Pavlov and the Conditioned Response

Nobel Prizewinner Ivan Pavlov was one of the great founding fathers of scientific psychology. As a physiologist, he worked on the formation of patterns of association by studying the process of salivation in dogs when they were fed. This is a straightforward stimulus-response situation. The dogs were kept hungry for specified periods of time, then fed by having food powder blown into their mouths. The amount of saliva they produced in response to this treatment could be measured and related to the degree of their hunger.

Here -and it complicated his original experiment- Pavlov made a key observation which was to lead him into a new area of research and finally to the formulation of influential theories which linked physiology, learning and personality. The observation was commonplace enough: the dogs often salivated before they were fed. It was Pavlov's tireless exploration of this phenomenon that earned him his place in history.

What he noticed was that the dogs anticipated food when they saw their keepers arriving with the feeding equipment. This is an associative process that we all know well. Our mouths water when we see lemons, for instance: maybe just reading the word 'lemon' or making a mental image of the fruit is enough to set off the mouth-watering response. Pavlov called the process conditioning. Today, out of respect for the physiologist's painstaking work on this basic learning process, we refer to it as classical or Pavlovian conditioning.

After his initial observation that dogs would salivate in response to the sight of food, or even of the keepers who supplied them with it, Pavlov began introducing variations into his experimental scheme. He found that if feeding was always accompanied by the sound of a tuning fork, the dogs would learn to salivate to the tuning fork alone: they would become conditioned to the noise. He introduced careful definitions to distinguish between these phenomena. Food was the unconditioned stimulus, salivation when food was given an unconditioned response; the sound of tuning fork became the conditioned stimulus and salivation consequent on that sound the conditioned response.

Pavlov showed that for conditioning to take place the period of time between the conditioned stimulus (the tuning fork sound) and the delivery of food was critical. If too long a time elapsed, conditioning did not take place. He also studied stimulus generalization. Having conditioned a dog to one note, he measured its conditioned response (its salivation) to other, different notes.

As one would expect, notes that were close to the original produced salivation; the less alike were the two notes, the less likely would the second one be to produce a conditioned response.

Albert and the White Rat

Some years after the publication of Pavlov's first experimental studies of conditioning, John B. Watson, a professor of psychology at Harvard, applied the principles of classical conditioning to a young child. Albert was a happy 11-month old who displayed no fear when shown a white rabbit, a white rat, a white fur coat, a white hairy mask-they were all neutral stimuli. But, like all children, Albert produced a 'startle' pattern, followed by fear, when a loud noise was made by striking an iron bar with a hammer. Watson showed that fear can be learned or conditioned and how, because of stimulus generalization, fear can spread from fear of one object to fear of many.

Watson took the loud noise (unconditioned stimulus) and paired it with the rat (conditioned stimulus). After a few repeats of first being shown the rat and then being alarmed by the bar being struck, Albert became conditioned and showed fear (conditioned response) to the rat. Watson showed that the conditioned fear response became generalized to other white, furry objects : the hairy mask, the rabbit, the fur coat. It should be made clear that there was no more conscious reasoning involved in Albert's conditioning than in that of Pavlov's dogs.

Given the correct conditions-especially the correct period of time between the conditioned and unconditioned stimuli conditioning takes place.

Extinction

The learned, or conditioned, response need not become fixed and permanent, but can gradually fade. Pavlov had already studied this phenomenon. He discovered that if he stopped presenting food after the sound of the tone, the sound gradually lost its effect on the dogs. A previously conditioned dog no longer associated the sound with the arrival of food and the conditioned response gradually died out. Pavlov called this effect extinction.

By repeatedly presenting young Albert with the rat and not sounding the metal bar, Watson would have been able to decondition the child. Unfortunately-both for Albert and Watson's experiment-the child was removed from the experiment before extinction could be achieved. Whatever we may think of the propriety of subjecting a baby to this sort of experience (and I personally find it distasteful), Watson's work has had lasting importance in the study of conditioning.

Continue reading: Rewards and Punishments

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