Tag Archives: evolution

Applying the Evolutionary Science of Attachment Bonds

Attachment theory is one of the most enduring theoretical frameworks in psychology, spanning the areas of developmental psychology, social/personality psychology, and evolutionary psychology. Broadly, classical attachment theory, originally developed by John Bowlby, focuses on the development of attachment bonds between parents and infants, and how those early attachments influence social development throughout childhood and into adolescence, coalescing in adult romantic attachments.

During my doctoral studies I became interested in attachment utilizing an evolutionary framework after reading a classic (monster of a) paper from Dr. Marco Del Giudice. I was fascinated with questions of the functional nature of adult attachments: What purpose did pair-bonding and romantic attachments serve in adults? What was the relationship between romantic attachments and the diversity of sexual strategies in humans? In what ways are romantic attachment similar, and different, from infant attachments?

I began exploring these questions about attachment intensely, and for my comprehensive exams to advance to candidacy I wrote a novel theoretical framework for understanding the evolution and development of attachment systems. I am currently working on refining this framework to publish in a series of papers.

The first of this trilogy, The Nature of Attachment Systems, has just been accepted for publication in Social and Personality Psychology Compass. The primary thesis of this paper is that infant and adult attachments are fundamentally different in nature; that is, their evolutionary history, operation in social contexts, and functions are different. This diverges from classical attachment theory by way of proposing that what we commonly think of as “attachment” is comprised of two distinct evoled cognitive systems, rather than one as proposed by classical interpretations of attachment theory.

One hypothesis that I propose in this paper is the Mate Guarding Hypothesis of attachment, which states:

Once pair-bonding and consequent attachments are established, mate guarding ensures the optimization of resource investment for both males and females. Here, I propose that mate guarding is the primary manifestation of the romantic attachment system, whereby romantic attachment bonds are a primary motivational source underlying mate guarding behaviors. Mate guarding behavior occurs in response to threats to the pair-bonded relationship. Threats can be exogenous in origin (intrasexual competitors), or endogenous in origin (emotional detachment or disinterest of mate). Threats may be acute in nature (a present, intrasexual competitor), ongoing (chronic jealousy), or perceived (suspicion of partner’s activities). Threats to a pair-bonded relationship can thus be operationalized as endogenous or exogenous threats to the stability of the pair-bond that negatively affect optimal investment of resources into the mateship, for either partner. The romantic attachment system, then, is a suite of psychological mechanisms that primarily operate to prevent, correct, and address threats to the pair-bond most often by regulating mate guarding behavior, broadly construed.

Barbaro, in press, pp. 10-11.

This hypothesis follows from a line of empirical work that I have been leading since 2016 on the associations between attachment orientations, particularly anxiety (which is characterized by hyper-activation of the attachment system), and mate guarding outcomes (see here and here).

Essentially, what we understand to be mate guarding behaviors — that have been heavily researched by evolutionary psychologists — are a primary manifestation of the romantic attachment system, which actively monitors threats to one’s pair-bond (see figure). Why is this important? Because pair-bonded relationships are reliant on heavy resource investment from both parties. And, particularly for males, is quite divergent from the classical “promiscuous male” mating strategy that dominates the male mammalian kingdom. There is a reason that pair-bonding is rare among mammals — it’s got to be worth the time (evolutionarily speaking).

Conceptual depiction of the Mate Guarding Hypothesis of Romantic Attachment based on Barbaro, in press.

Okay, so why is any of this important? Because understanding how our mind monitors threats our romantic relationship can help us be more self-aware and understanding of our own (and our partner’s) behaviors within our relationship. Recently, Dr. Michael Bailey asked me to briefly discuss ways in which evolutionary psychology can be applied to our lives. What I shared with him (and his psychology class via video), touches on my recent attachment work, especially with regard to the mate guarding hypothesis. Below is the 12 minute clip (shared with permission).

