2011). Meta-analysis of the relationship between digit-ratio 2D:4D and aggression. Personality and Individual Differences, 51(4), 381-386. https://doi.org/10.1016/J.PAID.2010.05.003

Hughes, I. A., Davies, J. D., Bunch, T. I., Pasterski, V., Mastroyannopoulou, K., & MacDougall, J. (2012). Androgen insensitivity syndrome. Lancet, 380(9851), 1419-1428. https://doi.org/10.1016/S0140-6736(12)60071-3

Kallai, J., Csathó, Á., Kövér, F., Makány, T., Nemes, J., Horváth, K., Kovács, N., Manning, J. T., Nadel, L., & Nagy, F. (2005). MRI-assessed volume of left and right hippocampi in females correlates with the relative length of the second and fourth fingers (the 2D:4D ratio). Psychiatry Research-Neuroimaging, 140(2), 199-210. https://doi.org/10.1016/j.pscychresns.2004.05.010

Kempel, P., Gohlke, B., Klempau, J., Zinsberger, P., Reuter, M., & Hennig, J. (2005). Second-to-fourth digit length, testosterone and spatial ability. Intelligence, 33(3), 215-230. https://doi.org/10.1016/J.INTELL.2004.11.004

Kilduff, L., Cook, C. J., Bennett, M., Crewther, B., Bracken, R. M., & Manning, J. T. (2013). Right-left digit ratio (2D:4D) predicts free testosterone levels associated with a physical challenge. Journal of Sports Sciences, 31(6), 677-683. https://doi.org/10.1080/02640414.2012.747690

Kilduff, L. P., Hopp, R. N., Cook, C. J., Crewther, B. T., & Manning, J. T. (2013). Digit ratio (2D:4D), aggression, and testosterone in men exposed to an aggressive video stimulus. Evolutionary Psychology, 11(5), 953-964. https://doi.org/10.1177/147470491301100502

Kilmer, J. T., & Rodríguez, R. L. (2017). Ordinary least squares regression is indicated for studies of allometry. Journal of Evolutionary Biology, 30(1), 4-12. https://doi.org/10.1111/JEB.12986

Klimek, M., Galbarczyk, A., Nenko, I., Alvarado, L. C., & Jasienska, G. (2014). Digit ratio (2D:4D) as an indicator of body size, testosterone concentration and number of children in human males. Annals of Human Biology, 41(6), 518-523. https://doi.org/10.3109/03014460.2014.902993

Klimek, M., Galbarczyk, A., Nenko, I., & Jasienska, G. (2016). Women with more feminine digit ratio (2D:4D) have higher reproductive success. American Journal of Physical Anthropology, 160(3), 549-553. https://doi.org/10.1002/AJPA.22989

Knowles, K. (2018). 2D:4D ratio and its relation to spatial awareness, competitiveness and aggression in contact and non-contact sports. Queen Margaret University https://test-eresearch.qmu.ac.uk/handle/20.500.12289/9293

Konstantopoulos, S. (2008). An introduction to meta-analysis. In J. W. Osborne (Ed.), Best practices in quantitative methods (pp. 177-194). Sage.

Kowal, M., Sorokowski, P., Żelaźniewicz, A., Nowak, J., Orzechowski, S., Żurek, G., Żurek, A., Juszkiewicz, A., Wojtycka, L., Sieniuć, W., Poniatowska, M., Tarnowska, K., Kowalska, K., Drabik, K., Łukaszek, P., Krawczyk, K., Stefaniak, T., & Danek, N. (2020). No relationship between the digit ratios (2D:4D) and salivary testosterone change: Study on men under an acute exercise. Scientific Reports, 10(1), 10068. https://doi.org/10.1038/s41598-020-66915-9

Králík, M., Ingrová, P., Kozieł, S., Hupková, A., & Klíma, O. (2017). Overall trends vs. individual trajectories in the second-to-fourth digit (2D:4D) and metacarpal (2M:4M) ratios during puberty and adolescence. American Journal of Physical Anthropology, 162(4), 641-656. https://doi.org/10.1002/AJPA.23153

