What remains to be explained, once the stimulus–stimulus association theory has been accepted, is why the CR should occur and why it should take the form that it does. Pavlov’s dogs might ‘know’, by virtue of the CS–US link, that light and food go together, but this does not necessarily mean that the animal should start to salivate in response to the light. The most obvious explanation is that activation of the US (food) centre will evoke a given response, whether that activation is produced by presentation of the US (food) itself or, via the learned CS–US (light–food) connection, by presentation of the CS (light). An implication of this interpretation is that the CR and the UR should be the same, and this is true for the case just considered: the dog salivates (as a UR) to food and also comes to salivate (as a CR) to the light that has signalled food. In other examples of conditioning, however, the CR and UR are found to differ. In the autoshaping procedure, for instance, the UR is to approach and peck insid the food tray, whereas the CR that develops with training is to approach and peck at the light. In this case, the CR appears to be a blend of the behaviour that activation of the US (food) centre tends to evoke and the behaviour evoked by the CS (the light) itself. So we cannot say that the CR and the UR are always the same. There is, however, a simple rule that describes the relationship between them for most cases of conditioning, in that, as a result of classical conditioning, the animal generally comes to behave toward the CS (the light in these examples) as if it were the US (food). In other words, the CS (light) appears to take on some of the properties of the US (food) and to serve as an adequate substitute for it. So the unconditional response of a hungry animal is to approach food, probably salivating as it does so, and then to consume the food (by pecking, if the animal is a pigeon). The CR consists of directing these behaviour patterns toward the CS, in so far as the physical properties of the event used as the CS will allow this. This rule is sometimes referred to as the stimulus substitution hyphothesis. [stimulus substitution when the conditioned stimulus comes to acquire the same response-eliciting properties as the unconditioned stimulus]
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Showing posts with label UR. Show all posts
Showing posts with label UR. Show all posts
Thursday, December 2, 2010
PAVLOV’S CLASSICAL EXPERIMENT WITH DOGS
PAVLOV’S DOGS IN CLASSICAL EXPERIMENT
Pavlov spent the first half of his long scientific career working on the physiology of digestion, turning to the study of learning in about 1900. He had noticed that dogs which salivate copiously when given food also do so in response to other events – for example, at the approach of the laboratory attendant who supplied the food. This response was clearly acquired through experience. Pavlov (1927) took a version of this procedure into the laboratory, making it a model system that could be used to reveal basic principles of learning. Pavlov’s standard procedure involved a quiet, distraction-free laboratory, which gave the experimenter full control over events experienced by a lightly restrained dog. From time to time the dog was given access to food, and each presentation was accompanied (usually slightly preceded) by the occurrence of a neutral event, such as a flashing light. After several training trials (pairings of light and food), the dog would salivate at the flash of light, before any food had appeare.
Salivation at the presentation of food is called an unconditioned response (UR) [unconditioned response (UR) evoked by a stimulus before an animal has received any explicit training with that stimulus], since it occurs automatically (unconditionally). The food is an unconditioned stimulus (US)[unconditioned stimulus (US) evokes an unconditioned response]. The animal’s tendency to salivate when the light flashes is conditional on the light having been paired with food, so this is referred to as a conditioned response (CR)[conditioned response (CR) evoked by a conditioned stimulus as a result of classical conditioning] and the event that evokes it as a conditioned stimulus (CS)[conditioned stimulus (CS) evokes a conditioned response as a result of classical conditioning]. The whole training procedure was labelled conditioning. As other forms of training, introduced later, have also been described as conditioning, Pavlov’s version became known as classical conditioning.
[I.P. Pavlov (1849–1936), born the son of a priest in Ryazan (250 miles south-east of Moscow), moved in 1870 to study natural science and medicine in St Petersburg. He spent the rest of his life there conducting scientific research, first on the physiology of the digestive system (for which he was awarded a Nobel prize in 1904) and later on conditioned reflexes. Although the study of conditioned reflexes was taken up mostly by psychologists, Pavlov insisted that his approach as a physiologist was far superior to that adopted by the comparative psychologists of his day. His demonstration of the salivary conditioned reflex in dogs, for which he is widely known, was just the start of an extensive body of work, in which he analysed the conditioning process in detail, revealing phenomena and suggesting learning mechanisms that are still being actively investigated today.]
Pavlov spent the first half of his long scientific career working on the physiology of digestion, turning to the study of learning in about 1900. He had noticed that dogs which salivate copiously when given food also do so in response to other events – for example, at the approach of the laboratory attendant who supplied the food. This response was clearly acquired through experience. Pavlov (1927) took a version of this procedure into the laboratory, making it a model system that could be used to reveal basic principles of learning. Pavlov’s standard procedure involved a quiet, distraction-free laboratory, which gave the experimenter full control over events experienced by a lightly restrained dog. From time to time the dog was given access to food, and each presentation was accompanied (usually slightly preceded) by the occurrence of a neutral event, such as a flashing light. After several training trials (pairings of light and food), the dog would salivate at the flash of light, before any food had appeare.
Salivation at the presentation of food is called an unconditioned response (UR) [unconditioned response (UR) evoked by a stimulus before an animal has received any explicit training with that stimulus], since it occurs automatically (unconditionally). The food is an unconditioned stimulus (US)[unconditioned stimulus (US) evokes an unconditioned response]. The animal’s tendency to salivate when the light flashes is conditional on the light having been paired with food, so this is referred to as a conditioned response (CR)[conditioned response (CR) evoked by a conditioned stimulus as a result of classical conditioning] and the event that evokes it as a conditioned stimulus (CS)[conditioned stimulus (CS) evokes a conditioned response as a result of classical conditioning]. The whole training procedure was labelled conditioning. As other forms of training, introduced later, have also been described as conditioning, Pavlov’s version became known as classical conditioning.
[I.P. Pavlov (1849–1936), born the son of a priest in Ryazan (250 miles south-east of Moscow), moved in 1870 to study natural science and medicine in St Petersburg. He spent the rest of his life there conducting scientific research, first on the physiology of the digestive system (for which he was awarded a Nobel prize in 1904) and later on conditioned reflexes. Although the study of conditioned reflexes was taken up mostly by psychologists, Pavlov insisted that his approach as a physiologist was far superior to that adopted by the comparative psychologists of his day. His demonstration of the salivary conditioned reflex in dogs, for which he is widely known, was just the start of an extensive body of work, in which he analysed the conditioning process in detail, revealing phenomena and suggesting learning mechanisms that are still being actively investigated today.]
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