Result: You don’t develop a preference for the smell of a fertile female over the smell of an infertile female or even of another male. It requires a sexy (i.e., copulatory) experience to teach the male rat’s brain that a female in estrus is “sexually relevant.” The instinct to attempt copulation is there, and he’ll attempt copulation with everybody—but if he doesn’t have the experience, he can’t learn how to turn that instinct into successful action.
