Ejaculation by male rhesus as a function of the female partner

Nine adult male rhesus monkeys were given eight 10-min tests of sexual behavior with eight ovariectomized female rhesus pretreated with estradiol benzoate. Males differed significantly in the number of tests during which they ejaculated, and females differed in the frequency with which specific males ejaculated when tested with them. With phylogenetic increase in neocortex, pair compatibility may be as important as hormonal stimulation in regulating male sexual performance. If this is correct, the problem of understanding the determinants of primate sexual behavior becomes more formidable.