To test the effect of a woman's bust size on the rate of help offered, 1200 male and female French motorists were tested in a hitchhiking situation. A 20-yr.-old female confederate wore a bra which permitted variation in the size of cup to vary her breast size. She stood by the side of a road frequented by hitchhikers and held out her thumb to catch a ride. Increasing the bra-size of the female-hitchhiker was significantly associated with an increase in number of male drivers, but not female drivers, who stopped to offer a ride.
[h/t Kids Prefer Cheese]