The credit for the discovery of the conditioned reflex goes to the Russian physiologist Ivan Pavlov (1849-1936). He won the Nobel Prize for Physiology or Medicine in 1904 for his work on the gastrointestinal system. He used a dog, a bell and a piece of meat for this experiment. The dog began to salivate when it saw the piece of meat and began to look for the sound stimulus when it heard the bell ringing. The repeated ringing of the bell followed by the dangling of the meat in front of the dog conditioned its reflexes to react accordingly–that is to instinctively start salivation immediately after the bell had been rung, because the dog was conditioned to believe that the meat would follow soon after. The following conditions must be satisfied for a conditioned reflex to appear: the indifferent agent (the ringing of the bell) must co-exist in time with the unconditioned stimulus (the dangling of the meat in front of the dog) and must be repeated several times. The indifferent agent must precede the unconditioned stimulus, there should be no other external stimuli that induce inhibition (for example, the dog would have instinctively reacted defensively if it was whipped or splashed with cold water, which was not done in Pavlov's experiment) and the conditioned reflex can be preserved by reinforcing it repeatedly.
After a series of periodic repetitions, the dog was able to relate the ringing sound of the bell with the presentation of the piece of meat. If only the bell would have been rung without presenting the meat, the dog would have gradually stopped salivating and secreting its digestive juices.
After a series of periodic repetitions, the dog was able to relate the ringing sound of the bell with the presentation of the piece of meat. If only the bell would have been rung without presenting the meat, the dog would have gradually stopped salivating and secreting its digestive juices.
