Though Scarlett Johansson is known for her deep and torrid voice, a new study shows that women are most attractive to the opposite sex when they are ovulating — because their voices go up in pitch. Researchers Nathan Pipitone and Gordon Gallup recorded women counting from 1 to 10 at different points in their menstrual cycle, according to the New Scientist. Then they replayed the recordings to a group of men and women; across the board and regardless of gender, everyone found the women's voices most "attractive" when they were at their "peak fertility." According to the New Scientist, "The results are in line with evidence that the female voice box, or larynx, is under the influence of sex hormones." Other animals show physical evidence that they are in "heat" (experiencing estrus)— their genitals swell, they urinate more frequently — but the results of this study are giving more weight to the idea that humans experience estrus as well; the evidence is just more subtle.

Because the evidence of a woman being "in heat" has evolved to be subtle, contends the New Scientist, "Men become increasingly sensitive to the tiny changes that do occur. Other women also pick up on the changes, perhaps to keep an eye on the competition."

And speaking of female competition, a second recently released study shows that estrogen works in women in a similar manner to the way testosterone works in men in relation to competition. In alpha females who are "power motivated," reports Reuters, estrogen levels shoot up when they win, and plummet when they lose. The opposite happens in women who are not "power motivated": their estrogen levels fall when they win and rise when they lose. The relationship between estrogen and competition, according to scientists, is strongest in single women who are not on oral contraceptives.

'Sexy' Voice Gives Fertile Women Away [New Scientist]
Is Estrogen Testosterone For Women? [Reuters]