The ratio of second and fourth finger lengths (2D:4D) can determine handedness

Abstract

Objective: The human body exhibits both structural and functional asymmetry. One measure of this asymmetry is the ratio of 2D:4D, which is the proportion of measurements of the 2nd (2D) and 4th finger (4D). In this research, our objective is to investigate the potential association between the ratio of 2D:4D and handedness with voluntary individuals. Methods: A total of 312 individuals volunteered to take part in the research, where their left and right hand's 4th and 2nd finger lengths were measured using a precise digital caliper. The "Edinburgh Handedness Inventory" was used to determine hand lateralization. To determine the significance between the two independent groups, the Mann Whitney U Test was used. On the other hand, to determine the significance between the two dependent groups, the Wilcoxon Signed Rank Test was utilized. Results: Of the participants, 154 were male and 158 were female (age range 18-55, mean age=28.34). According to the Edinburgh Handedness Inventory, 275 individuals were right handed, 18 were left handed, and 19 were bimanual. The Mann Whitney U Test showed a significant result in the ratio of right hand 2D:4D between male and female participants who were right handed (z =-1.979, p = 0.048). Additionally, the Wilcoxon Signed Ranks Test demonstrated a difference between the right and the left hand ratio of 2D:4D for all participants which was significant (z = -2.822, p = 0.005), as well as for participants who were right handed (z = -2.850, p = 0.004). Conclusion: The ratio of 2D:4D finger lengths could be a significant indicator of hand preference in both male and female healthy individuals. The ratio of 2D:4D holds potential as an indicator and research tool in understanding human emotions, thoughts, and behaviors.

Keywords

• Finger
• Handedness
• Finger Length Ratio
• Testosterone
• Estrogen

References

1. 1.Manning J, Kilduff L, Cook C, Crewther B, Fink B. DigitRatio (2d:4d): a Biomarker For Prenatal Sex Steroids AndAdult Sex Steroids In Challenge Situations. FrontEndocrinol (Lausanne). 2014;5:9.doi:10.3389/fendo.2014.00009
2. 2.Hönekopp J, Watson S. Meta-analysis of digit ratio2D:4D shows greater sex difference in the right hand. AmJ Hum Biol. 2010;22(5):619-30. doi:10.1002/ajhb.21054
3. 3.Manning JT, Scutt D, Wilson J, Lewis-Jones DI. The ratioof 2nd to 4th digit length: a predictor of sperm numbersand concentrations of testosterone, luteinizing hormoneand oestrogen. Hum Reprod. 1998;13(11):3000-4.doi:10.1093/humrep/13.11.3000
4. 4.McIntosh A, Duffy D, Wright M, et al. Genetic InfluencesOn Handedness: Data From 25,732 Australian and DutchTwin Families. Neuropsychologia 2009;47(2):330-7.doi:10.1016/j.neuropsychologia.2008.09.005
5. 5.Armour JA, Davison A, McManus IC. Genome-wideassociation study of handedness excludes simple geneticmodels. Heredity (Edinb). 2014;112(3):221-5.doi:10.1038/hdy.2013.93
6. 6. De Kovel CG, Carrion-Castillo A, Francks C. A large-scalepopulation study of early life factors influencing left-handedness. Sci Rep. 2019;9(1):584.doi:10.1016/j.bandc.2006.04.005
7. 7.Ooki S. Genetic and Environmental Influences on theHandedness and Footedness in Japanese Twin Children.Twin Research and Human Genetics. 2005;8(6):649-56.doi:10.1375/183242705774860222
8. 8.Ooki S. Nongenetic factors associated with humanhandedness and footedness in Japanese twin children. Environ Health Prev Med. 2006;11(6):304-12. doi:10.1007/BF02898021

