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64-600: The Pavlovian Society , also known as the Pavlovian Society of North America , is a learned society dedicated to advancing Pavlovian psychological research, and to promoting the exchange of ideas between scientific disciplines . The Pavlovian Society was established in 1955 by W. Horsley Gantt , at a ceremony held to commemorate the 25th anniversary of the founding of his Pavlovian Laboratory at Johns Hopkins School of Medicine in Baltimore , Maryland . On May 7, 1955, at

128-524: A nervous system . A reflex occurs via neural pathways in the nervous system called reflex arcs . A stimulus initiates a neural signal, which is carried to a synapse . The signal is then transferred across the synapse to a motor neuron , which evokes a target response. These neural signals do not always travel to the brain, so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought. Many reflexes are fine-tuned to increase organism survival and self-defense. This

192-414: A CS than it does for a novel stimulus to become a CS, when the stimulus is paired with an effective US. This is one of the most common ways to measure the strength of learning in classical conditioning. A typical example of this procedure is as follows: a rat first learns to press a lever through operant conditioning . Then, in a series of trials, the rat is exposed to a CS, a light or a noise, followed by

256-546: A US through forward conditioning. Then a second neutral stimulus ("CS2") is paired with the first (CS1) and comes to yield its own conditioned response. For example: A bell might be paired with food until the bell elicits salivation. If a light is then paired with the bell, then the light may come to elicit salivation as well. The bell is the CS1 and the food is the US. The light becomes the CS2 once it

320-498: A US. A compound CS (CS1+CS2) is paired with a US. A separate test for each CS (CS1 and CS2) is performed. The blocking effect is observed in a lack of conditional response to CS2, suggesting that the first phase of training blocked the acquisition of the second CS. [REDACTED] Experiments on theoretical issues in conditioning have mostly been done on vertebrates , especially rats and pigeons. However, conditioning has also been studied in invertebrates , and very important data on

384-462: A dog's saliva produced as a CR differed in composition from that produced as a UR. The CR is sometimes even the opposite of the UR. For example: the unconditional response to electric shock is an increase in heart rate, whereas a CS that has been paired with the electric shock elicits a decrease in heart rate. (However, it has been proposed that only when the UR does not involve the central nervous system are

448-496: A negative associate strength) then R-W predicts that the CS will not undergo extinction (its V will not decrease in size). The most important and novel contribution of the R–W model is its assumption that the conditioning of a CS depends not just on that CS alone, and its relationship to the US, but also on all other stimuli present in the conditioning situation. In particular, the model states that

512-424: A number of synapses in a number of different nuclei in the central nervous system (e.g., the escape reflex ). Others of these involve just a couple of synapses to function (e.g., the withdrawal reflex ). Processes such as breathing , digestion , and the maintenance of the heartbeat can also be regarded as reflex actions, according to some definitions of the term. In medicine , reflexes are often used to assess

576-469: A peripheral problem, and lively or exaggerated reflexes a central one. A stretch reflex is the contraction of a muscle in response to its lengthwise stretch. While the reflexes above are stimulated mechanically, the term H-reflex refers to the analogous reflex stimulated electrically, and tonic vibration reflex for those stimulated to vibration. A tendon reflex is the contraction of a muscle in response to striking its tendon . The Golgi tendon reflex

640-404: A piece of cardboard. A key idea behind the R–W model is that a CS signals or predicts the US. One might say that before conditioning, the subject is surprised by the US. However, after conditioning, the subject is no longer surprised, because the CS predicts the coming of the US. (The model can be described mathematically and that words like predict, surprise, and expect are only used to help explain

704-501: A procedure that enabled him to study the digestive processes of animals over long periods of time. He redirected the animals' digestive fluids outside the body, where they could be measured. Pavlov noticed that his dogs began to salivate in the presence of the technician who normally fed them, rather than simply salivating in the presence of food. Pavlov called the dogs' anticipatory salivation "psychic secretion". Putting these informal observations to an experimental test, Pavlov presented

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768-512: A puff of air directed at a person's eye could be followed by the sound of a buzzer. In temporal conditioning, a US is presented at regular intervals, for instance every 10 minutes. Conditioning is said to have occurred when the CR tends to occur shortly before each US. This suggests that animals have a biological clock that can serve as a CS. This method has also been used to study timing ability in animals (see Animal cognition ). The example below shows

