Chapter 3 - Pavlovian Conditioning Flashcards
(36 cards)
Describe Pavlov’s early life, career path, and other factors that led him to study the digestive processes and the salivary reflex in the dog. When did Pavlov become interested in psychic reflexes? (pp. 57–60)
Pavlov started his career with research on the circulatory system and then moved on to the physiology of digestion. He developed special surgical procedures that enabled him to study the digestive processes of animals over long periods of time by redirecting an animal’s digestive fluids outside the body, where they could be measured.
What were the psychic secretions that became a focus of Pavlov’s work? Why did Pavlov shift the focus of his work from digestive processes to psychic secretions? (p. 59)
When a dog had been fed a number of times, it began to salivate before anything was put into its mouth. In fact, it might start salivating as soon as it entered the laboratory. Pavlov, like others of his day, assumed that these “psychic secretions” were caused by the thoughts, memories, or wishes of the animal.
What fascinated Pavlov was that the dogs did not salivate when they were first brought into the laboratory, but only after they had been fed there repeatedly. How could this be? How could experience alter the action of a gland?
Describe Pavlov’s work with dogs that illustrates Pavlovian conditioning. Define unconditional reflexes, conditional reflexes, unconditional stimulus, unconditional response, conditional stimulus, and conditional response. What terms are used in place of these? (pp. 60–62)
Comment: In describing Pavlovian conditioning, it is customary to also speak of another type of stimulus, a neutral stimulus. Chance de-emphasizes the neutral stimulus in his treatment of the topic. (He does mention it on page 61 but does not include it in his diagrams of classical conditioning and does not include it as a critical term.) The neutral stimulus is simply a way of describing the conditional stimulus before it is able to elicit the conditional response. For example, the author describes the use of a hand clap as a conditional stimulus (p. 61). We would refer to the hand clap as a neutral stimulus before it could elicit the conditional response, salivation. In this unit’s conceptual exercise, you will be asked to identify the neutral stimulus in examples of Pavlovian conditioning.
For our purposes, we will consider a stimulus to be neutral if it does not elicit a particular conditioned or unconditioned response. For example, a bright light does not elicit eye blinks, so it is a neutral stimulus with respect to the eye-blink response. However, bright light does elicit pupil contraction, so bright light would be an unconditioned stimulus (not a neutral stimulus) for the pupil-contraction response.
Unconditional Reflex: A reflex that occurs naturally: a dog that salivates when food is put into its mouth.
Conditional Reflex: A reflex that is acquired through experience: a dog that salivates at the sound of the footsteps of the person who feeds it.
An unconditional reflex consists of an unconditional stimulus (US) and the behavior it evokes, the unconditional response (UR). Meat and salivation.
A conditional reflex consists of a conditional stimulus (CS) and the behavior it reliably evokes, the conditional response (CR). When the sight of a food dish regularly evokes salivation, the food dish is a CS and salivating is a CR:
The neutral stimulus is simply a way of describing the conditional stimulus before it is able to elicit the conditional response.
Describe Wallace and Rosen’s demonstration (2000) that rats show a strong response to an odorous chemical derived from fox feces. How does this assist in survival? (pp. 60–61)
Karin Wallace and Jeffrey Rosen (2000) demonstrated that rats show a strong unconditional fear response to an odorous chemical derived from fox feces. As the authors note, “In the wild, when a rat is attacked by a predator, it is usually . . . too late for defensive maneuvers.” Thus the rat that has an innate tendency to freeze or run away when it detects odors associated with its enemies has a better chance of avoiding those enemies.
Is the presentation of the two stimuli (i.e., the neutral stimulus and the unconditional stimulus) independent of the behaviour of the animal? Explain. Provide an original example illustrating that an organism whose behaviour is subject to Pavlovian conditioning is more likely to survive than an organism whose behaviour is not subject to such conditioning. (p. 63)
The appearance of the two stimuli is independent of behavior; the CS and the US are presented regardless of what the animal or person does.
