How Can Evolutionary Psychology Help Explain Intimate Partner Violence?

Jaimie has been out of town for nearly a week at her annual industry conference. Despite having been together for over a year, her boyfriend, Johnathan, still feels anxious when she is away on business trips. His anxiety has deepened because Jaimie has been “too busy to talk on the phone.” When Jaimie does finally return home, Johnathan ignites an argument, accusing her of spending time with her male co-workers. The argument escalates to shouting, with Johnathan accusing her of cheating on him while away. As Jaimie continues to plead her innocence and faithfulness to Johnathan, he pins her against the wall, with his hand around her neck, as he threatens to strike her if she refuses to admit her infidelity.

At some point in their lifetime, 10 to 35 percent of people experience intimate partner violence. (The numbers vary depending on the sample studied and precise definition of “intimate partner violence.”)

Why is violence among partners so common? Social scientists have proposed several theories, which primarily fall under two umbrellas: sociological explanations, and biological and psychological explanations. (Because the existing literature primarily focuses on violence in heterosexual relationships, my discussion is limited to violence between a man and a woman.)

Perhaps the most well-known sociological explanation is the social learning theory of intimate partner violence. This theory suggests that violence against intimate partners is a learned behavior: Men abuse their wives because they grew up witnessing their fathers abusing their mothers, and women become victims because they observed their mothers being abused. This is known as the “intergenerational cycle of violence.”

Why is intimate partner violence such a pervasive feature of human relationships?

The biological perspective, on the other hand, emphasizes structural and chemical abnormalities in the brain, usually resulting from head injury or trauma, that can make it harder to control impulsive and aggressive behavior. Standard psychological perspectives typically emphasize how individual personality differences contribute to intimate partner violence and victimization.

What each of these perspective lack, however, is an explanation for why violence against intimate partners occurs in the first place. Put differently, why is intimate partner violence such a pervasive feature of human relationships? If we assume the social learning perspective is correct, then we fall into a circular question of who was the first person to perpetrate violence against an intimate partner from which everyone else learned? The purely biological perspective cannot account for individuals with normal brain function who nevertheless perpetuate violence; nor do all perpetrators suffer from a psychological disorder or abuse drugs and alcohol. Certainly, these factors contribute to a large proportion of intimate partner violence. But that still doesn’t explain why intimate partner violence occurs.

Another perspective, an evolutionary psychological perspective, can shed light on this pervasive why.

Evolutionary psychology is an approach to psychology that applies principles of evolutionary biology—evolution by natural selection, for example—to understand the structure and function of the mind (for longer discussions, see here, here, and here). Evolutionary psychology essentially uses evolutionary theory as a framework to understand, explain, and generate hypotheses about psychology and behavior.

Evolutionary psychology is often misunderstood or maligned. Common criticisms, such as the assertion of “just so” storytelling, that evolutionary psychology proposes genetic determinism, or that research findings have aversive political implications. Another misunderstanding—particularly relevant for understanding intimate partner violence—is the naturalistic fallacy. This is the notion that because something is natural then it must be good or acceptable. Applied to intimate partner violence, the naturalistic fallacy might allege that when psychologists propose an evolutionary explanation for intimate partner violence, they implicitly condone the behavior. This is simply untrue. Evolutionary explanations for behavior bear no relation to the moral judgements of that behavior.

The ultimate level of analysis addresses whether violence “works” as an evolved solution to the problem of (actual or imagined) female infidelity.

Unlike the other explanations discussed above, evolutionary psychology can offer possible answers to deep why questions. Evolutionary psychologists do this by explaining intimate partner violence at two levels of analysis: ultimate and proximate. Both levels of analysis explain different features of Jaimie and Johnathan’s scenario. The ultimate level of analysis explains why a trait or behavior we observe could have arisen via natural selection. In other words, what could be the evolved function of, or reason for perpetrating violence against a romantic partner? The ultimate level addresses the why questions. The proximate level of analysis explains the immediate causes of a trait or behavior (how traits and behaviors manifest). In other words, what were the visible causes or situation-specific factors that lead to violence? Sociological, biological, and mainstream psychological explanations discussed above would fall under the proximate level of analysis.

