On September 14, 1849, Ivan Petrovich Pavlov was born on a farm, the first of 11 children. In 1870 he went to the University of St. Petersburg, where he first studied law and natural sciences, and from 1875 he studied medicine there. In 1890 Pavlov became professor of pharmacology and later professor of physiology in St. Petersburg. He was awarded the Nobel Prize in 1904 for his contributions to the elucidation of digestive processes. Pavlov was still working daily in his laboratory in Leningrad in his 86th year. He died on February 27, 1936.
Pavlov’s famous experiment
His research on the digestive behavior of dogs became famous. Pavlov noticed during his research that whenever he showed his dogs food, they reacted with increased salivation. This is an automatic reaction that is innate to the dog. Such a behavior, which runs off unconditionally, is called an unconditional reflex.
Pavlovian dogs
Pavlov subsequently now rearranged his experiment so that a bell rang immediately before the food was given. Since there was the food now always only after a bell signal, the dog learned in the course of the time to react to the ring tone.
After some time he began to drool when only the bell sounded – even before he could see or smell the food. The dog had learned in this time that after the ring tone a reward follows inevitably. Even the perception of the sound was now enough to trigger salivation in the test dog.
The result of the experiment
The ringing with the bell was initially a neutral stimulus and had nothing to do with the food itself. Now that Pavlov had performed this experiment, the learned reflex reliably resulted in the increased secretion of saliva. The formerly neutral stimulus triggered a new reflex response from that time on. A neutral stimulus had become a conditional stimulus. This reaction described by Pavlov is called a conditioned reflex. It is a learned reflex, not a natural one.
