Like many great scientific advances, Pavlovian conditioning (aka classical conditioning) was discovered accidentally.
During the 1890s, Russian physiologist, Ivan Pavlov was researching salivation in dogs in response to being fed. He inserted a small test tube into the cheek of each dog to measure saliva when the dogs were fed (with a powder made from meat).
Pavlov predicted the dogs would salivate in response to the food placed in front of them, but he noticed that his dogs would begin to salivate whenever they heard the footsteps of his assistant who was bringing them the food.
When Pavlov discovered that any object or event which the dogs learned to associate with food (such as the lab assistant) would trigger the same response, he realized that he had made an important scientific discovery. Accordingly, he devoted the rest of his career to studying this type of learning.
Pavlovian Conditioning
Pavlov (1902) started from the idea that there are some things that a dog does not need to learn. For example, dogs don’t learn to salivate whenever they see food. This reflex is ‘hard-wired’ into the dog.
In behaviorist terms, food is an unconditioned stimulus and salivation is an unconditioned response. (i.e., a stimulus-response connection that required no learning).
In his experiment, Pavlov used a metronome as his neutral stimulus. By itself the metronome did not elecit a response from the dogs.
Next, Pavlov began the conditioning procedure, whereby the clicking metronome was introduced just before he gave food to his dogs. After a number of repeats (trials) of this procedure he presented the metronome on its own.
As you might expect, the sound of the clicking metronome on its own now caused an increase in salivation.
So the dog had learned an association between the metronome and the food and a new behavior had been learned. Because this response was learned (or conditioned), it is called a conditioned response (and also known as a Pavlovian response). The neutral stimulus has become a conditioned stimulus.
Pavlov found that for associations to be made, the two stimuli had to be presented close together in time (such as a bell). He called this the law of temporal contiguity. If the time between the conditioned stimulus (bell) and unconditioned stimulus (food) is too great, then learning will not occur.
Pavlov and his studies of classical conditioning have become famous since his early work between 1890-1930. Classical conditioning is "classical" in that it is the first systematic study of basic laws of learning / conditioning.