Kratochvíl, 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(5), 643-646. https://doi.org/10.1098/RSBL.2009.0346

Kratochvíl, L., & Flegr, J. (2017). The mismeasure of (obese) man-Body mass index is an inadequate indicator of body condition. BioRxiv, 149088. https://doi.org/10.1101/149088

Kubranská, A., Lakatošová, S., Schmidtová, E., Durdiaková, J., Celec, P., & Ostatníková, D. (2014). Spatial abilities are not related to testosterone levels and variation in the androgen receptor in healthy young men. General Physiology and Biophysics, 33(3), 311-319. https://doi.org/10.4149/GPB_2014005

Leslie, M. (2019). The mismeasure of hands?: Some researchers say a simple ratio of finger lengths can predict personality and health. Others say that's wishful thinking. Science, 364(6444), 923-925. https://doi.org/10.1126/SCIENCE.364.6444.923

Lolli, L., Batterham, A. M., Kratochvíl, L., Flegr, J., Weston, K. L., & Atkinson, G. (2017). A comprehensive allometric analysis of 2nd digit length to 4th digit length in humans. Proceedings of the Royal Society B: Biological Sciences, 284(1857), 20170356. https://doi.org/10.1098/rspb.2017.0356

Lujan, M. E., Bloski, T. G., Chizen, D. R., Lehotay, D. C., & Pierson, R. A. (2010). Digit ratios do not serve as anatomical evidence of prenatal androgen exposure in clinical phenotypes of polycystic ovary syndrome. Human Reproduction, 25(1), 204-211. https://doi.org/10.1093/humrep/dep363

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. https://doi.org/10.1016/J.EARLHUMDEV.2003.12.002

Maestripieri, D., M. Baran, N., Sapienza, P., & Zingales, L. (2010). Between-and within-sex variation in hormonal responses to psychological stress in a large sample of college students. Stress, 13(5), 413-424. https://doi.org/10.3109/10253891003681137

Malik, A., & Malik, S. (2012). Digit ratio (2D:4D): An indicator of serum testosterone and prenatal programming of specific sports. International Journal of Sports Sciences & Fitness, 1(1), 39-48. https://doi.org/10.5897/JPESM11.008

Malkin, C. J., Pugh, P. J., West, J. N., van Beek, E. J. R., Jones, T. H., & Channer, K. S. (2006). Testosterone therapy in men with moderate severity heart failure: A double-blind randomized placebo controlled trial. European Heart Journal, 27(1), 57-64. https://doi.org/10.1093/EURHEARTJ/EHI443

Manning, J. T. (2011). Resolving the role of prenatal sex steroids in the development of digit ratio. Proceedings of the National Academy of Sciences of the United States of America, 108(39), 16143-16144. https://doi.org/10.1073/PNAS.1113312108

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(6), 399-405. https://doi.org/10.1016/S1090-5138(03)00052-7

Manning, J. T., Churchill, A. J. G., & Peters, M. (2007). The effects of sex, ethnicity, and sexual orientation on self-measured digit ratio (2D:4D). Archives of Sexual Behavior, 36(2), 223-233. https://doi.org/10.1007/S10508-007-9171-6

Manning, J. T., & Fink, B. (2018). Sexual dimorphism in the ontogeny of second (2D) and fourth (4D) digit lengths, and digit ratio (2D:4D). American Journal of Human Biology, 30(4), e23138. https://doi.org/10.1002/AJHB.23138

Manning, J. T., Kilduff, L., Cook, C., Crewther, B., & Fink, B. (2014). Digit ratio (2D:4D): A biomarker for prenatal sex steroids and adult sex steroids in challenge situations. Frontiers in Endocrinology, 5, 9. https://doi.org/10.3389/fendo.2014.00009

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 oestrogen. Human Reproduction, 13(11), 3000-3004. https://doi.org/10.1093/HUMREP/13.11.3000

Manning, J. T., Wood, S., Vang, E., Walton, J., Bundred, P. E., van Heyningen, C., & Lewis-Jones, D. I. (2004). Second to fourth digit ratio (2D: 4D) and testosterone in men. Asian Journal of Andrology, 6(3), 211-215. http://www.asiaandro.com/Abstract.asp?id=876

