Direct versus indirect measurement of digit ratio: New data from Austria and a critical consideration of clarity of report in 2D:4D studies

Abstract

Background: Digit ratio (2D:4D), has been the subject of many studies. However, the best method of measuring digit length, either directly (d2D:4D) or indirectly (i2D:4D), is controversial. In many reports i2D:4D has been found to show a directional effect such that d2D:4D > i2D:4D. The exception is three studies from one group of researchers in Austria. Thus, it is unclear whether this effect is nation- or lab-specific.

Aims: To examine evidence for effects of direct versus indirect measurements of mean 2D:4D in Austrians.

Study design: We compared 2D:4D based on direct and indirect measurements of digit lengths of Austrians.

Subjects: There were 80 participants, 21 adults and 59 children.

Outcome measures: 2D:4D of right and left hands, measured directly (from the palm) and indirectly (from hand scans).

Results: Repeatability was high for both d2D:4D and i2D:4D, with the latter slightly higher than the former. d2D:4D and i2D:4D correlated strongly and the sex difference in 2D:4D (males < females) was greater for i2D:4D. With regard to directional differences, we found d2D:4D > i2D:4D for both right (d = -0.53) and left hands (d = -0.80).

Conclusion: There was no evidence of an "Austrian" effect on direct versus indirect measurements of 2D:4D, i.e. mean d2D:4D was greater than i2D:4D. We discuss our findings in the light of issues regarding "clarity of report" from earlier Austrian studies.

Keywords: 2D:4D; Austria; Digit ratio; Direct; Indirect; Measurement.