Our mouth waters because of a neurological reaction or reflex action. Russian scientist Anton Pavlov had divided reflex actions into two classes- conditional (acquired out of habitual experience) and unconditional (inborn) reflexes. Watering of mouth falls under the first category. As soon as we think of some delicious food, chemicals that transmit impulses to the brain are switched on. The brain identifies the signal and sends responses through carrier nerves to stimulate the saliva-secreting glands and our mouth begins to water.