mediocre student, he first attended the church school in Ryazan and then the theological seminary. He had planned to pursue a career in theology but was so influenced by Russian translations of Western scientific writ-ings, particularly those with Darwinian overtones, that he abandoned his religious training (Windholz, 1997). In 1870, Pavlov studied physics, mathematics, and natural science, which led him to become interested in physiology and medicine. Five years later, in 1875, he earned a degree in natural sciences. He continued his education in physiology at the Acad-emy of Medical Surgery and earned a gold medal four years later. In 1883, he identified basic principles of the functions of the heart and the nervous system.
Pavlov’s experiments showed that there was a basic pattern in the reflex regulation of the circulatory systems. This worked earned him a Nobel Prize in 1904.
This led the way for new advances in medicine. One of Pavlov’s experi-ments revealed that the nervous system plays a significant role in regulat-ing the digestive process. This research into the digestive process led him to comprehend and explain the science of conditioned reflexes. Thus, Pavlov’s research techniques developed into a method that scientists used to objectively record physical manifestations of psychic activity (Pavlov, 1927).
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Ivan Petrovich Pavlov
CLASSICAL CONDITIONING
The professional literature has fully documented Pavlov’s experiments in de-veloping conditioned reflexes in his dog (Hergenhahn & Olson, 1997; Klein, 1996). He devised a series of experiments in what became known as classical conditioning. Essentially Pavlov created a form of sign language by pairing a neutral stimulus with an unconditioned stimulus until the former became a sign that substituted for the latter in eliciting a response. The first response classically conditioned by Pavlov was the salivary reflex.
According to Ormrod (1999), Pavlov’s experiment in conditioning his dog resulted in a stimulus-response sequence. The sequence is modified based upon a three-step method.
1. First, a researcher delivers a neutral stimulus (NS), to which the organ-ism does not respond. Pavlov originally rang a bell, a neutral stimulus that did not elicit salivation.
2. A researcher then delivers a second stimulus, called an unconditioned stimulus (UCS), the organism’s response to which is called an uncondi-tioned response (UCR) because the organism responds to the stimulus without the need for conditioning. In Pavlov’s experiment, meat pro-vided an unconditioned stimulus to which the dog responded with the unconditioned response of salivation.
3. When the researcher pairs steps 1 and 2, the neutral stimulus now elic-its a response. The NS has become a conditioned stimulus (CS) to which the dog has learned a conditioned response (CR). The UCS and UCR are an unlearned stimulus-response unit called a reflex.
THE CLASSICAL CONDITIONING MODEL
Classical conditioning has been conducted on a number of organisms and hu-mans (Lipsitt & Kaye, 1964; Macfarlane, 1978; Reese & Lipsitt, 1970;
Thompson & McConnell, 1955). The classical conditioning model becomes active when two stimuli are presented to an organism at approximately the same time. When the UCS brings about a response automatically within an organism, in essence, the organism has no control over the response (Her-genhahn & Olson, 1997; Hollis, 1997).
In classical conditioning the conditioned stimulus precedes the uncondi-tioned stimulus, and, as with most sequential events, the time relations be-tween these two stimuli are crucial. Conditioning is faster when the CS is fol-lowed almost immediately by the UCS. The best interval to use in a reaction time experiment in humans is about a half second, which is usually the opti-mal interval between the warning stimulus and the signal to respond. A half
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second is also roughly the time to alert the cerebral cortex to its optimal level of arousal for acting on incoming stimuli. All these time relations suggest that the conditioned stimulus acts as a signal that prepares the organism for the on-coming unconditioned stimulus (Hergenhahn & Olson, 1997).
A longer preparation time requires a longer interval between the CS and UCS, such as occurs in either delayed or trade conditioning, both of which re-quire a nervous system that can maintain excitation after the stimulus has ceased to act. Animals with such nervous systems have more time to prepare for oncoming events, which means that they can employ strategies and tactics instead of only reflexes.