832-419: A replica of the unconditioned response, but Pavlov noted that saliva produced by the CS differs in composition from that produced by the US. In fact, the CR may be any new response to the previously neutral CS that can be clearly linked to experience with the conditional relationship of CS and US. It was also thought that repeated pairings are necessary for conditioning to emerge, but many CRs can be learned with

896-428: A single trial, especially in fear conditioning and taste aversion learning. Learning is fastest in forward conditioning. During forward conditioning, the onset of the CS precedes the onset of the US in order to signal that the US will follow. Two common forms of forward conditioning are delay and trace conditioning. [REDACTED] During simultaneous conditioning, the CS and US are presented and terminated at

960-413: A stimulus (e.g. the sound of a metronome ) and then gave the dog food; after a few repetitions, the dogs started to salivate in response to the stimulus. Pavlov concluded that if a particular stimulus in the dog's surroundings was present when the dog was given food then that stimulus could become associated with food and cause salivation on its own. In Pavlov's experiments the unconditioned stimulus (US)

1024-441: A type of nervous system that is more recent in terms of evolutionary development. There are autonomic reflexes and skeletal, somatic reflexes. The myotatic or muscle stretch reflexes (sometimes known as deep tendon reflexes ) provide information on the integrity of the central nervous system and peripheral nervous system . This information can be detected using electromyography (EMG) . Generally, decreased reflexes indicate

1088-444: A weak stimulus is presented. During acquisition, the CS and US are paired as described above. The extent of conditioning may be tracked by test trials. In these test trials, the CS is presented alone and the CR is measured. A single CS-US pairing may suffice to yield a CR on a test, but usually a number of pairings are necessary and there is a gradual increase in the conditioned response to the CS. This repeated number of trials increase

1152-434: Is a basic behavioral mechanism, and its neural substrates are now beginning to be understood. Though it is sometimes hard to distinguish classical conditioning from other forms of associative learning (e.g. instrumental learning and human associative memory ), a number of observations differentiate them, especially the contingencies whereby learning occurs. Together with operant conditioning , classical conditioning became

1216-460: Is even reversed. This prevents resistance reflexes from impeding movements. The underlying sites and mechanisms of reflex modulation are not fully understood. There is evidence that the output of sensory neurons is directly modulated during behavior—for example, through presynaptic inhibition . The effect of sensory input upon motor neurons is also influenced by interneurons in the spinal cord or ventral nerve cord and by descending signals from

1280-439: Is observed in reflexes such as the startle reflex , which provides an automatic response to an unexpected stimulus, and the feline righting reflex , which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a single synapse, or junction, in the signaling pathway. Long-latency reflexes produce nerve signals that are transduced across multiple synapses before generating

1344-493: Is paired with a US until asymptotic CR levels are reached. CS+/US trials are continued, but these are interspersed with trials on which the CS+ is paired with a second CS, (the CS-) but not with the US (i.e. CS+/CS- trials). Typically, organisms show CRs on CS+/US trials, but stop responding on CS+/CS− trials. This form of classical conditioning involves two phases. A CS (CS1) is paired with

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1408-401: Is paired with the CS1. [REDACTED] Backward conditioning occurs when a CS immediately follows a US. Unlike the usual conditioning procedure, in which the CS precedes the US, the conditioned response given to the CS tends to be inhibitory. This presumably happens because the CS serves as a signal that the US has ended, rather than as a signal that the US is about to appear. For example,

1472-481: Is repeated the organism exhibits a conditioned response (CR) to the conditioned stimulus when the conditioned stimulus is presented alone. (A conditioned response may occur after only one pairing.) Thus, unlike the UR, the CR is acquired through experience, and it is also less permanent than the UR. Usually the conditioned response is similar to the unconditioned response, but sometimes it is quite different. For this and other reasons, most learning theorists suggest that

1536-402: Is the inverse of a stretch reflex. Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes . These automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place. They include: Other reflexes found in the central nervous system include: Many of these reflexes are quite complex, requiring

1600-400: Is the response to the conditioned stimulus, whereas the unconditioned response (UR) corresponds to the unconditioned stimulus. Pavlov reported many basic facts about conditioning; for example, he found that learning occurred most rapidly when the interval between the CS and the appearance of the US was relatively short. As noted earlier, it is often thought that the conditioned response is

1664-446: The false consensus effect . Classical conditioning occurs when a conditioned stimulus (CS) is paired with an unconditioned stimulus (US). Usually, the conditioned stimulus is a neutral stimulus (e.g., the sound of a tuning fork ), the unconditioned stimulus is biologically potent (e.g., the taste of food) and the unconditioned response (UR) to the unconditioned stimulus is an unlearned reflex response (e.g., salivation). After pairing

