cycle. The closer a woman was to ovulation, the more she raised her pitch, the investigators found.
The increase in tone was only slight -- it wasn't Minnie Mouse on helium -- but the peaks were enough to be picked up by the voice decoder and presumably by the male ear, as well. The difference was the greatest on the two days preceding ovulation, when fertility within the cycle is the highest.
Curiously, this distinction only occurred when the volunteer, among the sentences she was asked to speak, introduced herself: "Hello, I'm a student at UCLA."
The scientists suggest the pitch change happens because men are lured to a more "feminine" voice in a woman -- and women respond to the instinct.
Sexual signals and reproductive fitness are strongly associated with voice, which is why women are often drawn to men with the husky voice of the supposed alpha male.
"Men prefer higher pitch relative to lower pitch in the same women, and these judgements are affected by cues of social interest in the speech," say the duo, Greg Bryant and Martie Haselton of the university's Center for Behavior, Evolution and Culture.
Previous research has found changes to body scent, an increase in flirtation, a shift towards more fashionable dress styles and a preference for more "masculine" men when women are in mid-cycle. Last year, investigators found that lap dancers earned more tips when they were fertile.
Conversely, a vocal shift towards hoarseness has been found at the time of menstruation. link