Anthony Bogaert has a new study out today about the older brother theory. Well, technically tomorrow, since it is not out on the Proceedings of the National Academy of Science website yet. This study seems to leave the “feared older brother” theory looking pretty shabby. However, the hype over the study is sure to overlook Blanchard and Bogaert’s estimates that only about 15% of gay men owe their attractions to this effect.
I have been reviewing prior work in this area today. About half of the studies looking for a birth order effect have found it. The studies have either found no effect or an elevated ratio of brothers to sisters of gay men. One study examined the feminity hypothesis. Anthony Bogaert looked for a birth order effect in a general sample of homosexual men and then in very feminine men. He found it in very feminine gay men but not in a general sample, even among more feminine (but non – gender identity disordered) gay men. I would like to see a general study of cross gender behavior and sex ratio but this was not examined. In any case, cross gender behavior in childhood does explain some of the orientation in extremely feminine cases but not in all cases.
This study like most biological studies is a challenge for the media to report. Here a potentially very misleading statement from the LA Times writer: “In an analysis of 905 men and their siblings, Canadian psychologist Anthony Bogaert found no evidence that social interactions among family members play any role in determining whether a man is gay or straight.” Of course it is correct; the authors found no evidence, but the statement leaves the impression that the authors looked for all possible “social interactions between family members” and didn’t find anything. It appears they only looked a birth order.