What is reinforcement?

A stimulus reinforcement is feedback that enhances or intensifies a reaction to a stimulus. It creates a conditioned reflex. An association even can start out neutral, for example, ringing a bell and salivating. In a famous series of experiments by Dr. Ivan Pavlov around the turn of the 18th Century, dogs drooled when food was given them and a bell rung at the same time. After awhile the dogs would drool just at the sound of the bell. The sound of the bell started out neutral in relation to stimulating saliva but became a stimulus to salivation by creating a physiological association in the dogs with the bell sound and food, and then repeatedly reinforcing this association.