Although I am obviously biased, I find the notion that your attachment bond and its manifestations within your relationship are strongly influenced, in part, by the relationship dynamics within that relationship context far more appealing than the still popular proposition that your early relationships with your parents set the course for your adult romantic relationships — but that’s a topic for the next paper…

Brief Book Review: Mind in Motion


A goal of mine for 2020 is to write more — a goal many academics commit to each year. This year, however, as I have stepped away from the ivory tower, I am going to make a concerted effort to write more public essays and blog posts now that I am far less tied to the necessity of formal academic publishing. As part of this goal, I am introducing a new series, Brief Book Reviews, where I will do exactly as the title suggests: I’ll offer brief reviews of (hopefully) all the books I read this year. I hope to provide readers with at least a couple of interesting recommendations. (To see my 2019 book recommendations, see here)

First up for 2020 was Mind in Motion: How Action Shapes Thought, by Barbara Tversky. I first heard of this book on Sam Harris’ podcast where he discussed Tversky’s interesting thesis that action and motion are the basis of abstract though. The thesis was phenomenally interesting as, evolutionarily speaking, we (and other animals) evolved diverse means of communication previous to the evolution of our remarkable and complex language systems. Her thesis is doubly interesting in that one hypothesis for the ultimate function of the brain (or, centralized nervous system) that I find enchanting is that the brain ultimately evolved to facilitate locomotion — all animals must move; and, those that do not, typically don’t need a brain. Take, as a favorite example of mine, the sea squirt (and other related species) which, upon locomoting to a suitable permanent location to attach to, it promptly digests its own brain — it is no longer needed.

To continue reading, click here.

This post originally appeared on my Medium account on 22 January 2020.

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.)

To continue reading, click here.

This post originally appeared at Behavioral Scientist on 21 September 2017.

Are Life History Trade-Offs Based On Function? A New Study [IN BUGS] Suggests Caution of Basic Theoretical Assumption


When I get to my office in the morning, I go through my email and read my journal alerts of the newest academic papers published. I often come across papers that are interesting, but today I came across a paper that really blew me away. Why? Because it used a clever research design to yield big theoretical implications — my favorite kind of paper.

The paper, “A Weapons-Testes Trade-Off In Males Is Amplified in Female Traits,” by Christine Miller, Paul Joseph, Rebecca Kilner, and Zachary Emberts published in Proceedings B caught my attention. My lab recently published a paper on trade-offs in male ejaculate quality using a life history framework, so I was interested to see how the findings of this new paper contributed to this broader research area. The research did not disappoint. The results certainly found trade-offs between weapons and testes as the title implies, but with a significant twist, humbly reflected by the last part of the title “amplified in female traits.”

To continue reading, click here.

This article was originally published on my Medium account on 1 August 2019.

Why Men Have More Sex Partners Than Women


I got to my office the other morning with the goal of organizing my last data set needed for my PhD dissertation. The study is a small survey data set of 52 heterosexual couples, mostly adults in their 20s, who reported on a variety of self-report sexuality and relationship measures — pretty standard psychological research.

My topical expertise in psychology centers primarily around human sexuality. After years of studying in this area, there are two observations about human sexuality that I have more or less taken for granted at this point:

(1) Men have more sex partners than women, on average. This means that if you approach a random man on the street and ask him how many people he’s had sex with, his answer is likely to be larger than a random woman’s answer to the same question. (I don’t recommend using this approach strategy, however.)

(2) The variance, or range, of the number of sex partners within the sexes is different, with men as a group having a greater range as compared to women as a group. This means that it is likely that the most sexually successful man you know has a much larger number of sex partners than the most sexually successful woman who you know.

After my data were organized, I ran a simple analysis comparing the mean average number of lifetime sex partners between men and women to see if these basic observations held. It was unsurprising to see that my data conformed to both points: In my sample, men had a higher mean and a larger variance compared to women in their response to the question, “How many partners have you had sexual intercourse with in your lifetime?”

To continue reading, click here.

This post was originally published on my Medium account on 16 July 2019.