Sex differences


 * http://www.polymath-systems.com/intel/essayrev/sexdiff.html
 * https://web.stanford.edu/~niederle/NV.AnnualReview.Print.pdf
 * https://www.psychologytoday.com/blog/the-how-and-why-sex-differences/201104/why-dont-women-ask-men-out-first-dates