Classical Conditioning
The best-known examples of classical conditioning are the experiments conducted in the late 1800s and early 1900s by the Russian physiologist Ivan Pavlov. Initially, Pavlov was interested in the functioning of the digestive system (he received the 1904 Nobel Prize in Medicine and Physiology for that work). In experiments with dogs, he developed an experimental apparatus for measuring their saliva formation as they ate, using tubes that redirected secretions from the animals' salivary ducts. While conducting these experiments, Pavlov noticed that some dogs started salivating before they were fed.
New dogs did not salivate in this way, only those that had previously participated in similar laboratory sessions. Pavlov showed that this salivation was initiated by some stimulus associated with the earlier feeding, perhaps the ringing of a bell or just the appearing of the lab worker who fed the animals.
Thus, in classical conditioning, a stimulus not typically associated with a particular response (i.e. the ringing of the bell) is repeatedly presented around the same time as a stimulus that causes the response naturally (in the case of Pavlov's dogs, food), until the initial stimulus evokes the response on its own. This is known as a conditioned reflex.
Continuing to study this phenomenon for more than three decades, Pavlov concluded that a great deal of animal and human behavior resulted from classical conditioning. Although his view of the importance of conditioning was probably exaggerated, subsequent research has uncovered dozens of reflexes that respond to classical conditioning, including blinking of the eyes, the knee-jerk response, and stimulation of the heart, liver, kidneys, and stomach.
More recently, researchers have become interested in the effects of classical conditioning on the immune system, which creates antibodies that fight infection. Studies in mice and humans have demonstrated that when the immune-strengthening drug interferon is administered a few times combined with the odor of camphor (an aromatic compound that normally has no effect on the immune system), later exposure to camphor alone increased activity of the body's natural killer cells, which act against tumors and viruses. Similarly, animal research has suggested that classical conditioning might be useful for suppressing the body's immune response that rejects transplanted organs.
Other medical applications of classical conditioning are for combating alcohol and tobacco abuse, and to teach children to stop bedwetting.
New dogs did not salivate in this way, only those that had previously participated in similar laboratory sessions. Pavlov showed that this salivation was initiated by some stimulus associated with the earlier feeding, perhaps the ringing of a bell or just the appearing of the lab worker who fed the animals.
Thus, in classical conditioning, a stimulus not typically associated with a particular response (i.e. the ringing of the bell) is repeatedly presented around the same time as a stimulus that causes the response naturally (in the case of Pavlov's dogs, food), until the initial stimulus evokes the response on its own. This is known as a conditioned reflex.
Continuing to study this phenomenon for more than three decades, Pavlov concluded that a great deal of animal and human behavior resulted from classical conditioning. Although his view of the importance of conditioning was probably exaggerated, subsequent research has uncovered dozens of reflexes that respond to classical conditioning, including blinking of the eyes, the knee-jerk response, and stimulation of the heart, liver, kidneys, and stomach.
More recently, researchers have become interested in the effects of classical conditioning on the immune system, which creates antibodies that fight infection. Studies in mice and humans have demonstrated that when the immune-strengthening drug interferon is administered a few times combined with the odor of camphor (an aromatic compound that normally has no effect on the immune system), later exposure to camphor alone increased activity of the body's natural killer cells, which act against tumors and viruses. Similarly, animal research has suggested that classical conditioning might be useful for suppressing the body's immune response that rejects transplanted organs.
Other medical applications of classical conditioning are for combating alcohol and tobacco abuse, and to teach children to stop bedwetting.
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