Diminutive Digits Discern Delicate Details: Fingertip Size and the Sex Difference in Tactile Spatial Acuity

Multivariate Bayesian analysis. Scatterplots and best-fit curves are shown for four models. The data points (participants' GOT thresholds) are identical in the four plots; the models differ in how they consider the data to have been generated. a, Null model: the data derive from a single Gaussian population distribution. b, Sex model: female and male data (left–right offset for clarity) originate from separate (red and blue) Gaussian populations. c, Finger size model: the data derive from a linear trend on fingertip area. d, Finger-size-and-sex model. Women: red □; men: blue ○. Bayes factors (BF) are likelihoods relative to the null model.

Finger surface microstructure. a, Scans from index fingers of a woman (left) and man (right) traced (yellow) for area measurement (scale bar, 1 cm). b, Portions of 2400 dpi scans taken from boxed regions in a after staining (scale bar, 1 mm). Sweat pores (punctate stain) are more densely distributed in the smaller finger. c, Within-ridge (yellow arrow) and between-ridge (green arrow) pore-to-pore measurements were taken from 15 participants. Dots: sweat pores; lines: finger print grooves. d, Pore-to-pore within-ridge distance (top), between-ridge distance (middle), and sweat pore density (lower) versus fingertip surface area. Women: red □; men: blue ○. *correlation p < 0.05.