1728-420: The CR and the UR opposites.) The Rescorla–Wagner (R–W) model is a relatively simple yet powerful model of conditioning. The model predicts a number of important phenomena, but it also fails in important ways, thus leading to a number of modifications and alternative models. However, because much of the theoretical research on conditioning in the past 40 years has been instigated by this model or reactions to it,

1792-424: The CR is said to be "extinguished." [REDACTED] External inhibition may be observed if a strong or unfamiliar stimulus is presented just before, or at the same time as, the CS. This causes a reduction in the conditioned response to the CS. Several procedures lead to the recovery of a CR that had been first conditioned and then extinguished. This illustrates that the extinction procedure does not eliminate

1856-415: The CS and the US causes a gradual increase in the associative strength of the CS. This increase is determined by the nature of the US (e.g. its intensity). The amount of learning that happens during any single CS-US pairing depends on the difference between the total associative strengths of CS and other stimuli present in the situation (ΣV in the equation), and a maximum set by the US (λ in the equation). On

1920-456: The CS. As a result of this "surprising" outcome, the associative strength of the CS takes a step down. Extinction is complete when the strength of the CS reaches zero; no US is predicted, and no US occurs. However, if that same CS is presented without the US but accompanied by a well-established conditioned inhibitor (CI), that is, a stimulus that predicts the absence of a US (in R-W terms, a stimulus with

1984-416: The CS. In the equation, V represents the current associative strength of the CS, and ∆V is the change in this strength that happens on a given trial. ΣV is the sum of the strengths of all stimuli present in the situation. λ is the maximum associative strength that a given US will support; its value is usually set to 1 on trials when the US is present, and 0 when the US is absent. α and β are constants related to

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2048-461: The Rescorla-Wagner equation. It specifies the amount of learning that will occur on a single pairing of a conditioning stimulus (CS) with an unconditioned stimulus (US). The above equation is solved repeatedly to predict the course of learning over many such trials. In this model, the degree of learning is measured by how well the CS predicts the US, which is given by the "associative strength" of

2112-416: The R–W model deserves a brief description here. The Rescorla-Wagner model argues that there is a limit to the amount of conditioning that can occur in the pairing of two stimuli. One determinant of this limit is the nature of the US. For example: pairing a bell with a juicy steak is more likely to produce salivation than pairing the bell with a piece of dry bread, and dry bread is likely to work better than

2176-402: The US is fully predicted, the associative strength of the CS stops growing, and conditioning is complete. The associative process described by the R–W model also accounts for extinction (see "procedures" above). The extinction procedure starts with a positive associative strength of the CS, which means that the CS predicts that the US will occur. On an extinction trial the US fails to occur after

2240-411: The US is predicted by the sum of the associative strengths of all stimuli present in the conditioning situation. Learning is controlled by the difference between this total associative strength and the strength supported by the US. When this sum of strengths reaches a maximum set by the US, conditioning ends as just described. The R–W explanation of the blocking phenomenon illustrates one consequence of

2304-516: The US, a mild electric shock. An association between the CS and US develops, and the rat slows or stops its lever pressing when the CS comes on. The rate of pressing during the CS measures the strength of classical conditioning; that is, the slower the rat presses, the stronger the association of the CS and the US. (Slow pressing indicates a "fear" conditioned response, and it is an example of a conditioned emotional response; see section below.) Typically, three phases of conditioning are used. A CS (CS+)

2368-418: The US, but the US also occurs at other times. If this occurs, it is predicted that the US is likely to happen in the absence of the CS. In other words, the CS does not "predict" the US. In this case, conditioning fails and the CS does not come to elicit a CR. This finding – that prediction rather than CS-US pairing is the key to conditioning – greatly influenced subsequent conditioning research and theory. In

2432-406: The acquisition of any new behavior, but rather the tendency to respond in old ways to new stimuli. Thus, he theorized that the CS merely substitutes for the US in evoking the reflex response. This explanation is called the stimulus-substitution theory of conditioning. A critical problem with the stimulus-substitution theory is that the CR and UR are not always the same. Pavlov himself observed that

2496-490: The analogy of a mechanical statue to explain how sensory input could trigger motor responses in a deterministic and automatic manner. The term "reflex" was introduced in the 19th century by the English physiologist Marshall Hall , who is credited with formulating the concept of reflex action and explaining it scientifically. He introduced the term to describe involuntary movements triggered by external stimuli, which are mediated by

