Editing Digit ratio (section)

==Measurement==
The 2D:4D ratio is calculated by dividing the length of the [[index finger]] by the length of the [[ring finger]] of the same hand. Other digit ratios are also calculated similarly in the same hand.

The digit length is typically measured on the palmar (ventral, "palm-side") hand, from the midpoint of the bottom crease to the tip of the finger.<ref name="Mayhew_2007">{{cite journal | vauthors = Mayhew TM, Gillam L, McDonald R, Ebling FJ | title = Human 2D (index) and 4D (ring) digit lengths: their variation and relationships during the menstrual cycle | journal = Journal of Anatomy | volume = 211 | issue = 5 | pages = 630–638 | date = November 2007 | pmid = 17764524 | pmc = 2375787 | doi = 10.1111/j.1469-7580.2007.00801.x }}</ref> Measurement of the digits on the dorsal ("back-side") hand, from the tip of the finger to the proximal phalange-bone protrusion (which occurs when digits are bent at 90&nbsp;degrees to the palm) has also recently gained acceptance.<ref name="Kumar_2017">{{cite journal | vauthors = Kumar S, Voracek M, Singh M | title = Sexual Dimorphism in Digit Ratios Derived from Dorsal Digit Length among Adults and Children | journal = Frontiers in Endocrinology | volume = 8 | pages = 41 | date = 6 March 2017 | pmid = 28321205 | pmc = 5337486 | doi = 10.3389/fendo.2017.00041 | doi-access = free }}</ref><ref name="Auger_2011">{{cite journal | vauthors = Auger J, Eustache F | title = Second to fourth digit ratios, male genital development and reproductive health: a clinical study among fertile men and testis cancer patients | journal = International Journal of Andrology | volume = 34 | issue = 4 Pt 2 | pages = e49–e58 | date = August 2011 | pmid = 21091719 | doi = 10.1111/j.1365-2605.2010.01124.x | doi-access = free }}</ref> A study has shown that, compared to the palmar digit ratio, the dorsal digit ratio is a better indicator of bone digit ratio.<ref name="Auger_2011"/> Furthermore, the palmar digit ratio is affected by the differential positioning of flexion creases.<ref name="Kumar_2019">{{cite journal | vauthors = Kumar S, Voracek M, Singh M | title = Differential Placing of Flexion Creases Contributes to Sex Differences in the Second-to-Fourth Digit Ratio (2D:4D) | journal = Frontiers in Endocrinology | volume = 10 | pages = 537 | date = 2 August 2019 | pmid = 31428058 | pmc = 6688535 | doi = 10.3389/fendo.2019.00537 | doi-access = free }}</ref>

It has been alleged that, because academics have accepted a variety of techniques and equipment (such as [[calipers]], [[radiography]] and [[Photocopier|photocopy]]), researchers record multiple measurements and report only those which have [[P-Hacking|significant findings]],<ref name="Smoliga_2021">{{cite journal | vauthors = Smoliga JM, Fogaca LK, Siplon JS, Goldburt AA, Jakobs F | title = Giving science the finger-is the second-to-fourth digit ratio (2D:4D) a biomarker of good luck? A cross sectional study | journal = BMJ | volume = 375 | pages = e067849 | date = December 2021 | pmid = 34911738 | pmc = 8672321 | doi = 10.1136/bmj-2021-067849 }}</ref> a form of [[reporting bias]].