/r/ for rough in Indo-European

A Across the Indo-European language family, the proportion of rough words with /r/ is much higher than the proportion of smooth words with /r/; B Each dot represents a language (size of the circle = number of words); whiskers show 95% Bayesian credible intervals corresponding to the mixed-effects Bayesian logistic regression analysis indicating that rough words have a much higher proportion of /r/ (posterior mean = 63%) than smooth words (posterior mean= 35%).

Winter, B., Sóskuthy, M., Perlman, M., & Dingemanse, M. (2022). Trilled /r/ is associated with roughness, linking sound and touch across spoken languages. Scientific Reports, 12(1), 1035. doi: 10.1038/s41598-021-04311-7 PDF