Issues pertaining to human sexuality and gender roles have long been of interest to psychologists, and have been of general interest to nearly every generation of human beings. The nature of romantic and erotic attraction dominates the world of literature, music, and other art forms, while the efforts to understand what drives or determines the way that individuals manifest romantic and erotic attraction and inhabit gender roles has been the subject of extensive research in recent decades. The earliest research into these areas largely presumed that issues such as gender identity and sexual orientation were generally innate, and that environmental factors during childhood, adolescence, and other developmental stages were responsible for the manifestation of gender identity issues, homosexuality, bisexuality, and other deviations from what was considered to be normal expressions of gender identity and sexual orientation. In recent years a number of researchers have uncovered evidence of biological and physiological factors that influence gender identity and sexual orientation, serving to underpin the so-called “nature vs. nurture” debate with regards to these issues. In the article “Biased-Interaction Theory of Psychosexual Development: ‘How Does One Know if One is Male or Female?’ ” (Diamond, 2007) a strong case is made for the theory that the development of gender identity and sexual orientation requires the interplay of both inherent biological factors and environmental factors.
The theoretical construct proposed by Diamond focuses largely on issues of gender identity, but also takes into consideration the issue of sexual orientation, and notes that there are correlations in terms of expressing sexual preferences and the development of gender identity. Diamond proposes that “early biological factors that organize predispositions in temperament and attitudes. With activation of these factors a person interacts in society and comes to identify as male or female.” Similar studies have been conducted that focus primarily on the issue of sexual attraction and sexual orientation, and have reached similar conclusions: that biological predispositions towards certain behaviors or interests are “activated” by environmental actors to determine sexual orientation. In the context of these theories, then, it is possible to have biological predispositions towards expressions of gender identity or sexual orientation that are not activated by the noted environmental factors, or that are activated such that individuals develop expressions of these traits that fall in different areas on the spectrum between “male” and “female” or between “heterosexual” and “homosexual.” As Diamond notes, research into these areas must rightly consider that there are more than simple binary expressions of gender identity and sexuality, and that many (if not most) people fall somewhere in between two rigidly-defined polar opposites.
The core of Diamond’s theory is that human beings routinely compare themselves with others deciding who they are like (same) and with whom are they different,” and that there are a number of biological and environmental determinants that interact during the development of gender identity and sexuality to establish how these traits will manifest themselves in individuals. During what might be considered as “normal” development, individuals measure themselves against members of the opposite gender and the same gender, and the shared similarities and perceived differences help to inform behavioral models and support innate biological processes that lead to the development of conforming or “normal” gender identities and sexual orientations. When certain biological tendencies are present, however, the perceptions of differences and similarities between others of the same and the opposite gender are skewed; as such, the sense of “the other” is equally (or at least similarly) seen in those of the same gender.
Diamond lays the groundwork for his argument by discussing historical antecedents to his own theory. For decades the predominant theories of the development of gender identity and sexuality held –according to Diamond- that the development of such traits was largely determined by environmental causes. Quoting Money, Hampson, and Hampson (1955), Diamond writes, “in place of a theory of instinctive masculinity or femininity which is innate, the evidence of hermaphroditism lends support to a conception that psychologically, sexuality is undifferentiated at birth and that it becomes differentiated as masculine or feminine in the course of the various experiences of growing up.” It must be noted, of course (as Diamond rightly points out) that such conceptions of the development of human sexuality were largely developed in the absence of the understanding of endocrinology and hormonal development and function. As our understanding of such functions has developed, concomitant research has uncovered irrevocable and significant links between hormonal functions and sexuality; contemporary research has, in fact, begun to focus in great measure on the links between biology and sexuality.
The underlying premise of Diamond’s theory holds that both nature and nurture are responsible for the development and expression of human sexuality, and he offers a range of evidence to support his position. Quoting his own earlier work, Diamond writes “behavior is a composite of prenatal and postnatal influences with the postnatal factors superimposed on a
definite inherent sexuality” (1965). In order to affirm the position he assumes, Diamond discusses the underlying chromosomal functions that determine physical expressions of gender, and examines a number of psychological studies that have examined gender and sexuality from an environmental standpoint.
Diamond first stipulates that different chromosomes typically “produce males that develop into boys” and “females that develop into girls,” and describes these differences as “organizing factors.” These organizing factors are then typically reinforced by social and cultural forces during development in a manner that tends to produce a majority of females who identify as female and as heterosexuals and males who identify as males and are heterosexual. The environmental factors that then mold the expression of these organizing factors during development are labeled “activating processes” (a term which serves to underscore the fact that, as “processes,” these factors are not static, but are parts of the larger ongoing process of development). While the description of Diamond’s theory as just described is intended to be clear and accurate, it must also be noted that he elucidates a wide range of additional factors and issues related to the development and expression of sexuality, thereby reinforcing the notion that such expressions can and do manifest in a variety of ways from one individual to the next.
To support his theory from a psychological perspective, Diamond refers to a wide range of studies; some are among those he has conducted, while others have been carried out by other researchers. In these studies, a variety of different “types” of individuals are examined from those who express normative gender and sexuality to those who express non-normative gender identities, those who indentify as bisexual or homosexual, and other manifestations of sexual and gender identity. Diamond’s findings show that most of those who express non-normative sexuality report having felt “different” from other members of the same gender from a very young age. By decoupling such findings from anecdotal or statistical evidence supporting specific environmental factors (such as a “domineering mother” or a “weak father”), Diamond posits that non-normative expressions of gender or sexuality at a young age are driven by hormonal and other biological processes and functions. Where normative expression would underpin an individual’s tendency to see members of the same gender as being similar, and members of the opposite gender as being different, these normative tendencies are subverted or altered. Given the right set of activation processes during adolescence and puberty, the combination of biological and environmental factors that typically result in normative expressions of gender and sexuality can result in atypical expressions and manifestations of gender roles and sexual identity.
Diamond’s full report is quite extensive and detailed, and explores both the physiology and psychology of sexuality, gender, and sexual orientation to in much greater depth than can be fully described in this discussion. In sum, however, there is no question that Diamond makes a strong and compelling case for his theory and his perspective on human sexual development. When looking at either side of the nature vs. nurture debate, neither serves to adequately account for all of the factors that combine to support the expression of individual sexual identity. Just as there are a great number of different ways that individuals can express gender identity and sexual orientation, Diamond posits that there are a variety of factors, both physiological and psychological, which combine in different ways to determine such expressions. By attempting to account for as many of these factors as possible, Diamond effectively demonstrates that simply looking to “nature” or “nurture” to the exclusion of all else no longer appears to offer an adequate explanation for the multiplicity of ways in which human beings express their gender roles and sexual identities.
Diamond, M. (2007). Biased-Interaction Theory of Psychosexual Development: “How Does One Know if One is Male or Female?”. Sex Roles, 55(9-10), 589-600.