McIntyre, M. H., Ellison, P. T., Lieberman, D. E., Demerath, E., & Towne, B. (2005). The development of sex differences in digital formula from infancy in the Fels longitudinal study. Proceedings of the Royal Society B: Biological Sciences, 272(1571), 1473-1479. https://doi.org/10.1098/RSPB.2005.3100

Mehdizadeh, R., Noori Sarhozaki, N., & Abbasi, S. (2013). Relationship between second to fourth digit ratio (2D: 4D) and dynamic muscular endurance in trained girl students. International Journal of Sport Studies, 3(1), 99-104.

Millet, K., & Dewitte, S. (2006). Second to fourth digit ratio and cooperative behavior. Biological Psychology, 71(1), 111-115. https://doi.org/10.1016/J.BIOPSYCHO.2005.06.001

Millet, K., & Dewitte, S. (2009). The presence of aggression cues inverts the relation between digit ratio (2D:4D) and prosocial behaviour in a dictator game. British Journal of Psychology, 100(1), 151-162. https://doi.org/10.1348/000712608X324359

Mitsui, T., Araki, A., Imai, A., Sato, S., Miyashita, C., Ito, S., Sasaki, S., Kitta, T., Moriya, K., Cho, K., Morioka, K., Kishi, R., & Nonomura, K. (2015). Effects of prenatal Leydig cell function on the ratio of the second to fourth digit lengths in school-aged children. PLoS One, 10(3), e0120636. https://doi.org/10.1371/JOURNAL.PONE.0120636

Montag, C., Bleek, B., Breuer, S., Prüss, H., Richardt, K., Cook, S., & Reuter, M. (2015). Prenatal testosterone and stuttering. Early Human Development, 91(1), 43-46. https://doi.org/10.1016/j.earlhumdev.2014.11.003

Muller, D. C., Giles, G. G., Bassett, J., Morris, H. A., Manning, J. T., Hopper, J. L., English, D. R., & Severi, G. (2011). Second to fourth digit ratio (2D:4D) and concentrations of circulating sex hormones in adulthood. Reproductive Biology and Endocrinology, 9(1), 1-11. https://doi.org/10.1186/1477-7827-9-57/

Neave, N., Laing, S., Fink, B., & Manning, J. T. (2003). Second to fourth digit ratio, testosterone and perceived male dominance. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1529), 2167-2172. https://doi.org/10.1098/RSPB.2003.2502

Nye, J. V., Bryukhanov, M., Kochergina, E., Orel, E., Polyachenko, S., & Yudkevich, M. (2017). The effects of prenatal testosterone on wages: Evidence from Russia. Economics & Human Biology, 24, 43-60. https://doi.org/10.1016/j.ehb.2016.11.003

Oh, J. K., Kim, K. T., Yoon, S. J., Kim, S. W., & Kim, T. B. (2014). Second to fourth digit ratio: A predictor of adult testicular volume. Andrology, 2(6), 862-867. https://doi.org/10.1111/J.2047-2927.2014.00256.X

Orwin, R. G. (1983). A fail-safe N for effect size in meta-analysis. Journal of Educational Statistics, 8(2), 157-159. https://doi.org/10.3102/10769986008002157

Özen, G., Atar, Ö., & Koç, H. (2019). Digit ratio (2D:4D): Relationship with freestyle swimming performance of adolescent well-trained swimmers. Pedagogics, Psychology, Medical-Biological Problems of Physical Training and Sports, 23(3), 150-154. https://doi.org/10.15561/18189172.2019.0307

Packard, G. C., & Boardman, T. J. (1988). The misuse of ratios, indices, and percentages in ecophysiological research. Physiological Zoology, 61(1), 1-9. https://doi.org/10.1086/physzool.61.1.30163730

Perciavalle, V., di Corrado, D., Petralia, M. C., Gurrisi, L., Massimino, S., & Coco, M. (2012). The second-to-fourth digit ratio correlates with aggressive behavior in professional soccer players. Molecular Medicine Reports, 7(6), 1733-1738. https://doi.org/10.3892/MMR.2013.1426/HTML