Define higher-order Pavlovian conditioning. Describe Frolov’s demonstration of higher-order conditioning. Why does higher-order conditioning increase the importance of Pavlovian conditioning? (pp. 63–64) Describe Graham and Desjardins’ (1980) study in which the experimenters used Pavlovian conditioning to influence the mating behaviour of male rats. (pp. 63–64)
Comment: Chance uses higher-order conditioning to refer to the use of a previously established conditional stimulus to function as an unconditional stimulus in Pavlovian conditioning. In this unit’s conceptual exercise, we refer to one form of higher-order conditioning as second-order conditioning. In second-order conditioning, the CS (CS-0) predicts another previously established CS (CS-1). The CS-1 obtained its ability to elicit a CR because it was paired with a US for a UR.
In third-order conditioning, a CS-0 is paired with a CS-1 that gained its ability to elicit a response by being paired with a previously established CS (CS-2), whereas CS-2 gained its eliciting function by being paired with a US. As such, when we refer to second-order or third-order conditioning, we are referring to the number of steps that the CS is removed from a US. Although second-order conditioning can be quite effective, third-order conditioning (and further removed orders) have not generally been demonstrated to be very potent forms of conditioning. Fifth-order conditioning has been noted if the US is a shock, but generally the further away you get from the pairing with the US, the weaker the CR is likely to be.
The basic Pavlovian procedure, as you have seen, consists of presenting a neutral stimulus followed by an unconditional stimulus. Suppose, however, that a neutral stimulus precedes a well-established CS. The CS is not a US, yet thanks to conditioning it does elicit a CR. So, if you paired a neutral stimulus with the CS, would the neutral stimulus become another CS?
G. P. Frolov, who worked in Pavlov’s lab, decided to find out. First he trained a dog to salivate at the sound of a ticking metronome by following the ticking with food. When the metronome was well established as a CS for salivating, Frolov held up a black square and then activated the metronome:
At first the dog salivated at the sound of the metronome but not at the sight of the black square. After several pairings of the two stimuli, how-ever, the dog began salivating when it saw the square. The black square had become a CS for salivating even though it had never been followed by food:
The procedure of pairing a neutral stimulus with a well-established CS is called higher-order conditioning.
Higher-order conditioning greatly increases the importance of Pavlovian conditioning because it means that many more stimuli can come to elicit conditional responses.
physiologists J. M. Graham and Claude Desjardins (1980) demonstrated that a male rat that responds to a sexually receptive female by increasing the level of certain hormones will respond in a similar manner to an odor that has been paired with a receptive female. Thanks to higher-order conditioning, a neutral stimulus be- came a CS by being paired with the odor, without its ever having been paired with a receptive female. This might give the rat a reproductive ad- vantage in the wild: The rat that responds to a stimulus associated with the female’s scent has an advantage over the rat that responds only to her scent.
Describe Staats and Staats’ (1957) classic experiment of verbal higher-order conditioning. (pp. 63–64)
In one classic experiment, Carolyn and Arthur Staats (1957) asked college students to look at nonsense syllables such as YOF, LAJ, and QUG as they were flashed on a screen. At the same time, the students repeated words spoken by the experimenters. For some students, the experimenters paired the syllable YOF with positive words such as beauty, gift, and win, and the syllable XEH with negative words such as thief, sad, and enemy. For other students, the associations were reversed: XEH was paired with positive words, YOF with negative ones. (Notice that no US was ever presented.) After this, the students rated each nonsense syllable on a seven-point scale ranging from unpleasant to pleasant. The results indicated that the nonsense syllables came to elicit emotional responses similar to the emotional value of the words with which they had been paired.
