Low water levels, like at this reservoir near Gustine, Calif., bring birds and mosquitoes together and help transmit West Nile virus to humans. Rich Pedroncelli/AP hide caption

itoggle caption Rich Pedroncelli/AP

Psychologists say spanking and other forms of corporal punishment don't get children to change their behavior for the better. Science Photo Library/Corbis hide caption

itoggle caption Science Photo Library/Corbis

This human-scale lab rat cage is parked near a skate park in Denver, Colo., to make a point about the lack of science on marijuana. Richard Feldman Studio/Sukle Advertising and Design hide caption

itoggle caption Richard Feldman Studio/Sukle Advertising and Design