9. 9.Cohen-Bendahan CC, Buitelaar JK, van Goozen SH,Cohen-Kettenis PT. Prenatal exposure to testosterone andfunctional cerebral lateralization: a study in same-sex andopposite-sex twin girls. Psychoneuroendocrinology.2004;29(7):911-6. doi:10.1016/j.psyneuen.2003.07.001
10. 10.Grimshaw GM, Bryden MP, Finegan J. Relationsbetween prenatal testosterone and cerebral lateralizationin children. Neuropsychology 1995;9(1):68-79.doi:10.1037/0894-4105.9.1.68
11. 11.McManus IC, Bryden MP. Geschwind's theory ofcerebral lateralization: developing a formal, causal model. Psychol Bull. 1991;110(2):237-53. doi:10.1037/0033-2909.110.2.237
12. 12.Manning JT, Fink B. Digit ratio (2D:4D) and itsrelationship to foetal and maternal sex steroids: A mini-review. Early Hum Dev. 2023;183:105799.doi:10.1016/j.earlhumdev.2023.105799
13. 13.Manning JT, Fink B. Digit ratio (2D:4D), dominance,reproductive success, asymmetry, and sociosexuality inthe BBC Internet Study. Am J Hum Biol. 2008;20(4):451-61.doi:10.1002/ajhb.20767
14. 14.Aksu F, Tatar A, Türkmen S, Çelikli S, Çelik A, Tetik S.Paramediklerde Psikolojik Değerlendirme Ve Eldeki 2/4Parmak Oranının Kişilik Yapısı İle İlişkisi. DEÜ TıpFakültesi Dergisi. 2010;24(1):11-8.
15. 15.Akdeniz G. Evaluation of relationship between digitratio (2D: 4D) and epilepsy: Can 2D:4D be a clue forepileptogenesis?. Journal of Clinical and ExperimentalInvestigations. 2018;9(2):87-90.doi:10.5799/jcei.433812
16. 16.Bruin EI, Nijs PF, Verheij F, Verhagen DH, FerdinandRF. Autistic features in girls from a psychiatric sample arestrongly associated with a low 2D:4D ratio. Autism.2009;13(5):511-21. doi:10.1177/1362361309335720
17. 17.Manning JT, Baron-Cohen S, Wheelwright S, SandersG.The 2nd to 4th digit ratio and autism. Dev Med ChildNeurol. 2001;43(3):160-4. doi:10.1111/j.1469-8749.2001.tb00181.x
18. 18.Teatero ML, Netley C. A critical review of the researchon the extreme male brain theory and digit ratio (2D:4D).J Autism Dev Disord. 2013;43(11):2664-76.doi:10.1007/s10803-013-1819-6
19. 19.Demirci EÖ, DB Ö. Dikkat eksikliği ve hiperaktivitebozukluğu olan erkek çocuk ve ergenlerde agresyon,empati ve 2D: 4D parmak oranlarının ilişkisi. Yeni Symp2015:53;2-8. doi:10.5455/NYS.20151221025259
20. 20.Uysal SA, Ekinci Y, Çoban F, Yakut Y. Edinburgh eltercihi anketi Türkçe güvenirliğinin araştırılması. Journalof Exercise Therapy and Rehabilitation. 2019;6(2):112-8.
21. 21.Beaton AA, Rudling N, Kissling C, Taurines R, Thome J.Digit ratio (2D:4D), salivary testosterone, andhandedness. Laterality. 2011;16(2):136-55.doi:10.1080/13576500903410369
22. 22.Ventura T, Gomes MC, Pita A, Neto MT, Taylor A. Digitratio (2D: 4D) in newborns: influences of prenataltestosterone and maternal environment. Early humandevelopment. 2013;89(2):107-12.doi:10.1016/j.earlhumdev.2012.08.009
23. 23. Protopapas HA. The 2D:4D Ratio, Handedness, and Sex Across The Age Span [master's thesis on the Internet].Wilfrid Laurier University Faculty of Science, Departmentof Kinesiology and Physical Education; 2016.
24. 24. Freud S, Brill AA. Three Contributions to the Theory ofSex. Mineola, NY: Dover Publications; 2001.
25. 25.Putz DA, Gaulin SJ, Sporter RJ, McBurney DH. Sexhormones and finger length: What does 2D: 4D indicate?.Evolution and Human Behavior. 2004;25(3):182-99.doi:10.1016/j.evolhumbehav.2004.03.005
26. 26.Malas MA, Dogan S, Evcil EH, Desdicioglu K. Fetaldevelopment of the hand, digits and digit ratio (2D:4D).Early Hum Dev. 2006;82(7):469-75.doi:10.1016/j.earlhumdev.2005.12.002
27. 27. Manning JT. Resolving the role of prenatal sex steroidsin the development of digit ratio. Proc Natl Acad Sci USA.2011;108(39):16143-4.doi:10.1073/pnas.1113312108
28. 28. Cherbuin N, Brinkman C. Hemispheric interactions aredifferent in left-handed individuals. Neuropsychology.2006;20(6):700-7. doi:10.1037/0894-4105.20.6.700
29. 29.Serrien DJ, Ivry RB, Swinnen SP. Dynamics ofhemispheric specialization and integration in the contextof motor control. Nat Rev Neurosci. 2006;7(2):160-6.doi:10.1038/nrn1849
30. 30. Cabinio M, Blasi V, Borroni P, et al. The shape of motorresonance: right- or left-handed? Neuroimage.2010;51(1):313-23.doi:10.1016/j.neuroimage.2010.01.103