Michael's effect sizes are way off because he starts with a greatly inflated assumption of the probability of the first son being gay. According to Myers' (2005) explanation of this phenomenon in Exploring Psychology (6th ed.). "Assuming the odds of homosexuality are roughly 3 percent among first sons, they rise to about 4 percent among second sons, 5 percent for third sons and so on for each additional older brother." (p. 366) It is unclear to me if the increase is actually steady (based on the original base rate of 3%) or if it increases (3% for the second son, 4% for the third son and 4% plus one-third of 4% for the fourth son and so on). Up through 3 sons, it wouldn't make a difference but by the 10th son, it would be the difference between 11% and 32%. Of course, given the relatively small number of sons born to the great majority of women, it wouldn't make much difference.
One more point: I think that there is a paucity of research in this area not because it is not politically correct per se but because neither side in the political debate really wants to know the cause of sexual orientation. Some are happy with a vague notion of biology causing it because that becomes matched in most people's minds with the concept that it is immutable and works to their political ends. (Of course, biological and even genetic causes are not immutable.) However, they have no desire to find the actual origin of sexual orientation due to the fact that locating a biological cause is a precursor to "curing" or preventing the birth of people of an unpopular orientation. On the other side, it should be obvious that the groups who believe that homosexuality is a choice aren't going to be looking for a biological cause. The funny thing is that people who believe in choice somehow think that an environmental explanation is more in line with choice than a biological cause. Both are causal explanations that do not involve choice and can, theoretically, be altered. I am not yet ready to throw over the whole concept of interactivity between biology and environment to the dominance of either side concerning any complex human behavior. Most have elements of both biology and environment in complex interaction and I haven't seen any evidence to suggest that sexual orientation will not be found to have a similarly complex etiology. Studies that provide evidence of genetic influence also provide evidence of environmental influences (as yet unidentified). One possible interactive explanation is Bem's theory (as described by Myers, 2005), "Perhaps...genes code for prenatal hormones and brain anatomy, which predispose temperaments that lead children to prefer gender-typical or gender-atypical activities and friends. These preferences may later lead children to feel attracted to whichever sex feels different from their own. The dissimilar-seeming sex (whether or not it conforms to ones own anatomy) becomes associated with anxiety and other forms of arousal, which eventually gets transformed into romantic arousal." (pp. 367-368). This would certainly seem to fit with the anecdotes provided in the 60 minutes program. What I would like to see is some cross-cultural evidence of the development of sexual orientation in cultures where gender roles and expectations diverge from our own culture. Rick Dr. Rick Froman Psychology Department Box 3055 x7295 [EMAIL PROTECTED] Proverbs 14:15 "A simple man believes anything, but a prudent man gives thought to his steps." -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 15, 2006 10:14 PM To: Teaching in the Psychological Sciences Subject: Re: Womb memory and gay behavior On 15 Mar 2006 at 13:12, michael sylvester wrote: > According to recent research,a person's chances of being gay is a > function of the amount of older brothers one has.So a guy with one > older brother has a 20% chance,two older brothers 40%, and three older > brothers 60% chance.Apparently after the conception of the first > boy,the womb maintains a memory.And is directed towards producing a > female,but if another male is born, feminizing factors interact to > produce gay behavior. I don't understand what all the fuss is about. The fraternal birth order effect is a solid, well-established finding. As I mentioned in one of my recent posts (and as Dennis Goff also pointed out), the reseach was discussed on that _60 Minutes_ programme. However, while Dennis cited the work of Anthony Bogaert, I mentioned Ray Blanchard. Actually both should be credited as co-authors. Michael's figures don't seem too far off. Blanchard and Bogaert (1996) say that each additional older brother increases the odds of homosexuality by 33%. And "womb memory", as I understand it, is pretty much what B & B are arguing, although what is remembered, they hypothesize, is an immune reaction against male antigens. Also, while Blanchard was at the Clarke Institute of Psychiatry when first reporting on this, as I said in my previous post, it seems it's now called the CAMH (Centre for Addiction and Mental Health) after some complicated mergers of institutions. It's affiliated with the University of Toronto. I'm just disappointed we haven't heard from Paul Okami on the topic, as he's undoubtedly the most qualified on the subject on this list. Stephen Blanchard R, Bogaert AF (1996). Homosexuality in men and number of older brothers. Am J Psychiatry, 153(1):27-31. ----------------------------------------------------------------- Stephen L. Black, Ph.D. Department of Psychology Bishop's University e-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Dept web page at http://www.ubishops.ca/ccc/div/soc/psy TIPS discussion list for psychology teachers at http://faculty.frostburg.edu/psyc/southerly/tips/index.htm ----------------------------------------------------------------------- --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [email protected] To unsubscribe send a blank email to [EMAIL PROTECTED]