Popova, L. D., Vasil'yeva, I. M., & Nakonechna, O. A. (2018). Correlations of aggressiveness with the levels of sex hormones in young men; validity of a proposed anthropometric marker. Neurophysiology, 50(3), 173-182. https://doi.org/10.1007/s11062-018-9734-2

Pustejovsky, J. (2022). clubSandwich: Cluster-Robust (Sandwich) Variance Estimators with Small-Sample Corrections. R Package Version 0.5.7. https://cran.r-project.org/package=clubSandwich

Putz, D. A., Gaulin, S. J. C., Sporter, R. J., & McBurney, D. H. (2004). Sex hormones and finger length: What does 2D:4D indicate? Evolution and Human Behavior, 25(3), 182-199. https://doi.org/10.1016/J.EVOLHUMBEHAV.2004.03.005

Ribeiro, E., Neave, N., Morais, R. N., Kilduff, L., Taylor, S. R., Butovskaya, M., Fink, B., & Manning, J. T. (2016). Digit ratio (2D:4D), testosterone, cortisol, aggression, personality and hand-grip strength: Evidence for prenatal effects on strength. Early Human Development, 100, 21-25. https://doi.org/10.1016/J.EARLHUMDEV.2016.04.003

Ribeiro, E., Neave, N., Morais, R. N., & Manning, J. T. (2016). Direct versus indirect measurement of digit ratio (2D: 4D) a critical review of the literature and new data. Evolutionary Psychology, 14(1), 1474704916632536. https://doi.org/10.1177/1474704916632536

Richards, G. (2017). What is the evidence for a link between digit ratio (2D:4D) and direct measures of prenatal sex hormones? Early Human Development, 113, 71-72. https://doi.org/10.1016/j.earlhumdev.2017.08.003

Richards, G. (2019). Some questions about the replicability and practical applications of digit ratio (2D:4D) research. Science, 364, 923-925. https://doi.org/10.1126/science.364.6444.923

Richards, G., Aydin, E., Tsompanidis, A., Padaigaitė, E., Austin, T., Allison, C., … Baron-Cohen, S. (2022). Digit ratio (2D: 4D) and maternal testosterone-to-estradiol ratio measured in early pregnancy. Scientific Reports, 12(1), 13586. https://doi.org/10.1038/s41598-022-17247-3

Richards, G., Browne, W. V., Aydin, E., Constantinescu, M., Nave, G., Kim, M. S., & Watson, S. J. (2020). Digit ratio (2D: 4D) and congenital adrenal hyperplasia (CAH): Systematic literature review and meta-analysis. Hormones and Behavior, 126, 104867. https://doi.org/10.1016/j.yhbeh.2020.104867

Richards, G., Browne, W. V., & Constantinescu, M. (2021). Digit ratio (2D:4D) and amniotic testosterone and estradiol: An attempted replication of Lutchmaya et al. (2004). Journal of Developmental Origins of Health and Disease, 12(6), 859-864. https://doi.org/10.1017/S2040174420001294

Richards, G., Klimek, M., Jasienska, G., & Marcinkowska, U. M. (2018). Digit ratio (2D:4D) and circulating testosterone, oestradiol, and progesterone levels across the menstrual cycle. Early Human Development, 117, 68-73. https://doi.org/10.1016/J.EARLHUMDEV.2017.12.006

Richards, G., Medland, S. E., & Beaton, A. A. (2021). Digit ratio (2D:4D) and handedness: A meta-analysis of the available literature. Laterality: Asymmetries of Brain, Behaviour, and Cognition, 26(4), 421-484. https://doi.org/10.1080/1357650X.2020.1862141

Riley, R. D., Higgins, J. P. T., & Deeks, J. J. (2011). Interpretation of random effects meta-analyses. BMJ, 342(7804), 964-967. https://doi.org/10.1136/BMJ.D549

Rodeck, C. H., Gill, D., Rosenberg, D. A., & Collins, W. P. (1985). Testosterone levels in midtrimester maternal and fetal plasma and amniotic fluid. Prenatal Diagnosis, 5(3), 175-181. https://doi.org/10.1002/pd.1970050303

