Our happy hour fact to amaze your drinking buddies with.

Scarlett JohanssonPeople instinctively lower their voice as a signal of attraction to the opposite sex

Researchers from Albright College and the University of Baltimore had male and female students phone three members of the opposite sex after only seeing their photograph. One of the pictures was rated attractive, another average and the third unattractive. The better looking the person in the picture, the more the students lowered their voice when they made the call.

Furthermore, for women, the researchers found a man with a higher-pitched voice is considered unattractive relative to those with deeper ones. This especially holds true during a woman's menstrual cycle, which, of course, is when she is most fertile.

This might finally solve the mystery of Christian Bale's absurdly low voice during the latest "Batman" -- he was obviously hopeless smitten with some temptress on the film's set.