The second to fourth digit ratio (2D:4D) indicates androgen exposure
during early development. Numerous methods are used in the assessment of
2D:4D, however, some are not reliable enough and others are difficult to
perform in large epidemiological studies. We assessed the reliability of
2D:4D using a direct method with a caliper, and compared it with a
computer-assisted analysis on scanned images. Both methods were
moderately correlated, but the scan method produced slightly lower
2D:4D. The main source of variation was differences between subjects
(real variation). Reliability was higher among men and among younger
participants. All reliability coefficients were higher than 0.8 when
three repeated measurements were averaged. Our results suggest that
reliability is influenced by participants’ characteristics. Digit ratios
determined directly with calipers are reliable when repeated
measurements are averaged. (c) 2013 Elsevier Ltd. All rights reserved