Ronay, R., van der Meij, L., Oostrom, J. K., & Pollet, T. v. (2018). No evidence for a relationship between hair testosterone concentrations and 2d:4d ratio or risk taking. Frontiers in Behavioral Neuroscience, 12, 30. https://doi.org/10.3389/FNBEH.2018.00030/BIBTEX

Roney, J. R., & Maestripieri, D. (2004). Relative digit lengths predict men's behavior and attractiveness during social interactions with women. Human Nature, 15(3), 271-282. https://doi.org/10.1007/s12110-004-1009-5

Rosenberg, M. S. (2005). The file-drawer problem revisited: A general weighted method for calculating fail-safe numbers in meta-analysis. Evolution, 59(2), 464-468. https://doi.org/10.1111/j.0014-3820.2005.tb01004.x

Salmon, C. (2015). The impact of prenatal testosterone on female interest in slash fiction. Evolutionary Behavioral Sciences, 9(3), 161-169. https://doi.org/10.1037/ebs0000051

Shingleton, A. W. (2019). Which line to follow? The utility of different line-fitting methods to capture the mechanism of morphological scaling. Integrative and Comparative Biology, 59(5), 1399-1410. https://doi.org/10.1093/icb/icz059

Siegmann, E. M., Bouna-Pyrrou, P., Lenz, B., & Kornhuber, J. (2019). Digit ratio (2D:4D) in relation to substance and computer use: A meta-analysis. Journal of Neural Transmission, 126(5), 623-636. https://doi.org/10.1007/S00702-019-02002-2

Sorokowski, P., Sorokowska, A., Danel, D., Mberira, M. L., & Pokrywka, L. (2012). The second to fourth digit ratio and age at first marriage in semi-nomadic people from Namibia. Archives of Sexual Behavior, 41(3), 703-710. https://doi.org/10.1007/S10508-011-9866-6

Speiser, P. W., & White, P. C. (2003). Congenital adrenal hyperplasia. New England Journal of Medicine, 349(8), 776-788.

Sterne, J. A. C., & Egger, M. (2005). Regression methods to detect publication and other bias in meta-analysis. In H. R. Rothstein, A. J. Sutton, & M. Borenstein (Eds.), Publication bias in meta-analysis: Prevention, assessment and adjustment (pp. 99-110). Wiley.

Tan, Ü. (2008). Ratio of fourth to second fingertip extensions in relation to serum estradiol and testosterone levels in men and women. Perceptual and Motor Skills, 107(1), 3-13. https://doi.org/10.2466/PMS.107.1.3-13

Tanner, J. M. (1990). Foetus into man: Physical growth from conception to maturity. Harvard University Press.

Trivers, R., Manning, J. T., & Jacobson, A. (2006). A longitudinal study of digit ratio (2D:4D) and other finger ratios in Jamaican children. Hormones and Behavior, 49(2), 150-156. https://doi.org/10.1016/J.YHBEH.2005.05.023

Trost, L. W., & Mulhall, J. P. (2016). Challenges in testosterone measurement, data interpretation, and methodological appraisal of interventional trials. The Journal of Sexual Medicine, 13(7), 1029-1046. https://doi.org/10.1016/j.jsxm.2016.04.068

Turanovic, J. J., Pratt, T. C., & Piquero, A. R. (2017). Exposure to fetal testosterone, aggression, and violent behavior: A meta-analysis of the 2D:4D digit ratio. Aggression and Violent Behavior, 33, 51-61. https://doi.org/10.1016/J.AVB.2017.01.008

Unal, M., Urun Unal, G., Balevi, S., Tol, H., & Uyar, M. (2015). The second to fourth digit ratio in acne vulgaris. Pediatric Dermatology, 32(5), 651-655. https://doi.org/10.1111/PDE.12594

van Anders, S. M. (2007). Grip strength and digit ratios are not correlated in women. American Journal of Human Biology, 19(3), 437-439. https://doi.org/10.1002/AJHB.20634

