Genetic Sexual Attraction (GSA): Attraction, separation, and the boundary with incest: a critical analysis

Introduction

Within the fields of psychology and the human sciences, few phenomena are as controversial as Genetic Sexual Attraction, commonly known by the acronym GSA. The term refers to a hypothesis describing the onset of intense emotional and sexual attraction between biological relatives who, having been separated during childhood, reunite as adults (Greenberg & Littlewood, 1995). The phenomenon has been documented primarily in the context of post-adoption reunions, where individuals given up for adoption at birth meet their biological parents or siblings for the first time in adulthood.

Despite being the subject of debate among psychologists, researchers, and commentators, GSA remains one of the least explored topics in peer-reviewed scientific literature (Greenberg, 1993). This article aims to trace the origins of the concept, examine the theoretical explanations that have been proposed, compare it with the notion of incest, and critically evaluate its scientific standing, with particular reference to the most important study conducted on the subject.

Origin of the term

The term "Genetic Sexual Attraction" was introduced in the late 1980s by Barbara Gonyo, founder of the Chicago-based support group Truth Seekers in Adoption (Hipchen, 2009). Gonyo had given her son up for adoption at birth, and when she found him again — by then an adult — she experienced a powerful attraction toward him. Her son did not reciprocate the feeling, but the experience led Gonyo to gather similar accounts from within the adoptee community and among separated biological families.

In 1991, she published the book The Forbidden Love (Genetic Sexual Attraction), bringing the phenomenon to a wider audience. The term was subsequently taken up and disseminated primarily in the English-speaking world, first within adoption circles, and only later in clinical and academic contexts (Dolfi, 2021).

"People who experience GSA are having a largely normal response to a very unusual situation." 

— Greenberg (as cited in Dolfi, 2021)

Why it happens: theoretical explanations

Several hypotheses have been put forward to explain the mechanism underlying GSA, none of which has received definitive empirical confirmation (Greenberg & Littlewood, 1995).

Attraction based on genetic similarity. One of the most frequently cited explanations holds that human beings are naturally drawn to those who share similar physical, intellectual, and psychological traits (Mateo, 2022). Because genetics influences all of these characteristics to some degree, biological relatives would display a particularly high degree of similarity — the so-called phenotypic matching — which could translate into attraction when the family bond has not been established through shared childhood experience (Greenberg & Littlewood, 1995).

Mirroring. Many individuals involved in post-adoption reunions describe the shock of recognizing themselves in the other person: the same gestures, the same voice, the same interests. This phenomenon of self-recognition can generate a sense of profound and immediate familiarity that, in the absence of a shared history, may be confused with or overlaid onto romantic attraction (Dolfi, 2021).

Abandonment trauma and the missing bond. Some clinicians specializing in adoption propose that GSA is partly an expression of an unmet need for attachment (Dolfi, 2021). Early separation prevents the normal formation of parent-child or sibling bonds, leaving an emotional void that, at the moment of adult reunion, may attempt to fill itself in ways that can take on sexual connotations.

The neurobiological chemistry of falling in love. A reunion between separated biological relatives can trigger neurochemical mechanisms similar to those associated with falling in love: the release of dopamine, oxytocin, and noradrenaline (Aron et al., 2005). The emotional intensity of the encounter, combined with the novelty of the relationship and the perceived similarity, can create an altered state that some describe as "falling in love."

The Westermarck Effect: the immunity that never developed

To understand GSA, it is essential to consider its opposite: the Westermarck Effect. First described by Finnish anthropologist Edvard Westermarck in the late nineteenth century, this mechanism holds that individuals who live in close proximity during the first years of life — typically between birth and age six — develop a natural and mutual sexual aversion (Westermarck, 1891). In essence, it functions as a form of reverse sexual imprinting: the familiarity built during childhood becomes an inhibitor of sexual attraction.

