His contribution to Physiology:
Research in
- Classical conditioning,
- Involuntary reflex actions,
- Temperament.
Pavlovian Conditioning/ Pavlov Dog Experiment
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. Pavlov
showed the existence of the unconditioned response by presenting a dog with a
bowl of food and the measuring its salivary secretions.
However, when Pavlov discovered that any object or event which the dogs learnt 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.
Pavlov knew that somehow, the dogs in his lab had learned to
associate food with his lab assistant. This must have been learned, because at
one point the dogs did not do it, and there came a point where they started, so
their behavior had changed. A change in behavior of this type must be the
result of learning.
In his experiment, Pavlov used a bell as his neutral
stimulus. Whenever he gave food to his dogs, he also rang a bell. After a
number of repeats of this procedure, he tried the bell on its own. As you might
expect, the bell on its own now caused an increase in salivation.
So the dog had learned an association between the bell and
the food and a new behavior had been learnt. Because this response was learned
(or conditioned), it is called a conditioned 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. 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.
Summary
To summarize, classical conditioning (later developed by
John Watson) involves learning to associate an unconditioned stimulus that
already brings about a particular response (i.e. a reflex) with a new
(conditioned) stimulus, so that the new stimulus brings about the same
response.
Pavlov developed some rather unfriendly technical terms to
describe this process. The unconditioned stimulus (or UCS) is the object or
event that originally produces the reflexive / natural response.
The response to this is called the unconditioned response
(or UCR). The neutral stimulus (NS) is a new stimulus that does not produce a
response.
Once the neutral stimulus has become associated with the
unconditioned stimulus, it becomes a conditioned stimulus (CS). The conditioned
response (CR) is the response to the conditioned stimulus.
Involuntary reflex actions
performed and directed experiments on digestion, eventually
publishing The Work of the Digestive Glands in 1897, after 12 years of
research. Experiments included surgically extracting portions of the digestive
system from animals, severing nerve bundles to determine the effects, and
implanting fistulas between digestive organs and an external pouch to examine
the organ's contents. This research served as a base for broad research on the
digestive system.
Temperment
Worked on reflex actions involved involuntary reactions to
stress and pain. He and his researchers observed and began the study of
transmarginal inhibition (TMI), the body's natural response of shutting down
when exposed to overwhelming stress or pain by electric shock. This research
showed how all temperament types responded to the stimuli the same way, but
different temperaments move through the responses at different times. He
commented "that the most basic inherited difference was how soon they
reached this shutdown point and that the quick-to-shut-down have a
fundamentally different type of nervous system."