2560-465: The association of stimuli as described above, whereas in operant conditioning behaviors are modified by the effect they produce (i.e., reward or punishment). The best-known and most thorough early work on classical conditioning was done by Ivan Pavlov , although Edwin Twitmyer published some related findings a year earlier. During his research on the physiology of digestion in dogs, Pavlov developed

2624-423: The assumption just stated. In blocking (see "phenomena" above), CS1 is paired with a US until conditioning is complete. Then on additional conditioning trials a second stimulus (CS2) appears together with CS1, and both are followed by the US. Finally CS2 is tested and shown to produce no response because learning about CS2 was "blocked" by the initial learning about CS1. The R–W model explains this by saying that after

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2688-459: The brain. Breathing can also be considered both involuntary and voluntary, since breath can be held through internal intercostal muscles . The concept of reflexes dates back to the 17th century with René Descartes . Descartes introduced the idea in his work " Treatise on Man ", published posthumously in 1664. He described how the body could perform actions automatically in response to external stimuli without conscious thought. Descartes used

2752-560: The conclusion of the 25th anniversary ceremony, the Society's first meeting was held. The meeting was attended by Gantt, Howard Liddell , Edward Kempf, David Rioch , and William G. Reese. The agreement reached at that meeting was for the society's membership to be initially limited to thirty-five people. Early in its history, the Pavlovian Society held its annual meetings in or near Baltimore and/or New York City , but this began to change as

2816-526: The conditioned stimulus comes to signal or predict the unconditioned stimulus, and go on to analyse the consequences of this signal. Robert A. Rescorla provided a clear summary of this change in thinking, and its implications, in his 1988 article "Pavlovian conditioning: It's not what you think it is". Despite its widespread acceptance, Rescorla's thesis may not be defensible. Classical conditioning differs from operant or instrumental conditioning : in classical conditioning, behaviors are modified through

2880-413: The effect of conditioning. These procedures are the following: Stimulus generalization is said to occur if, after a particular CS has come to elicit a CR, a similar test stimulus is found to elicit the same CR. Usually the more similar the test stimulus is to the CS the stronger the CR will be to the test stimulus. Conversely, the more the test stimulus differs from the CS, the weaker the CR will be, or

2944-490: The experimental results in 1897. In the study of digestion , Pavlov observed that the experimental dogs salivated when fed red meat. Pavlovian conditioning is distinct from operant conditioning (instrumental conditioning), through which the strength of a voluntary behavior is modified, either by reinforcement or by punishment . However, classical conditioning can affect operant conditioning; classically conditioned stimuli can reinforce operant responses. Classical conditioning

3008-580: The extinction procedure, the CS is presented repeatedly in the absence of a US. This is done after a CS has been conditioned by one of the methods above. When this is done, the CR frequency eventually returns to pre-training levels. However, extinction does not eliminate the effects of the prior conditioning. This is demonstrated by spontaneous recovery – when there is a sudden appearance of the (CR) after extinction occurs – and other related phenomena (see "Recovery from extinction" below). These phenomena can be explained by postulating accumulation of inhibition when

3072-426: The first pairing of the CS and US, this difference is large and the associative strength of the CS takes a big step up. As CS-US pairings accumulate, the US becomes more predictable, and the increase in associative strength on each trial becomes smaller and smaller. Finally, the difference between the associative strength of the CS (plus any that may accrue to other stimuli) and the maximum strength reaches zero. That is,

3136-468: The foundation of behaviorism , a school of psychology which was dominant in the mid-20th century and is still an important influence on the practice of psychological therapy and the study of animal behavior. Classical conditioning has been applied in other areas as well. For example, it may affect the body's response to psychoactive drugs , the regulation of hunger, research on the neural basis of learning and memory, and in certain social phenomena such as

3200-542: The health of the nervous system . Doctors will typically grade the activity of a reflex on a scale from 0 to 4. While 2+ is considered normal, some healthy individuals are hypo-reflexive and register all reflexes at 1+, while others are hyper-reflexive and register all reflexes at 3+. Depending on where you are, another way of grading is from –4 (absent) to +4 (clonus), where 0 is "normal". Some might imagine that reflexes are immutable. In reality, however, most reflexes are flexible and can be substantially modified to match

3264-466: The initial conditioning, CS1 fully predicts the US. Since there is no difference between what is predicted and what happens, no new learning happens on the additional trials with CS1+CS2, hence CS2 later yields no response. Reflex In biology , a reflex , or reflex action , is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus . Reflexes are found with varying levels of complexity in organisms with