Van Hemmen, J., Cohen-Kettenis, P. T., Steensma, T. D., Veltman, D. J., & Bakker, J. (2017). Do sex differences in CEOAEs and 2D: 4D ratios reflect androgen exposure? A study in women with complete androgen insensitivity syndrome. Biology of Sex Differences, 8(1), 1-10. https://doi.org/10.1186/s13293-017-0132-z

van Leeuwen, B., Smeets, P., Bovet, J., Nave, G., Stieglitz, J., & Whitehouse, A. (2020). Do sex hormones at birth predict later-life economic preferences? Evidence from a pregnancy birth cohort study. Proceedings of the Royal Society B, 287(1941), 20201756. https://doi.org/10.1098/RSPB.2020.1756

Ventura, T., Gomes, M. C., Pita, A., Neto, M. T., & Taylor, A. (2013). Digit ratio (2D:4D) in newborns: Influences of prenatal testosterone and maternal environment. Early Human Development, 89(2), 107-112. https://doi.org/10.1016/J.EARLHUMDEV.2012.08.009

Viechtbauer, W. (2005). Bias and efficiency of meta-analytic variance estimators in the random-effects model. Journal of Educational and Behavioral Statistics, 30(3), 261-293. https://doi.org/10.3102/10769986030003261

Viechtbauer, W. (2010). Conducting meta-analyses in R with the metafor package. Journal of Statistical Software, 36(3), 1-48. https://doi.org/10.18637/JSS.V036.I03

Vigil, P., del Río, J. P., Carrera, B., Ara'nguiz, F. C., Rioseco, H., & Cortés, M. E. (2016). Influence of sex steroid hormones on the adolescent brain and behavior: An update. Linacre Quarterly, 83(3), 308-329. https://doi.org/10.1080/00243639.2016.1211863

Voracek, M., & Loibl, L. M. (2009). Scientometric analysis and bibliography of digit ratio (2D:4D) research, 1998-2008. Psychological Reports, 104(3), 922-956. https://doi.org/10.2466/PR0.104.3.922-956

Voracek, M., & Stieger, S. (2009). Replicated nil associations of digit ratio (2D: 4D) and absolute finger lengths with implicit and explicit measures of aggression. Psicothema, 21(3), 382-389. https://www.redalyc.org/pdf/727/72711821007.pdf

Wallen, K. (2009). Does finger fat produce sex differences in second to fourth digit ratios? Endocrinology, 150(11), 4819-4822. https://doi.org/10.1210/en.2009-0986

Whitehouse, A. J. O., Gilani, S. Z., Shafait, F., Mian, A., Tan, D. W., Maybery, M. T., Keelan, J. A., Hart, R., Handelsman, D. J., Goonawardene, M., & Eastwood, P. (2015). Prenatal testosterone exposure is related to sexually dimorphic facial morphology in adulthood. Proceedings of the Royal Society B: Biological Sciences, 282(1816), 20151351. https://doi.org/10.1098/RSPB.2015.1351

Yang, C.-F. J., Gray, P. B., Zhang, J., & Pope, H. G. (2009). Second to fourth digit ratios, sex differences, and behavior in Chinese men and women. Social Neuroscience, 4(1), 49-59. https://doi.org/10.1080/17470910801942876

Zhang, K., Yang, X., Zhang, M., Wang, C., Fang, P., Xue, M., Zhao, J., Gao, X., Pan, R., & Gong, P. (2020). Revisiting the relationships of 2D:4D with androgen receptor (AR) gene and current testosterone levels: Replication study and meta-analyses. Journal of Neuroscience Research, 98(2), 353-370. https://doi.org/10.1002/JNR.24502

Zirkin, B. R., & Papadopoulos, V. (2018). Leydig cells: Formation, function, and regulation. Biology of Reproduction, 99(1), 101-111. https://doi.org/10.1093/biolre/ioy059

Zitzmann, M., & Nieschlag, E. (2003). The CAG repeat polymorphism within the androgen receptor gene and maleness 1. International Journal of Andrology, 26(2), 76-83. https://doi.org/10.1046/j.1365-2605.2003.00393.x