On Tue, 15 Jan 2002, Michael Sylvester wrote: > if gay behavior is genetically based,shouldn't we expect that if one > member of an identical twin is gay that the other one would also be gay?
Yes indeed. Checking the brand-new 4th edition of Plomin et al's authoritative text _Behavioral Genetics_, I see that he cites Bailey & Pillard's 1991 study as the most reasonable for homosexuality (an early study found 100% concordance). Bailey reported 52% concordance for identicals and 22% for fraternals. Applying some standard formulae, I come up with heritability of 0.60, non-shared environment of 0.48 (plus error, I guess), and no contribution of the shared family environment. So much for theories that it's upbringing (e.g. weak father, domineering mother) that's responsible. -Stephen ------------------------------------------------------------------------ Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470 Department of Psychology fax: (819) 822-9661 Bishop's University e-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy Check out TIPS listserv for teachers of psychology at: http://www.frostburg.edu/dept/psyc/southerly/tips/ ------------------------------------------------------------------------ --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