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3328-400: The model.) Here the workings of the model are illustrated with brief accounts of acquisition, extinction, and blocking. The model also predicts a number of other phenomena, see main article on the model. Δ V = α β ( λ − Σ V ) {\displaystyle \Delta V=\alpha \beta (\lambda -\Sigma V)} This is

3392-417: The more it will differ from that previously observed. One observes stimulus discrimination when one stimulus ("CS1") elicits one CR and another stimulus ("CS2") elicits either another CR or no CR at all. This can be brought about by, for example, pairing CS1 with an effective US and presenting CS2 with no US. Latent inhibition refers to the observation that it takes longer for a familiar stimulus to become

3456-467: The neural basis of conditioning has come from experiments on the sea slug, Aplysia . Most relevant experiments have used the classical conditioning procedure, although instrumental (operant) conditioning experiments have also been used, and the strength of classical conditioning is often measured through its operant effects, as in conditioned suppression (see Phenomena section above) and autoshaping . According to Pavlov, conditioning does not involve

3520-418: The reflex response. Reflex is an anatomical concept and it refers to a loop consisting, in its simplest form, of a sensory nerve, the input, and a motor nerve, the output. Autonomic does not mean automatic. The term autonomic is an anatomical term and it refers to a type of nervous system in animals and humans that is very primitive. Skeletal or somatic are, similarly, anatomical terms that refer to

3584-406: The requirements of the behavior in both vertebrates and invertebrates. A good example of reflex modulation is the stretch reflex . When a muscle is stretched at rest, the stretch reflex leads to contraction of the muscle, thereby opposing stretch (resistance reflex). This helps to stabilize posture. During voluntary movements, however, the intensity (gain) of the reflex is reduced or its sign

3648-400: The salience of the CS and the speed of learning for a given US. How the equation predicts various experimental results is explained in following sections. For further details, see the main article on the model. The R–W model measures conditioning by assigning an "associative strength" to the CS and other local stimuli. Before a CS is conditioned it has an associative strength of zero. Pairing

3712-429: The same time. For example: If a person hears a bell and has air puffed into their eye at the same time, and repeated pairings like this led to the person blinking when they hear the bell despite the puff of air being absent, this demonstrates that simultaneous conditioning has occurred. [REDACTED] Second-order or higher-order conditioning follow a two-step procedure. First a neutral stimulus ("CS1") comes to signal

3776-437: The society began to attract more members from other countries. John J. Furedy , a former president of the society, claimed that it was unique among psychological learned societies in being truly open to "genuine debate and discussion", which he argued was representative of a pre-Socratic philosophy. Gantt was the founding president of the Pavlovian Society, serving from 1955 to 1965. Other people who have served as president of

3840-571: The society since then include Stephen Maren , Michael Fanselow , Richard F. Thompson , and B. F. Skinner . The current president is Natalie Tronson in the Department of Psychology at the University of Michigan. This article about a scientific organization is a stub . You can help Misplaced Pages by expanding it . Pavlovian The Russian physiologist Ivan Pavlov studied classical conditioning with detailed experiments with dogs, and published

3904-660: The spinal cord and the nervous system, distinct from voluntary movements controlled by the brain. Hall's significant work on reflex function was detailed in his 1833 paper, "On the Reflex Function of the Medulla Oblongata and Medulla Spinalis," published in the Philosophical Transactions of the Royal Society , where he provided a clear account of how reflex actions were mediated by the spinal cord, independent of

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3968-418: The strength and/or frequency of the CR gradually. The speed of conditioning depends on a number of factors, such as the nature and strength of both the CS and the US, previous experience and the animal's motivational state. The process slows down as it nears completion. If the CS is presented without the US, and this process is repeated often enough, the CS will eventually stop eliciting a CR. At this point

4032-403: The temporal conditioning, as US such as food to a hungry mouse is simply delivered on a regular time schedule such as every thirty seconds. After sufficient exposure the mouse will begin to salivate just before the food delivery. This then makes it temporal conditioning as it would appear that the mouse is conditioned to the passage of time. [REDACTED] In this procedure, the CS is paired with

4096-477: Was the food because its effects did not depend on previous experience. The metronome's sound is originally a neutral stimulus (NS) because it does not elicit salivation in the dogs. After conditioning, the metronome's sound becomes the conditioned stimulus (CS) or conditional stimulus; because its effects depend on its association with food. Likewise, the responses of the dog follow the same conditioned-versus-unconditioned arrangement. The conditioned response (CR)

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