When the Love Hormone Leads to Violence

Abstract

Does oxytocin influence intimate partner violence (IPV)? Clues from prior research suggest that oxytocin increases prosocial behavior, but this effect is reversed among people with aggressive tendencies or in situations involving defensive aggression. Animal research also indicates that oxytocin plays a central role in defensive maternal aggression (i.e., protecting pups from intruders). Among highly aggressive people, a boost of oxytocin may cause them to use aggression toward close others as a means of maintaining their relationship. Adopting an interactionist approach, we predicted that oxytocin would increase IPV inclinations, but this effect would be limited to people high in trait physical aggression. In a double-blind, placebo-controlled, between-subject experiment, participants varying in trait physical aggression received either 24 international unit of oxytocin or a placebo. Following two provocation tasks, participants rated the probability that they would engage in various aggressive behaviors (e.g., slapping, throwing an object that could hurt) toward a romantic partner. Oxytocin increased IPV inclinations, but this effect was limited to participants prone to physical aggression. These data offer the first evidence that IPV inclinations have a biological basis in a combination of oxytocin and trait physical aggressiveness.