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Repeatability and interobserver error of digit ratio (2D:4D) measurements made by experts
Author(s) -
Voracek Martin,
Manning John T.,
Dressler Stefan G.
Publication year - 2006
Publication title -
american journal of human biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.559
H-Index - 81
eISSN - 1520-6300
pISSN - 1042-0533
DOI - 10.1002/ajhb.20581
Subject(s) - digit ratio , repeatability , intraclass correlation , replication (statistics) , hum , statistics , reliability (semiconductor) , null hypothesis , numerical digit , population , psychology , correlation , observational error , limits of agreement , testosterone (patch) , demography , audiology , biology , clinical psychology , medicine , mathematics , psychometrics , genetics , arithmetic , sociology , power (physics) , geometry , quantum mechanics , art history , physics , performance art , nuclear medicine , art
The second‐to‐fourth digit ratio (2D:4D) is sexually differentiated (lower in men than in women), a likely biomarker for organizational (permanent) effects of prenatal testosterone, and a correlate of many sex‐dependent, hormonally influenced traits and phenotypes. The extent of 2D:4D measurement repeatability across different research groups is unknown. This study assessed the repeatability and interobserver error of 2D:4D measurements made by 17 experts (researchers who have contributed to the 2D:4D literature). Results indicate that 2D:4D, because it is a ratio variable, is notably less precisely measurable than finger length. Absolute‐agreement intraclass correlation coefficients for these traits are about 0.75 vs. about 0.95, respectively. Associations of 2D:4D with target traits were usually of small size; measurement unreliability attenuates effects. This may explain some null findings and replication failures encountered in 2D:4D research. However, agreement levels are still sufficient to permit conclusions about findings from different research groups. One implication of this is that the marked geographical and population differences in typical 2D:4D levels, as reported in the literature, are veridical, and not due to divergent measurement habits across research groups. Some practical recommendations for 2D:4D measurement are offered. Am. J. Hum. Biol. 19:142–146, 2007. © 2006 Wiley‐Liss, Inc.