Psychology professor reflects on new findings about gender, sexual orientation and love

April 2, 2007

By Mimi Ko Cruz

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; the higher a woman’s sex drive, the more she desires both men and women; men prefer good looks in a mate while women prefer honesty, humor, kindness and dependability.

These are some of the latest findings published by psychology professor Richard A. Lippa in a special section of this month’s issue of the Archives of Sexual Behavior. The special section, guest edited by Lippa, is devoted to studies based on data from a recent British Broadcasting Corporation (BBC) Internet survey of 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 was a research consultant for the 2005 BBC Science documentary “Secrets of the Sexes.” He appeared in the documentary, and as part of that project, Lippa and other researchers helped the BBC develop the Internet survey and analyze its results. The special section contains nine papers based on BBC data.

Lippa is author of two of the papers and co-author of a third. Some of his findings include:

• More gay men (13 percent) than heterosexual men (11 percent) 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) described themselves as ambidextrous, and more bisexual women (16 percent) than lesbians (12 percent) or heterosexual women (8 percent) described themselves as ambidextrous.
• When asked to rank the importance of 23 traits that they seek in a mate, men and women agreed on the top 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, whereas women ranked honesty, humor, kindness and dependability highest.

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

In addition, residents of economically developed nations valued a mate’s niceness more than those in economically undeveloped nations, according to Lippa’s analyses.

“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.

The BBC survey data also showed that, in richer nations, men value a mate’s intelligence more than women do, but the reverse is true in poorer nations.

“Perhaps the societies where both women and men bring home the bacon, 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 analyzing the BBC data on sex drive and sexual orientation, Lippa found that women with a high sex drive tended to report increased attraction to both men and women. In contrast, men with a high sex drive reported increased attraction to one sex or the other, depending on their sexual orientation.

“For most men, a higher sex drive simply intensifies their existing sexual orientation,” Lippa 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” and a renowned gender expert, 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 high sex drive energizes it,” he said.

In a study on birth order, handedness, and sexual orientation, 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 gay 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.

Current theories on why older brothers increase the odds that a man will be gay focus on biological factors, Lippa said. “Mothers may have immunological reactions to male fetuses, and the probability of such reactions increases with each additional male fetus. The mother’s immunological ‘memory’ can then affect the development of subsequent male fetuses.”

As for left-handedness, “explanations for links have focused on the effects of sex hormones and developmental instability before birth,” Lippa noted. “According to the sex hormone theory, variations in male hormone levels early in development influence both handedness and sexual orientation. One interesting fact that is consistent with the sex hormone theory is that more men than women are left-handed, perhaps because of their higher prenatal exposure to testosterone.”

Other prenatal factors such as exposure to infectious diseases and environmental chemicals may perturb early brain development, and that also can lead to unusual outcomes, such as left-handedness and homosexuality, Lippa said.

Other studies in the BBC special section address these questions: Do heterosexual and gay men and lesbians differ in their cognitive abilities? Do men’s mental faculties decline more rapidly than women’s as they age? Are the different spatial abilities of men and women molded by biology or culture?

Lippa now is working on further analyses of the BBC data, including findings on gender and sexual orientation differences in personality and gender differences in sex drive and attitudes toward casual, uncommitted sex.