By LiveScience Staff Writer
updated 7/31/2006 1:44:18 PM ET 2006-07-31T17:44:18

A male dog will whine and beg in deference to a stronger dog, but will lower its voice into a guttural growl if it thinks it has a fighting chance.

Men unconsciously do a similar thing, scientists say.

A new study finds that the lower the pitch of a man's voice, the more physically dominant other men think he is. And men lower their voice pitch when addressing a man they believe to be less dominant than themselves, but raise it when speaking to someone they think is more dominant.

The findings, detailed in the July issue of the journal of Evolution and Human Behavior, could help explain why vocal pitch in men and women are so different.

Big and low
Vocal pitch, determined by the main frequencies in a voice, is about half as high in men as in women. This difference has traditionally been explained as  a product of sexual selection, in which women favored men with lower-pitched voices.

One reason women might prefer men who speak in low voices is that vocal pitch is partly related to physical size. Taller men tend to have lower voices because they have longer vocal tracts and vocal folds, the main determinants of pitch.

Vocal anatomy is also thought to signal a man's level of testosterone, a hormone linked to physical aggressiveness and prowess.

Studies have shown that women favor men with low, masculine voices during periods in their menstrual cycle when they're likely to get pregnant, and also that they prefer men with lower voices for short-term sexual flings.

How the study was done
In the new study, 111 male university students took part in what they thought was a competition against another guy for a date with an attractive female student. The participants were asked to rate social and physical dominance of themselves and a competitor.

All the male participants faced the same competitor, whose voice was recorded but who was not actually present during the experiment.

To get a baseline reading of their voices, participants were first asked to read a passage aloud. They then had to respond to the competitor after listening to him give reasons why he thought other men respected or admired him.

Men who rated themselves as more physically dominant than the competitor used a lower vocal pitch when responding to him, whereas men who rated themselves as less physically dominant tended to raise it.

The costs of faking
Like whining in dogs, a man's raising of pitch to a physically dominant man is probably an unconscious way of showing deference, said study leader David Puts of the University of Pittsburgh in Pennsylvania.

Men could fake it and lower their pitch to appear more dominant than they really are, but if someone calls their bluff in a real-world situation, the consequences could be severe.

"If you advertise dominance and can't back it up, the attacks may be worse than if you had avoided the fight to begin with," Puts told LiveScience.

An experiment with sparrows done in the 1980's provides a case in point. Male sparrows have black patches on their chests that advertise their status to other males. The more dominant and older a male sparrow is, the bigger and darker his patch is. Researchers painted dark patches on the chests of male sparrows that weren't very dominant before. The ruse worked for a while, but eventually the posers were challenged to fight.

"When they were, it was pretty bad for them because they couldn't back up the dominance that they had been claiming," Puts said.

Experiments in which wimpy female wasps were painted to mimic dominant wasps showed similar results: phonies got harassed more often and for longer periods when they got into fights.

Puts and his team think lower vocal pitch signals physical dominance more than it does social dominance, which in modern humans is typically achieved through skillful leadership and persuasion, not strength.

"Social dominance has to do with things like intelligence and social skills, which aren't necessarily related to body size or testosterone," Puts explained. "Ancestrally, if pitch was related to dominance, it was first related to physical dominance before anything else."

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