Classical conditioning is also referred to as learning through stimulus sub-stitution, since the neutral conditioned stimulus, after being paired with the un-conditioned stimulus, often enough can then be substituted for it, becoming a conditioned stimulus. The CS will evoke a similar, but weaker, response. Clas-sical conditioning is also known as signal learning, because the CS serves as a signal for the occurrence of the CR, which was previously an UCR.
Most responses that can reliably be elicited by stimuli can be classically conditioned. For example, the knee-jerk reflex, the eye-blink reflex, and the pupillary reflex can all be conditioned to various stimuli (Lefrancois, 1999).
The more time that elapses between the signal and the subsequent event, the more effectively the subject can prepare for the event, which is of special importance when the event is noxious or potentially harmful. At intervals slower than a half second or greater than two seconds, the conditioning process slows. There are three possible time intervals, known as simultane-ous, delayed, and trace conditioning (Klein, 1996). Backward conditioning, extinction, higher-order conditioning, and discrimination are also factors in the study of classical conditioning.
Simultaneous Conditioning
The CS and UCS start and end at the same time, but very little conditioning results. An example, according to Klein (1996), would be an individual walk-ing into a fast-food restaurant. This individual would experience the restau-rant (CS) and the fragrance of the food (UCS) at the same time. The simulta-neous conditioning in this case would lead to weak hunger conditioned by the mere presence of a fast-food restaurant.
Delayed Conditioning
Delayed conditioning occurs when the conditioned stimulus (CS) onset pre-cedes the onset of an UCS. When the CS first appears, “CS occurs immedi-ately after the onset of the CS,” but eventually it is delayed until the onset of the UCS. For example, a person who experiences a darkened sky (CS) that
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precedes a severe storm (UCS) may develop a delayed conditioning re-sponse. Such a person, having experienced this conditioning, may become afraid when a dark sky appears, even if the severe storm is not immediately evident.
Trace Conditioning
The CS starts and terminates before the onset of the UCS. Presumably, the re-sponse is conditioned by the neutral trace of the conditioned stimulus, hence the name trace conditioning. With this conditioning, the CS is presented and terminated prior to the onset of the UCS. A parent who calls a child to dinner is using trace conditioning (Klein, 1996).
Backward Conditioning
This time relation also requires a brief examination. In backward conditioning, the UCS precedes the conditioned stimulus. Tait and Saladin (1986) indicated that backward conditioning may not produce the intended CS but may result in the development of another type of CR. The backward conditioning para-digm is a conditioned inhibition procedure, in which the CS is paired with the absence of the UCS. In some instances, a person would experience condi-tioned inhibition rather than condicondi-tioned excitation when exposed to the CS.
Extinction
As long as the conditioned and unconditioned stimuli are paired, the condi-tioned response is likely to occur, but if the condicondi-tioned stimuli is presented repeatedly without the unconditioned stimulus, the conditioned response gradually dissipates. This process is called extinction, and it continues until there is no longer any conditioned response.
When the organism no longer responds to the conditioned stimulus, it might appear that the effects of the conditioning process have been elimi-nated, but this is not usually the case; they have not. After a brief time, the CR reappears, though it is weaker. This phenomenon is called spontaneous recovery. To eliminate all the effects of the original conditioning, repeated ex-tinctions may be required.
Higher-Order Conditioning
An UCS is usually part of a stimulus-response reflexive unit that is pro-grammed within the nervous system. Pavlov’s experiment with his dog provides an excellent example of higher-order conditioning. After the dog had been conditioned to salivate at the sound of a bell, the bell was later
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rung in conjunction with a NS such as a flash of light. This NS would also elicit a salivation response, even though it had never been directly associ-ated with meat (Ormrod, 1999). The flash of light, through its association with the bell, eventually elicited the conditioned response. This process is called higher-order conditioning, and it consists of using a previous CS (the bell) as an UCS with which a new NS (the flash of light) can be paired to obtain another CS.
