Classical conditioning
From Wikipedia, the free encyclopedia
 |
This article may require cleanup to meet Wikipedia's quality standards. Please discuss this issue on the talk page or replace this tag with a more specific message. This article has been tagged since June 2006. |
Classical conditioning (also Pavlovian conditioning, respondent conditioning or alpha-conditioning) is a type of associative learning. Ivan Pavlov described the learning of conditioned behavior as being formed by pairing stimuli to condition an animal into giving a certain response. The simplest form of classical conditioning is reminiscent of what Aristotle would have called the law of contiguity, which states that: "When two things commonly occur together, the appearance of one will bring the other to mind."
Contents |
[edit] Overview
The typical paradigm for classical conditioning involves repeatedly pairing a neutral stimulus with an unconditioned stimulus. After such repititive pairings, the neutral stimulus becomes a conditioned stimulus and elicits a conditioned response which is very much similar to the unconditioned response brought forth by an unconditioned stimulus.
[edit] Pavlov's experiment
The most famous example of classical conditioning involved the salivary conditioning of Pavlov's dogs. Dogs naturally salivate to food. He predicted that if a particular stimulus in the dog’s surroundings was present when the dog was presented with food then this stimulus would become associated with food and cause the dog to salivate. In his initial experiment, Pavlov used bells to call the dogs to their food, after a few repetitions, Pavlov no longer needed the food. The food had been associated with the ringing of the bell, therefore a neutral stimulus became a conditioned stimulus and had created the unconditioned response of salivation. Pavlov referred to this learned relationship as a conditioned reflex.
Note too that the timing of the C.S. is critical, in that it immediately preceeds the U.C.S. and is a reliable method of prediction. When the order is reversed, for example, this is called backward conditioning and is usually ineffective.
There are two competing theories of how classical conditioning works. The first, stimulus-response theory suggests that an association with the UCS is made with the C.S. within the brain, but without involving conscious thought. The second theory stimulus-stimulus theory involves a cognitive component, in which the C.S. is associated with the concept of the UCS, a subtle but important distinction.
[edit] John B. Watson's Little Albert
John B. Watson proposed that emotions (such as fear) can be conditioned in a human being. He believed that such a task could be completed by supplying a stimulus, which causes a response naturally (unconditioned stimulus) at the same time as another object, which does not evoke a response at all (neutral stimulus).
In his experiment, Watson created a fear response in an eleven month old child, Albert, whose mother was a wet nurse at the Harriet Lane Home for Invalid children. Albert's life was normal. He was a very healthy child and one of the best developed infants that had been brought to the hospital. Albert was an easy child, who rarely even cried.
Before starting the experiment, Watson had to find out if the child was afraid of objects. During this part of the experiment, Watson showed the boy several objects like a rat, rabbit, monkey, dog, cotton wool and masks with and without hair. Watson verified that Albert did not have any fear towards these objects and therefore proceeded with the rest of the experiment. The objects that Albert are shown are the neutral stimuli of this experiment. After establishing some neutral stimuli, Watson found an unconditioned stimulus, which in this case was a loud noise made by banging a hammer on a steel bar. When the loud noise was made, Albert cried and was frightened.
When Albert was 11 months old the actual experiment started because there was hesitation about the ethics of continuing with such an experiment. To condition fear in Albert, Watson and his crew presented the rat and the noise at the same time. Albert would reach for the rat and at that moment the noise would occur. This procedure was performed a total of seven times over the course of one week. After these seven rat and noise pairs, the rat was given to Albert alone. At this point, Albert was stricken with fear and attempted to get very far away from the rat.
Continuing on with the experiment, the researchers wanted to determine if Albert’s fear would transfer to similar objects (this is called generalization). The researchers showed Albert a rabbit, a fur coat, a dog, and Watson’s gray hair and all these items produced fear in little Albert even though he was not conditioned to fear these items. Five days later Albert’s fear reaction was tested. All the items still evoked fear in the infant. Watson moved Albert to a different room to find out if the fear would still be present in different situations. If the fear only existed in the experimenting room then the results of the study would not be useful. Indeed, the fear did carry over into the other room but not in as much intensity.
The testing of Albert’s fear responses was temporarily stopped for thirty-one days because Albert was being adopted and Watson wanted to see if Albert’s fear would continue over time. After the 31 days, Albert was tested once again and the researchers found that Albert indeed still had the fear of the objects from the beginning of the experiment.
At the end of the experiment, Watson wanted to recondition Albert to not fear these objects but did not have the opportunity because Albert was adopted and removed from the hospital.
The goals of Watson’s experiments was to prove behavior is learned and to show that the Freudian thinking was wrong. Freudian thinkers believed that behavior comes from the unconscious. Watson’s experiment of little Albert explained behavior in simple terms.
Watson’s study goes against the ethical conduct of today’s society. Moreover, Albert was allowed to leave the experiment without being reconditioned. Watson states in his article of the study that such emotions can last over the life of the individual. Recent research has found that if the individual is not properly conditioned then the results may not last as long as a lifetime. The results of conditioned emotions can be shaped and changed due to experiences. This disappearance of the conditioned response is called extinction.
On another note, Watson’s study has been considered in studies and treatments of phobias. Phobias are extreme forms of fear that cause problems in everyday functioning.
[edit] Behavioral therapies based on classical conditioning
In human psychology, implications for therapies and treatments using classical conditioning differ from operant conditioning. Therapies associated with classical conditioning are aversion therapy, flooding, systematic desensitization, and implosion therapy. Implosion therapy and "flooding" involve forcing the individual to face an object/situation giving rise to anxiety; both of these techniques have been criticized for being unethical since they have the potential to cause trauma.
Classical conditioning is short-term, usually requiring less time with therapists and less effort from patients, unlike humanistic therapies. The therapies mentioned in the last paragraph are intended to cause either aversive feelings toward something, or to reduce the aversion altogether. Classical conditioning is based on a repetitive behaviour system.
When a behavior that has been strongly reinforced in the past no longer gains a reinforcement, an extinction burst may occur. The animal repeats the behavior over and over again, in a burst of activity, then stops permanently.
[edit] Aversion therapy
This is a form of psychological therapy that is designed to eliminate, for example, sexual behaviour by associating an aversive stimulus such as nausea with sex. Because the aversive stimulus performs as a US and produces a UR, the association between the stimulus and behaviour leads to the same consequences each time. If the treatment has worked, the patient will not have a compulsion to engage in such behaviours again. This sort of treatment has been used to treat alcoholism as well as drug addiction.
[edit] Systematic desensitization
Patients might learn that the object of their phobias or fears are not so fearful if they can safely relive the feared stimulus. However, anxiety often obstructs such recovery. This obstruction is overcome by reintroducing the fear-producing object gradually by a process known as reciprical inhibitions. A person constructs a hierarchy of events leading to the feared situation. This hierarchy is approached step by step and anxiety is relieved at every level. The fear is eventually removed if the therapy is performed correctly.
[edit] Neural structures involved in classical conditioning
The cerebellum appears to be involved in classical conditioning. Researchers demonstrated that lesions to pathways from the cerebellum stop the conditioned response, but do not stop the unconditioned response.[1]
[edit] Further reading
- Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex (translated by G. V. Anrep). London: Oxford University Press.
[edit] See also
- Backward conditioning
- Behaviorism
- Eyeblink conditioning
- Learned helplessness
- Nocebo
- Operant conditioning
- Placebo (origins of technical term)
- Rescorla-Wagner model of conditioning
- S-R theory
- S-S theory
- Second-order conditioning
- Taste aversion
- Edwin B. Twitmyer
