Fraternal Birth Order, Handedness, and Sexual Orientation in a Chinese Population

Abstract

We examined the relationship between handedness, fraternal birth order, and sexual orientation in a Chinese population, and analyzed the influence of the components assessing sexual orientation and criteria classifying individuals as homosexual on this relationship. A large sample of heterosexual, bisexual, and homosexual men and women participated in a web-based survey. Our results showed that homosexual women are more likely to be non-right-handed than heterosexual women, regardless of how sexual orientation was defined, whereas bisexual women are more likely to be non-right-handed than heterosexual women when sexual orientation was assessed via sexual attraction and sexual identity. Bisexual men are more likely to be non-right-handed than heterosexual men when sexual orientation was assessed via sexual attraction. We found neither a fraternal birth-order effect nor an interaction between sibling sex ratio, handedness, and sexual orientation. The small number of siblings may be the reason why we could not replicate the fraternal birth-order effect in this Chinese population, which highlights the importance of cultural differences in the understanding of handedness, fraternal birth order, and sexual orientation.

Notes

¹ This study used a 7-point Kinsey-like scale ranging from 1 (Exclusively homosexual) to 7 (Exclusively heterosexual) and classified individuals with a score between 1 and 4 as homosexual. When we transform this scale to a 7-point scale ranging from 0 (Exclusively heterosexual) to 6 (Exclusively homosexual), individuals with a score equal to or higher than 3 are classified as homosexual.