Redesigning Fraternal Birth Order Studies from Top to Bottom

Two articles in the June 2012 issue of this Journal, viewed together, raise interesting questions concerning the relationship between male sexual object orientation and erotic role orientation. The article by Schagen, Delemarre-van de Waal, Blanchard, and Cohen-Kettenis (2012) confirmed the finding in numerousearlierstudies thatgenderdysphoricadolescentmales tend tohaveasignificantlygreaternumberofolderbrothers than do males in the general population. Numerous studies have also suggested that late fraternal birth order (FBO) is similarlyamarker formalehomosexuality (e.g.,Blanchard&Lippa, 2007) and it has been shown to a high degree of certainty that the ‘‘FBO effect’’is a prenatal biological phenomenon that is unrelated to thesocialorpsychological consequencesofbeing raised witholderbrothers (Bogaert,2003,2006)In thearticlebyZheng, Hart, and Zheng (2012), it was shown that, in their study population of men who have sex with men (MSM), those who preferred to engage in receptive anal intercourse (RAI) tended to display a constellation of feminine personality traits (such as higher degrees of nurturance, agreeableness, conscientiousness, neuroticism, and sociability), while MSM who preferred insertive anal intercourse (IAI) did not. These two recent studies, one linking late FBO to male acquisition of feminine gender identity and the other linking feminine personality traits to a submissive/ receptiveerotic roleorientation,place intoquestionwhetherFBO actually isapredictorofmalehomosexualityorwhether it instead is a predictor of a submissive/receptive erotic role orientation (which in turn is associated with a certain gay phenotype). Zheng et al. (2012) first provide evidence that MSM in China, like MSM in many cultures in the Americas and in Europe, self-identify as one of three phenotypes:‘‘Tops’’(who prefer a dominant erotic role and IAI),‘‘Bottoms’’(who prefer a submissiveerotic roleandRAI), and‘‘Versatiles’’(whoenjoy RAI and IAI in substantially equal measure), and these selflabels are closely correlated to actual sexual behavior. The 220 MSM participants were tested as to their anal erotic role preferences and were also administered the 100 item International PersonalityItemPooltest forBig-Fivepersonality traits, theBem Sex Role Inventory, and various other tests for gender-related interests and identification. The data showed that Bottoms were far more apt than Tops to exhibit a constellation of ‘‘feminine’’ personality traits. As Zheng et al. noted, it is unclear whether an individual’s erotic role preference leads him to exhibit certain gendered personality traits or vice versa. However, one cannot discount the possibility that a submissive/receptive erotic role preference is but one star in a typical constellation of feminine biological traits. An individual’s sexual object orientation and erotic role orientation can be plotted against two axes: the androphilic– gynephilic axis and the dominant/insertive–submissive/receptive axis. The androphilic–gynephilic axis equates with the popular notion of sexual orientation—androphilic males being gay and gynephilic males being heterosexual. Earlier FBO studies thatargued thatFBOisabiologicalmarkerofmalehomosexuality suggested that an individual’s disposition along the androphilic–gynephilic axis might be set at birth (Bogaert, 2006). The new study by Schagen et al. (2012) suggests that FBO correlates to certain personality traits which, in turn, correlate to an individual’s position on the dominant/insertive–submissive/ receptive axis. Of course, it is possible that a person’s position along each of these two axes is a fixed and essential trait, but it is also possible that an individual’s position on one axis is fixed at birth, and that his position on the other axis is not, but the fixed characteristic influences the post-natal development of the variable characteristic. For instance, if a male has an innate submissive/receptive erotic orientation, he would be more likely than his dominant/insertive brother to develop an androphilic C. H. Wampold (&) 41 South Harrison St., Princeton, NJ 08540, USA e-mail: chwampold@mail.widener.edu