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).
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…
Nicole Barbaro, Ph.D. 
In economics, when a choice needs to be made between several mutually exclusive alternatives the opportunity cost of a choice is the value of the best alternative forgone. For men, there is virtually no opportunity cost when mating. A man can reproduce with multiple partners within a short time-frame. For women, the opportunity cost could be reproducing with a higher fitness male because she would be pregnant for nine months. For obvious reasons, men are attracted to faithful non-pregnant women, so for a woman to be seen merely associating with other men would put off a higher mate value man. It makes sense, therefore, for a woman to recruit a man of as high mate value as possible, to mate guard, and deter unwanted attention from lower mate value males. In practice the woman would secure a long-term mate in accordance with positive assortive mating. The woman would still be free to engage in extra-pair sex with men of higher mate value than her long-term partner, because the long-term partner would lose any agonistic contest to a more dominant male. This was the likely origin of the human pair-bond. The tendency of humans to form pair-bonds is universal, with an average duration of five to six years. This is enough time to produce two children. This benefits the woman further. For without such a pair-bond, she would need to seek a second man to father her second born. By which time she will be five years older, and her mate value will have decreased (fertility peaks at around 18 years old), so the father of her next child would likely be of lower mate value too. Furthermore, her husband’s mate value may well have increased, as he gains resources and seniority within the social group. We have explained why pair-bonding is in the interests of women, but what about men? A man will pair-bond with a woman if and only if the woman is of a higher mate value than the women who would be prepared to have extra-pair sex with him. He would then be guaranteed sex for the duration of the pair bond with such a woman. Indeed, marriage (in any culture) is when the husband makes an explicit contract enforceable by the whole social group to provision a woman and any resulting children in exchange for exclusive sexual access to her.
Reference:
Moxon, S. (2013). Human pair-bonding as a service to the female. New Male Studies: An International Journal, 2 (2), 24–38.
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