Brothers in arms

　　袍澤之情(陳繼龍 編譯)

　　Jun 29th 2006 | TORONTO

　　From The Economist print edition

　　RAY BLANCHARD, a researcher at Toronto's Centre for Addiction and Mental Health, was reviewing some data a few years ago when he noticed something odd: gay men seemed to have more older brothers than straight men.

　　幾年前，多倫多毒癮與心理健康中心研究員雷 布朗夏爾在回顧一些數據時注意到一個奇怪的現象——同性戀男子的哥哥似乎比異性戀男子多。

　　Intrigued—and sceptical—he decided to investigate. He recruited 302 gay men and the same number of heterosexual controls and inquired about their families. How many siblings[1] did they have, _______① what sex, and how had the births been spaced? How old had their parents been when they had had them? Dr Blanchard found that only one detail seemed to predict sexual orientation: the more elder brothers a man had, the more likely he was to be gay. (1)Neither elder sisters nor younger siblings of either sex had any effect, but each additional elder brother increased his chance of being gay by about 33% from the population average of one man in 50.

　　由于對此感到好奇和懷疑，他決定做個調查。他招募了302名同性戀男子和一樣多的異性戀男子，并問及一些與家庭有關的問題：有幾個兄弟，幾個姐妹，前后出生間隔多長時間?出生時父母多大年齡?布朗夏爾博士發現，預示性取向的似乎只有一個細節：哥哥越多，成為同性戀的可能性就越大。姐姐以及弟妹的數量對某人的性取向沒有任何影響。一般而言，平均50個男人中就有1人可能成為同性戀，每多一位哥哥，此人成為同性戀的可能性就增加33%左右。