First-order conditioning is nothing more than the process of simultaneous, delayed, or trace conditioning. Second- or higher-order conditioning uses the CS from first-order conditioning as the UCS in a subsequent conditioning procedure. Pavlov has also demonstrated third-order conditioning, but this is extremely difficult to demonstrate. Third-order conditioning is difficult to ac-complish because of the ever-present possibility of extinction. When the CS is presented without the UCS, the CR is extinguished. Thus, when the light and the bell in Pavlov’s experiment are paired, the CR to the tone weakens because the original UCS (the electric shock) is absent. This tendency can be counteracted by interspersing trials of first-order conditioning (pairing of the bell with the flash of light), thereby strengthening the original CR. These dif-ficulties in obtaining higher-order conditioning underscore the limitations of classical conditioning: it cannot be separated very far from the unconditioned stimuli that comprise one half of the innately reflexive units (Ormrod, 1999).
Discrimination
Survival often requires a choice of alternative responses, and the ability to choose requires the ability to discriminate among objects and events in the environment. Such discrimination is easy to condition, even in as primitive an animal as the flatworm. Discrimination can be induced by prolonged training and by differential reinforcement. In prolonged training, a CS is paired with an UCS many times, and the subject develops a tendency to respond to addi-tional stimuli related to that CS. But for those stimuli not identical to the CS, the response level decreases. To increase the response level, the researcher uses differential reinforcement to induce discrimination by presenting the subject with a CS and, simultaneously, with an NS. Reinforcement follows only the CS, and when the researcher subsequently presents only the NS, the subject tends not to respond to it (Hergenhahn & Olson, 1997).
USING CLASSICAL CONDITIONING IN HUMAN LEARNING Principles of classical conditioning have been successfully used to control or condition human behaviors in the areas of involuntary responses and phobias
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(Brunner, Goodnow, & Austin, 1956). Involuntary responses can be induced through hunger. When animals or people are exposed to food, they exhibit a set of UCRs that prepare them to digest, metabolize, and store ingested foods.
These unconditioned digestion responses are involuntary and include the se-cretion of saliva, gastric juices, pancreatic enzymes, and insulin. Powley’s (1977) research confirmed that these unconditioned digestion responses in humans can be controlled.
Miller (1948) and Staats and Staats (1957) have reported the development of fear using classical conditioning in animals and humans. Their findings support the premise that fear is conditioned when a neutral stimulus (CS) is associated with an aversive event. An example given by Klein (1996) pro-vides some clarity to the above statement. He states that an academic evalu-ation is an aversive event and explains that when an individual takes a test (UCS), the examination elicits an unconditioned pain reaction (UCR). The psychological distress experienced when an instructor distributes a test is one aspect of a student’s pain reaction, and the increased physiological stress is another part of the response to receiving an examination. Although the inten-sity of the aversive event may decrease during the tests, students may not ex-perience relief until they have completed it.
More recently, Ormrod (1999) indicated that individuals who are unusually afraid of failing may have previously associated failure with unpleasant cir-cumstances, such as pain or other punishment. Educators should attempt to assure that this type of association with failure does not become such a strong CS for children that they resist engaging in new activities and attempting to solve challenging problems.
SUMMARY
Ivan Pavlov’s research in conditioning had a significant impact on the devel-opment of psychology. His experiments with salivation responses in dogs were instrumental in developing classical conditioning. The impact of his work received worldwide recognition. In 1904, he was awarded a Nobel Prize in Medicine and Physiology for his work on digestion (Smith, 1995).
Pavlov’s experiments have provided a theoretical framework for the con-tinuation of scientific studies in contemporary psychology and related med-ical research activities (Hollis, 1997). Additionally, his research in classmed-ical conditioning has led to understanding human fears and phobias and has pro-vided a model for educators to employ in reducing, controlling, or eliminat-ing fears and phobias, as well as in provideliminat-ing strategies for modifyeliminat-ing and controlling deviant behaviors.
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INTRODUCTION