Spit personality

In the name of spit science, Douglas Granger and his colleagues have collected saliva samples from a restless polar bear, a college marching band and Navy medics dodging bullets in simulated combat. The mouthwatering liquid is a gold mine of information, says Granger, an "oral fluid" expert. A fraction of a drop of spit can be used to measure stress, decipher relationship dynamics, predict heart trouble and even help football players train more effectively.