The effect has been confirmed by studies conducted across a variety of cultures. One of the most frequently cited cases concerns Israeli kibbutzim, where children raised together in the same peer group showed, as adults, an extreme rarity of marriages or sexual relationships among themselves, despite the absence of any explicit social prohibition (Greenberg & Littlewood, 1995). Analogous findings emerged from studies of arranged Taiwanese marriages between children raised as adoptive siblings, which showed high rates of infidelity and dissatisfaction, attributed precisely to the sexual desensitization produced by early cohabitation (Westermarck, 1891).

GSA can therefore be interpreted as the absence of this protective mechanism: individuals who have had no contact with a biological relative during childhood have not developed the sexual aversion typical of cohabitation, and find themselves without that "immunity" when they encounter a blood relative as adults (Greenberg & Littlewood, 1995).

GSA and incest: a necessary distinction

The debate surrounding GSA becomes further complicated when its relationship to the concept of incest is addressed. The two phenomena are often conflated, but they present substantial differences from both a psychological and biographical standpoint (Dolfi, 2021).

Incest, in its traditional sense, typically occurs between individuals who have shared a childhood together, often in contexts of abuse, coercion, or highly dysfunctional power dynamics. GSA, by contrast, is by definition a phenomenon that manifests between individuals who have had no contact during childhood and who reunite as adults (Greenberg & Littlewood, 1995). As such, it lacks the context of early familiarity and — at least in theory — the asymmetric power relationship characteristic of intrafamilial abuse.

However, this distinction has been criticized by a number of experts, who point out that in clinical practice the boundaries are far less clear: dynamics of manipulation, emotional imbalances related to adoption trauma, and psychological vulnerability are frequently observed, all of which may render consent less free than it appears (Dolfi, 2021). Furthermore, the fact that GSA has been assigned its own acronym and nomenclature has been criticized for risking the conferral of a form of legitimacy — verging on medicalization — that could be exploited to justify sexually abusive behavior.

Greenberg and Littlewood (1995): the only academic study

To date, the most rigorous and widely cited study on GSA remains that conducted by British physicians Maurice Greenberg and Roland Littlewood of University College London, published in 1995 in the British Journal of Medical Psychology under the title Post-adoption incest and phenotypic matching: Experience, personal meanings and biosocial implications. It is the most important peer-reviewed contribution on the subject (Greenberg & Littlewood, 1995).

Greenberg, a consultant at the Post-Adoption Centre in London, initially approached the topic with skepticism. In the course of his research, he examined 34 cases referred to the centre involving post-reunion incestuous attractions between biological relatives separated since infancy — adult siblings and parent-child pairs — and conducted clinical interviews with the individuals involved (Greenberg & Littlewood, 1995).

The study documented recurring features across these cases: rapid idealization of the other person, a compulsive impulse toward physical contact, a marked olfactory fixation, and in several cases a progression toward sexual contact. Greenberg concluded that the individuals involved were experiencing a largely normal response to a highly unusual situation, emphasizing that the absence of a bond built during childhood was the key determining factor (Greenberg & Littlewood, 1995).

One of the cases described in the study involved an adopted woman (married to a man) who, following her reunion with her biological sister, described a gradual progression: from a need for physical closeness, to kissing, to genital contact. The proposed interpretation was that this represented a distorted attempt to resume the bond that had been severed at birth (Greenberg & Littlewood, 1995, as cited in Dolfi, 2021).

In an earlier study, Greenberg (1993) had analyzed 40 clinical cases and interviewed 10 individuals who reported having experienced this attraction — including reunions between parents and children and between siblings, both heterosexual and homosexual. Even at that stage, the author cautioned that the results could not be generalized, given the clinical and non-systematic nature of the data collection.

Criticisms: pseudoscience or real phenomenon?

Despite the study by Greenberg and Littlewood (1995) representing an indispensable point of reference, its own author acknowledged that the findings could not be generalized, owing to the very small sample size and the clinical, non-systematic nature of the data. These limitations mean that GSA remains, from a scientific standpoint, an unverified hypothesis.

The criticisms directed at GSA by the scientific community and independent commentators are of several kinds: Lack of systematic empirical research. With only one significant peer-reviewed study in three decades, GSA is virtually ignored by academic research (Greenberg, 1993). No reliable data exist on how frequently it occurs, what factors predispose individuals to it, or how it differs across various types of reunion.

