Classical conditioning (also Pavlovian conditioning) is a form of associative learning. Ivan Pavlov was the first to show in what way it works. He did this in 1927, using dogs. There is one stimulus which is called neutral, and there is another, which has some meaning. If the two stimuli are often presented together, the organism learns that they belong together. As a result, it is enough to show the neutral stimulus to get what Pavlov referred this learned relationships to as a conditional reflex, or to what is today called a conditioned reflex or response.
Pavlov did the experiment with dogs. Each time before he fed the dogs, he rang a bell. The dogs then learned that when the bell rang they would be fed. So they started to salivate, when they heard the bell ring, even before they saw or smelled the food.
Together with operant conditioning, classical conditioning became the foundation of behaviorism, a school of psychology which was dominant in the mid-20th century and is still an important influence on the practice of psychological therapy and the study of animal behavior. Classical conditioning is a basic learning process.
Experiments on theoretical issues in conditioning have mostly been done on vertebrates, especially rats and pigeons. However, conditioning has also been studied in invertebrates, and very important data on the neural basis of conditioning has come from experiments on the sea slug.
According to Pavlov, conditioning does not involve the acquisition of any new behavior, but rather the tendency to respond in old ways to new stimuli.
Some therapies associated with classical conditioning are aversion therapy, systematic desensitization and flooding.
Aversion therapy is a type of behavior therapy designed to make patients cease an undesirable habit by associating the habit with a strong unpleasant unconditioned stimulus. For example, a medication might be used to associate the taste of alcohol with stomach upset.
Systematic desensitization is a treatment for phobias in which the patient is trained to relax while being exposed to progressively more anxiety-provoking stimuli (e.g. angry words). This is an example of counter-conditioning, intended to associate the feared stimuli with a response (relaxation) that is incompatible with anxiety
Flooding is a form of desensitization that attempts to eliminate phobias and anxieties by repeated exposure to highly distressing stimuli until the lack of reinforcement of the anxiety response causes its extinction. "Flooding" usually involves actual exposure to the stimuli, whereas the term "implosion" refers to imagined exposure, but the two terms are sometimes used synonymously.
Conditioned drug response
A stimulus that is present when a drug is administered or consumed may eventually evoke a conditioned physiological response that mimics the effect of the drug. This is sometimes the case with caffeine; habitual coffee drinkers may find that the smell of coffee gives them a feeling of alertness.
Signals that consistently precede food intake can become conditioned stimuli for a set of bodily responses that prepares the body for food and digestion. These reflexive responses include the secretion of digestive juices into the stomach and the secretion of certain hormones into the blood stream, and they induce a state of hunger. An example of conditioned hunger is the "appetizer effect." Any signal that consistently precedes a meal, such as a clock indicating that it is time for dinner, can cause people to feel hungrier than before the signal.
Conditioned emotional response
The influence of classical conditioning can be seen in emotional responses such as phobia, disgust, nausea, and anger. A familiar example is conditioned nausea, in which the CS is the sight or smell of a particular food that in the past has resulted in an unconditioned stomach upset. Similarly, when the CS is the sight of a dog and the US is the pain of being bitten, the result may be a conditioned fear of dogs.
As an adaptive mechanism, emotional conditioning helps shield an individual from harm or prepare it for important biological events.
In popular culture
In the 1932 novel Brave New World by Aldous Huxley, conditioning plays a key role in the maintenance of social peace, especially in maintaining the caste system upon which society is based. Another example is in Anthony Burgess' 1962 dystopian novel A Clockwork Orange in which the novel's anti-hero and protagonist, Alex, undergoes a procedure called the Ludovico technique, where he is fed a solution to cause severe nausea and then forced to watch violent acts. This renders him unable to perform any violent acts without inducing similar nausea.
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