by dr. saul mcleod, updated 2021
Like many great scientific breakthroughs, Pavlovian conditioning (also known as classical conditioning) was discovered accidentally. ivan petrovich pavlov (1849-1936) was a physiologist, not a psychologist.
during the 1890s, russian physiologist ivan pavlov was investigating the salivation of dogs in response to feeding. he inserted a small test tube into each dog’s cheek to measure the saliva when the dogs were fed (with a powder made from meat).
pavlov predicted that dogs would salivate in response to food being put in front of them, but he noticed that his dogs would start to salivate whenever they heard the footsteps of their assistant bringing them food.
When pavlov discovered that any object or event that dogs learned to associate with food (such as the lab assistant) would trigger the same response, he realized he had made an important scientific discovery. consequently, he devoted the rest of his career to studying this type of learning.
pavlov (1902) started from the idea that there are some things that a dog does not need to learn. for example, dogs do not learn to salivate every time they see food. this reflex is ‘hardwired’ in the dog.
In behavioral terms, food is an unconditioned stimulus and salivation is an unconditioned response. (ie, a stimulus-response connection that did not require learning).
in his experiment, pavlov used a metronome as a neutral stimulus. by itself, the metronome did not elicit a response from the dogs.
Next, Pavlov began the conditioning procedure, whereby the clicking metronome was introduced just before feeding his dogs food. after several repetitions (rehearsals) of this procedure, he presented the metronome alone.
as expected, the sound of the metronome alone now caused increased salivation.
then the dog had learned an association between the metronome and food and had learned a new behavior. 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 discovered that for associations to be made, the two stimuli had to be presented together in time (like a bell). he called this the law of temporal contiguity. if the time between the conditioned stimulus (bell) and the unconditioned stimulus (food) is too long, then learning will not occur.
pavlov and his studies on classical conditioning have become famous since his early work between 1890 and 1930. classical conditioning is “classical” in the sense that it is the first systematic study of the basic laws of learning/ conditioning.
To summarize, classical conditioning (later developed by Watson, 1913) involves learning to associate an unconditioned stimulus that already elicits a particular response (i.e., a reflex) with a new (conditioned) stimulus, so that the new stimulus generates the same response.
pavlov developed some unfriendly technical terms to describe this process. the unconditioned stimulus (or ucs) is the object or event that originally produced the reflexive/natural response.
the response to this is called an unconditioned response (or ucr). the neutral stimulus (ns) is a new stimulus that does not produce a response.
once the neutral stimulus has been associated with the unconditioned stimulus, it becomes a conditioned stimulus (cs). the conditioned response (cr) is the response to the conditioned stimulus.
classical conditioning is learning through association and was first demonstrated by ivan pavlov. Pavlov showed that dogs could be conditioned to salivate at the sound of a bell if that sound was repeatedly presented at the same time that they were given food.
first the dogs were presented with food, they salivated. food was the unconditioned stimuli and salivation was an unconditioned (innate) response. then pavlov rang the bell (neutral stimulus ) before giving the food.
after a few pairings, the dogs salivated when they heard the bell, even when no food was given. the bell had become the conditioned stimulus and salivation had become the conditioned response.
The dogs had learned to associate the rattle with food and the sound of the rattle, and salivation was elicited by the sound of the rattle.
pavlov showed that classical conditioning leads to learning by association. watson and rayner demonstrated that phobias can be learned through classical conditioning in the “little albert” experiment.
references to apa style
pavlov, i. p. (1897/1902). the work of the digestive glands. london: griffin.
pavlov, i. p. (1928). lectures on conditioned reflexes. (Translated by W.H. Gantt) London: Allen and Unwin.
pavlov, i. p. (1927). Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. translated and edited by anrep, gv (oxford university press, london, 1927).
pavlov, i. p. (1955). selected works. moscow: publishing house of foreign languages.
watson, j. b. (1913). psychology as the behaviorist sees it. Psychological Review, 20, 158-177.