The risk of legitimizing abusive behavior. Several experts in sexual abuse and child protection have expressed concern that the term GSA may be used as a justification for incestuous relationships (Dolfi, 2021). The use of an acronym and quasi-clinical language risks normalizing situations that in many cases involve power asymmetries, unresolved trauma, and psychological vulnerability.

The nature of the samples. Both the data collected by Gonyo and those gathered by Greenberg (1993) derive from individuals who self-identified as experiencing GSA or who were referred to support centres. These are therefore heavily self-selected samples that do not permit conclusions about the prevalence of the phenomenon in the general population.

The problem of consent and context. Adoption expert Catherine MacAskill has observed that GSA cases appear to be associated primarily with sudden, unplanned meetings that lack the appropriate safeguards of a carefully prepared reunion (as cited in Dolfi, 2021). This suggests that context — and not biology alone — plays a fundamental role in determining the onset of these dynamics.

Criticism of the term itself. Journalist Amanda Marcotte described GSA as pseudoscience that people have used to justify continuing unhealthy relationships (Marcotte, 2016, as cited in Dolfi, 2021). More broadly, the scarcity of empirical foundations has led many researchers to treat GSA with extreme caution, or to decline to recognize it as a legitimate diagnostic category.

Conclusions

Genetic Sexual Attraction occupies a borderland between clinical psychology, evolutionary biology, and ethical inquiry. Its existence as an experiential phenomenon — that is, as something certain individuals report experiencing — is not in dispute: the testimonies collected, though largely anecdotal, are numerous and relatively consistent (Greenberg & Littlewood, 1995; Dolfi, 2021). The problem lies in the near-total absence of rigorous scientific research examining its prevalence, mechanisms, consequences, and risk factors.

The study by Greenberg and Littlewood (1995) remains a valuable contribution precisely because it is the only one to have addressed the subject in peer-reviewed academic form, but its methodological limitations considerably narrow its scope. The scientific community has not responded with further systematic investigation, leaving a gap that risks being filled by unverified narratives or, worse, by distorted uses of the term to justify harmful behavior.

What does seem certain is that reunions between adult biological relatives separated in infancy can give rise to emotionally intense and potentially destabilizing experiences, which require adequate psychological support (Dolfi, 2021). Educating professionals and families about this possibility — without either pathologizing or normalizing it — appears to be the most responsible course of action while awaiting more solid scientific answers.

References

Aron, A., Fisher, H., Mashek, D. J., Strong, G., Li, H., & Brown, L. L. (2005). Reward, motivation, and emotion systems associated with early-stage intense romantic love. Journal of Neurophysiology, 94(1), 327–337. https://doi.org/10.1152/jn.00838.2004

Dolfi, M. (2021). Genetic sexual attraction in adoption reunion relationships. mariedolfi.com. https://mariedolfi.com/adoption-educational/genetic-sexual-attraction-in-adoption-reunion-relationships/

Greenberg, M. (1993). Post-adoption reunion: Are we entering uncharted territory? Adoption & Fostering, 17(4), 5–15. https://doi.org/10.1177/030857599301700403

Greenberg, M., & Littlewood, R. (1995). Post-adoption incest and phenotypic matching: Experience, personal meanings and biosocial implications. British Journal of Medical Psychology, 68(1), 29–44. https://doi.org/10.1111/j.2044-8341.1995.tb01811.x

Hipchen, E. (2009). Genetic sexual attraction and the creation of fatherhood: Making daddy (infamous) in The Kiss. The Journal of the Midwest Modern Language Association, 42(2), 5–22. https://www.jstor.org/stable/25674374

Mateo, J. M. (2022). Phenotype matching. In D. Pfaff & N. Volkow (Eds.), Neuroscience in the 21st century (pp. 5210–5211). Springer. https://doi.org/10.1007/978-3-319-55065-7_1668

Westermarck, E. (1891). The history of human marriage. Macmillan.