A predominant explanation for why males perpetuate violence is the cuckoldry risk (or sperm competition risk) hypothesis. In short, because fertilization and gestation occur in women, women can be certain that their offspring are genetically their own; men cannot be so certain. A variety of research evidence supports the cuckoldry risk hypothesis: female “double mating” (i.e., women having sex with at least two different men within a short span of time), relative testes size of humans, ejaculate adjustment, and greater interest in copulating with a romantic partner after a period of separation.

The line of research on the cuckoldry risk hypothesis suggests that men have evolved a suite of what are called “anti-cuckoldry” tactics (psychological and behavioral responses) to protect against rearing another man’s children. Female infidelity is argued to be the primary context for which cuckoldry occurred throughout human evolutionary history. Within this level of analysis, physical violence is proposed to be an (albeit extreme) anti-cuckoldry tactic intended to prevent or correct for female infidelity.

The ultimate level of analysis addresses whether violence “works” as an evolved solution to the problem of (actual or imagined) female infidelity. Put differently, if intimate partner violence indeed mitigates the risk of cuckoldry, then intimate partner violence may also be associated with behaviors that increase the man’s probability conceiving with his partner, such as more frequent intercourse with the victim. Recent research in humans does show a positive relationship between frequency of violence perpetration and frequency of sexual intercourse with the victim—a finding that’s mirrored in research with chimpanzees, gorillas, macaques, and baboons.

The evolutionary origins of men’s violence certainly does not mean that all men are or will be abusive. What, then, spurs violence in relationships? This is where the proximate level of analysis comes into play. Jealousy is the most cited proximal cause of intimate partner violence and has a wide range of behavioral consequences in romantic relationships, from heightened vigilance of a partner’s activities to spousal homicide. For men, sexual jealousy in particular most often arises when he suspects or knows that his partner has been sexually unfaithful (because female infidelity directly increases the risk of cuckoldry—though men are often not conscious of this extended reasoning).

But not all men are equally jealous, and men do not all react the same when they feel jealousy. What might explain individual differences in jealous responses? Along with several colleagues, I have studied individual differences in, and consequences of, romantic attachment in relationships. Romantic attachment is the deep, emotional bond (or lack thereof) with a romantic partner that regulates real or imagined threats to a romantic partnership (whether the threats are acute or ongoing).

The evolutionary origins of men’s violence certainly does not mean that all men are or will be abusive.

Attachment bonds are assessed along two dimensions: anxiety and avoidance. Attachment anxiety (or over-activation of the attachment system) predicts chronic jealousy, hypervigilance to cues of rejection or abandonment by a partner, over-perception of ambiguous behaviors by a partner as potentially signaling infidelity, and greater perceived risk of a partner’s infidelity. Attachment anxiety has also been shown to predict a range of negative relationship behaviors, including negative partner-directed behaviors (e.g., emotional manipulation, threats), psychological and physical violence, and sexual coercion. Attachment avoidance (or under-activation of the attachment system), on the other hand, predicts greater self-reliance in relationships. Unlike attachment anxiety, attachment avoidance is unassociated with perceptions of a partner’s infidelity.

The evolutionary perspective may also suggest ways in which intimate partner violence can be prevented. Confronting the underlying, individual-level source of violence—attachment bonds—and understanding why violence is often an outcome of jealousy, may be a particularly effective approach for preventing violence and rehabilitating perpetrators. For at-risk individuals, such as those with high attachment-anxiety, therapeutic interventions may focus on cognitive reframing of anxiety-provoking situations (this is effective for anxiety-related disorders in adults). Attachment dynamics are a ubiquitous feature of human romantic relationships; by identifying individuals exhibiting insecure attachment bonds early, we may be able to reduce partner violence (e.g., physical beatings, partner-rape).

Johnathan’s behavior was an extreme, but not necessarily uncommon, manifestation of our evolved psychology. Individual differences in attachment bonds make jealousy more or less likely in situations where a threat to the relationship is perceived—such as Johnathan’s speculation that Jaimie was spending time with her male co-workers. Physical violence is just one behavioral response to the confluence of individual differences and situation-specific cues. The logical next step (in my research program, at least) is to better understand how attachment bonds develop over the lifespan—explanations for which are currently debated (see here for my perspective).

There is no single explanation for intimate partner violence. But to deny our evolved psychology is to deny ourselves a comprehensive understanding of the problem.