Classical conditioning
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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." Classical conditioning originally focused on reflexive behavior or involuntary behavior. Any reflex can be conditioned to respond to a formerly neutral stimulus. A view of classical conditioning restricted to reflexes has been abandoned in recent years, and voluntary responses to conditioned stimuli have made important contributions to the field[1]
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[edit] Overview
The typical paradigm for classical conditioning involves repeatedly pairing a neutral stimulus with an unconditioned stimulus.
An unconditioned response is an automatic response brought forth by an unconditioned stimulus. These responses are automatic and require no learning and are usually apparent in all species. The relationship between the unconditioned stimulus and unconditioned response is known as the unconditioned reflex. The conditioned stimulus, is an initially neutral stimulus that elicits no response. However, when a neutral stimulus is paired with an unconditioned stimulus, learning occurs. The neutral stimulus, now known as the conditioned stimulus, brings forth the same unconditioned response, now known as the conditioned response, without being paired with the unconditioned stimulus. Conditioned stimuli are associated psychologically with conditions such as anticipation, satisfaction (both immediate and prolonged), and fear. The relationship between the conditioned stimulus and conditioned response is known as the conditioned (or conditional) reflex.
In classical conditioning, when the unconditioned stimulus is repeatedly or strongly paired with a neutral stimulus the neutral stimulus becomes a conditioned stimulus and elicits a conditioned response.
Unconditioned stimulus (U.S.) Dogs and cats have the same stimuli
Unconditioned response (U.R.)
Neutral stimulus (N.S.)
Conditioned stimulus (C.S.)
Conditioned response (C.R.)
Food (U.S.) => Salivation (U.R.) Natural response.
Food (U.S.) + Bell (N.S.) => Salivation (U.R.) After repeating the pairing a few times.
Bell (C.S.) => Salivation (C.R.) Learning occurs. Notice how the response never changes.
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.
Note too that the timing of the C.S. is critical, in that it immmediately 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.
[edit] Pavlov's experiment
The most famous example of classical conditioning involved the salivary conditioning of Pavlov's dogs. Pavlov wanted to find out how conditioned reflexes were acquired. Dogs naturally salivate to food, therefore Pavlov called the correlation between the unconditioned stimulus (food) and the unconditioned response (salivation) an unconditional reflex. 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. For example, if footsteps were frequently heard a few seconds before food was given to the dogs, eventually the footsteps would elicit salivation even without food. Before being paired with food, the footsteps were a neutral stimulus since it did not produce any response in the dogs besides curiosity. With repetition, the neutral stimulus became a conditioned stimulus. Pavlov referred to this learned relationship as a conditioned reflex.The conditioned reflex (food-related behavior elicited by a stimulus that has been reliably paired with food) is developed through classical conditioning stimulus (footsteps) and the conditioned response (salivation) as a "conditional reflex". Pavlov also repeated this experiment with other stimuli such as a metronome and vanilla and achieved the same results. It is important to note that when Pavlov presented a neutral stimulus after the unconditioned stimulus, no conditioning took place.
The origins of the two reflexes are different. The food (unconditional stimulus) [UCS] causing salivation (unconditional response) [UCR] reflex has its origins in the evolution of the species. The tone (conditional stimulus) [CS] causing salivation (conditional response) [CR] reflex has its origins in the experience of the individual animal.
[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, whos 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 on Albert was to show that behavior is learned and trained into our minds and to also 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 UCS and produces a UCR, 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 complusion 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 constucts 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] Neurological research
Much research on the neurological basis of essential learning has been conducted on the marine snail Aplysia californica, or California sea slug. While having a rather small nervous system, consisting of approximately 20 000 neurons, this snail is capable of classical conditioning, habituation as well as sensitization. This makes it suitable for experimental research on learning.[2]
[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.
