OTTAWA — Women are bitchy by nature. No, that’s not a sexist remark. That’s science. Or at least that’s what University of Ottawa psychologist Tracy Vaillancourt more or less concludes in her latest research on “intrasexual competition” among women. Derisive comments on another woman’s appearance, spreading rumours about her sex life, giving her the silent treatment — all this and more reflects the kind of “indirect aggression” women deploy against each other in the competition for a mate, she says in a report published this week in a Royal Society journal. “Human females have a particular proclivity for using indirect...