Stone, C. P. (1935). Sex difference in the running ability of thoroughbred horses. Journal of Comparative Psychology, 19(1), 59-67.
http://dx.doi.org/10.1037/h0061600
After analyzing published reports on thoroughbred running horses, the author concludes that "Many lines of evidence, some of which are weak when considered alone but acquire strength when aligned with others, support the belief that male thoroughbred horses, as a class, surpass female thoroughbreds in running ability. Also, the best of the females are inferior to the best of the males in running ability." (PsycINFO Database Record (c) 2016 APA, all rights reserved)