Editing Digit ratio (section)

{{Short description|Ratio of lengths of fingers}}
{{for|the observation about the frequencies of leading digits of numbers|Benford's law}}
{{Use dmy dates|date=December 2023}}
[[File:Hand zur Abmessung 2D4D.jpg|thumb|Hand with index finger shorter than the ring finger, resulting in a small 2D:4D ratio.]]
[[File:Hand photograph dorsal1 copy.jpg|thumb|Image shows the measurement procedure of dorsal digit length using [[vernier calipers]]. The hand is placed on the edge of a table so that fingers are rested on table while making an angle of 90&nbsp;degrees to the palm.]]
The '''digit ratio''' is the ratio taken of the lengths of different [[finger|digit]]s or fingers on a [[hand]].

The most commonly studied digit ratio is that of the 2nd ([[index finger]]) and 4th ([[ring finger]]), also referred to as the 2D:4D ratio, measured on the [[Hand|palm]] side. It is proposed that the 2D:4D ratio indicates the degree to which an individual has been exposed to [[androgens]] during key stages of [[fetal]] development. A lower ratio (relatively shorter index finger) has been associated with higher androgen exposure, which would be the physiological norm for males but may also occur in some exceptional circumstances in females. The latter include developmental disorders such as [[congenital adrenal hyperplasia]]. 

The 2D:4D ratio has been postulated to correlate with a range of physical and cognitive traits in childhood and adulthood, including personality traits such as assertiveness in women, aggressiveness in men, and cognitive abilities such as numerical skills.<ref name="Jeevanandam_2016">{{cite journal | vauthors = Jeevanandam S, Muthu PK | title = 2D:4D Ratio and its Implications in Medicine. | journal = Journal of Clinical and Diagnostic Research | volume = 10 | issue = 12 | pages = CM01–CM03 | date = 2016 | pmid = 28208851 | doi = 10.7860/JCDR/2016/21952.9000 | s2cid = | pmc = 5296424 }}</ref> It has also been shown to vary considerably between racial groups<ref name="Manning_2000" /> with males having, on average, lower 2D:4D ratio than females.<ref>{{Cite journal |last1=Nayak |first1=Satheesha B. |last2=Nair |first2=Dhiviah |last3=Ravi |first3=Vimal |last4=Aithal |first4=Ashwini P. |date=2018-09-20 |title=A comparative study on digit ratio and hand patterns of three ethnic races of Malaysia |journal=Egyptian Journal of Forensic Sciences |language=en |volume=8 |issue=1 |pages=56 |doi=10.1186/s41935-018-0087-1 |doi-access=free |issn=2090-5939}}</ref>

Studies in this field have drawn criticism over questionable statistical significance and difficulties in reproducing their findings<ref name="No relationship between the digit r">{{cite journal | vauthors = 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 | display-authors = 6 | title = No relationship between the digit ratios (2D:4D) and salivary testosterone change: Study on men under an acute exercise | journal = Scientific Reports | volume = 10 | issue = 1 | pages = 10068 | date = June 2020 | pmid = 32572079 | pmc = 7308391 | doi = 10.1038/s41598-020-66915-9 | bibcode = 2020NatSR..1010068K }}</ref><ref name="Leslie_2019" /><ref name="Jones_2020" /> as well as lack of high quality research protocols.<ref name="Smoliga_2021" />