Ivan Pavlov

Pavlov wanted to see if external stimuli could affect this process, so he rang a bell at the same time he gave the experimental dogs food. After a while, the dogs -- which before only salivated when they saw and ate their food -- would begin to salivate when the bell rang, even if no food were present.

In 1903 Pavlov published his results calling this a "conditioned reflex," different from an innate reflex, such as yanking a hand back from a flame, in that it had to be learned. Pavlov called this learning process (in which the dog's nervous system comes to associate the bell with the food, for example) "conditioning." He also found that the conditioned reflex would be repressed if the stimulus proves "wrong" too often. If the bell rings repeatedly and no food appears, eventually the dog stops salivating at the bell.

Pavlov was much more interested in physiology than psychology. He looked upon the young science of psychiatry a little dubiously. But he did think that conditioned reflexes could explain the behavior of psychotic people. For example, he suggested, those who withdrew from the world may associate all stimulus with possible injury or threat. His ideas played a large role in the behaviorist theory of psychology, introduced by John Watson around 1913.

How Pavlovian Reflexology Works

Summing it up: an indifferent stimulus, combining with another stimulus capable to elicit an unconditioned reflex, produces an unconditioned answer. After some time the indifferent stimulus is capable, by itself, to provoke an answer that can, then, be considered a conditioned one. Those indifferent stimuli can come from external environment (auditory, luminous, olfactory, tactile and thermal stimuli) as well as from the internal environment (viscera’s, bones, joints).

The conditioned responses can be motor, secretory or neurovegetative. Voluntary or involuntary vegetative reactions can thus be conditioned. We can make those involuntary responses appear, at our will, if we use the appropriate conditioning. The conditioned responses can be excitatory (with function increase) or inhibitory (with function decrease).

There are several examples of physiological modifications in animals and in human beings through conditioning.
It is shown that conditioned reflexes originate in the cerebral cortex, which is, in Pavlov's words, "the prime distributor and organizer of all activity of the organism".

For a conditioned reflex to appear it is necessary that certain conditions are fulfilled:

1. Coexistence in time, several times repeated, of the indifferent agent and the unconditioned stimulus (in the previous example, the sound of the bell presentation of the meat);
2. The indifferent agent should some what precede the unconditioned stimulus.

(If we first give the meat and then ring the bell, the conditioned response is not established;)
3. Absence of other stimuli that could induce externally caused inhibition. If we simultaneously whip the animal or splash it with cold water, we provoke inhibition, setting loose defensive reactions;
4. In order to preserve the conditioned reflex, it is necessary to reinforce it periodically. Once the reflex is formed, the mere sound of the bell substitutes the presentation of the meat. But, if we repeatedly ring the bell without showing the meat, after a certain time the animal stops reacting with salivation and digestive secretion.