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Psychology Professor Studies Secrets of the Sexes
Data From More Than 200,000 Worldwide Analyzed for Gender Differences

March 29, 2007 :: No. 155

Gay men and lesbians are more likely to be left-handed than heterosexuals; the more older brothers a man has, the more likely he is to be gay; when choosing a mate, men prefer good-looking women, while women prefer honesty, humor, kindness and dependability; and the higher a woman’s sex drive, the more she desires both men and women.

These are some of Cal State Fullerton psychology professor Richard A. Lippa’s findings from his latest research, to be published in a special section of the April issue of the psychology journal “Archives of Sexual Behavior.” The special section, guest edited by Lippa, is devoted to studies based a British Broadcasting Corp. (BBC) Internet survey that collected data from more than 200,000 people worldwide.

The survey focused on gender differences in various traits and behaviors, including cognitive abilities, sexual attitudes, personality and mate preferences, Lippa said.

Lippa was a research consultant for the 2005 BBC documentary “Secrets of the Sexes.” He also appeared in the documentary. As part of that project, Lippa and other researchers helped the BBC develop the Internet survey; their analysis of the data constitutes the special section of the journal. It contains nine papers based on the BBC data. Lippa is author of two of the papers and co-author of a third.

His studies produced these findings:

  • More gay men (13 percent) than heterosexual men (11percent) and more lesbians (11 percent) than heterosexual women (10 percent) reported being left-handed.
  • More bisexual men (12 percent) than gay or heterosexual men (8 percent) describe themselves as ambidextrous, and more bisexual women (16 percent) than lesbians (12 percent) and heterosexual women (8 percent) reported “mixed hand preferences.”
  • When asked to rank the importance of 23 traits to seek in a mate, men and women agreed on nine — intelligence, humor, honesty, kindness, good looks, facial attractiveness, values, communication skills and dependability. But men ranked good looks and facial attractiveness higher than the other traits, while women ranked honesty, humor, kindness and dependability higher.

“Differences in the importance men and women assigned to a mate’s looks were extremely consistent across 53 nations, suggesting an evolved, biological component to this difference,” Lippa said.

However, residents of economically developed nations assigned more importance of a mate’s niceness than those in economically undeveloped nations, according to the survey.

“Seeking a nice mate with pleasant personal qualities may be a luxury available to people in affluent countries more than to people in poorer nations,” Lippa said.

In richer nations, the survey said, men value a mate’s intelligence more than women do, and the reverse is true in poorer nations. “Perhaps, in the societies where women bring home the bacon as well as men, men come to value an intelligent mate, but in societies where women tend to stay sequestered at home, men don’t place as high a premium on a mate’s intelligence,” Lippa said.

In his survey about sex-drive differences, he found that nearly twice as many women with high sex drives than men with high sex drives throughout the world desire men and women. In contrast, the higher a man’s sex drive, the more he desires one sex or the other, depending on his sexual orientation, Lippa reported.

“For most men, a higher sex drive simply intensifies their existing sexual orientation,” he said. “The unexpected result is that women seem to be more intrinsically bisexual in their sexual attractions. Men tend to be either-or [heterosexual or gay], but women have more shades of gray.”

Lippa, author of the 2005 book “Gender, Nature and Nurture,” said the findings suggest that sexual orientation is fundamentally different in men and women.

“It seems that in most women, there is a latent bisexuality, and that high sex drive energizes it,” he said.

In his study about birth order, Lippa and Canadian psychologist Ray Blanchard found that when compared to heterosexual men, gay men are more likely to have more older brothers — a phenomenon termed “the fraternal birth order effect.”

Other findings revealed:

  • Among right-handed men, each additional older brother increased a man’s odds of being homosexual or bisexual by 15 percent. Older sisters had no effect.
  • Left-handed men did not show the fraternal birth order effect. However, they showed some evidence of a “family size effect”: additional brothers and sisters, or larger family sizes, increased their odds of being gay or bisexual.
  • Gay and bisexual men tend to have more siblings than heterosexual men. In contrast, bisexual women tend to have fewer siblings than heterosexual and lesbian women.

“Explanations for links between handedness and sexual orientation have focused on the effects of sex hormones and developmental instability before birth,” Blanchard and Lippa noted. “According to the sex hormone theory, variations in male hormone levels early in development influence both handedness and sexual orientation. According to developmental instability theory, prenatal factors, such as exposure to infectious diseases and environmental chemicals, may perturb early brain development, and this can sometimes lead to unusual outcomes, such as left-handedness and homosexuality."

Media Contacts:

Richard A. Lippa, Psychology, 657-278-3654 or
Mimi Ko Cruz, Public Affairs,  657-278-7586 or

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Richard Lippa
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