How can response latency be used to measure Pavlovian conditioning? How is the use of latency as a measure of Pavlovian conditioning problematic? (pp. 65–66)
Given that the US is by definition capable of evoking the UR, how is it possible to tell when learning occurs? One answer is to note when salivation begins. If the dog begins salivating after the CS begins but before the presentation of the US, conditioning has occurred. In this case, you can measure the amount of learning in terms of the latency of the response - the interval between the onset of the CS and the first appearance of saliva. As the number of CS–US pairings increases, the response latency diminishes; the dog may begin salivating even before the tone stops sounding.
In some conditioning studies, the interval between CS onset and the appearance of the US is so short that using response latency as a measure of learning is difficult.
Describe the use of test trials to measure Pavlovian conditioning. Provide an original example of this use of test trials. (p. 65)
Test trials involve presenting the CS alone (i.e., without the US) periodically, perhaps on every fifth trial.
When test trials are used, the number of CRs in a block of, say, ten test trials is plotted on a curve. Learning is thus represented as an increase in the frequency of the conditional response.
Describe the method of measuring Pavlovian conditioning by means of intensity or amplitude of the CR. Provide an original example. (p. 65)
Another way to measure Pavlovian learning is to measure the intensity or strength (sometimes called amplitude) of the CR. Pavlov found that the first CRs are apt to be very weak (a drop or two of saliva), but with repeated trials, the saliva flow in response to the CS increases rapidly. The increase in the number of drops of saliva is a measure of learning.
Define pseudoconditioning, and explain why it poses a problem in measuring Pavlovian conditioning. How can researchers overcome this problem? (pp. 65–66)
One problem in attempting to measure Pavlovian learning is a phenomenon known as pseudoconditioning. Pseudoconditioning is the tendency of a neutral stimulus to elicit a CR after a US has elicited a reflex response. For example, suppose a nurse coughs just as he gives you a painful injection. When you receive the injection, you wince. Now suppose that after the injection, the nurse coughs again. Very likely you will wince again, just as you did when you received the injection. You might think conditioning has occurred - the cough appears to have become a conditional stimulus for wincing. But you might be mistaken. A strong stimulus, such as a needle jab, can sensitize you to other stimuli so that you react to them more or less as you would react to the strong stimulus. If a nurse jabs you with a needle, you may then wince when he coughs, even if he did not cough before jabbing you. You wince, not because conditioning has occurred, but because the needle jab has sensitized you to other stimuli.
Describe the following four ways of pairing the CS and the US in Pavlovian conditioning: trace conditioning, delayed conditioning, simultaneous conditioning, and backward conditioning. Specify the relative effectiveness of each of these procedures. Be able to provide and recognize original examples of each. (pp. 66–69)
In trace conditioning, the CS begins and ends before the US appears. There is, then, a gap between the two stimuli. Trace conditioning gets its name from the assumption that the CS leaves some sort of neural trace.
In delay conditioning, the CS and US overlap. That is, the US appears be- fore the CS disappears. To apply the delay procedure to eyelid conditioning, we might sound a buzzer for 5 seconds and sometime during this period, we might send a puff of air into the person’s eye. As in trace conditioning, the CS appears before the US; the difference is that in the delay procedure the CS and US overlap.
In simultaneous conditioning, the CS and US coincide exactly.
Simultaneous conditioning is a weak procedure for establishing a conditional response.
In backward conditioning, the CS follows the US. It is very difficult to produce a CR with the backward procedure.
Because of the relative ineffectiveness of simultaneous and backward procedures, they are seldom used in studies of Pavlovian conditioning, but it’s interesting to note that ad agencies often use simultaneous and backward conditioning
What is a contingency? Describe Rescorla’s (1968) experiment that demonstrated the importance of the CS-US contingency in the effectiveness of Pavlovian conditioning. In everyday life, do we generally encounter high or medium-low degrees of contingency between the CS and the US? Explain. (p. 69)
Comment: At one time, scientists thought that the critical factor in establishing the strength of a CS (i.e., the ability of the CS to elicit a strong CR) was the number of times the CS was paired with the US. For example, a tone could be best established as a CS for an eye-blink response through a large number of pairings of the tone with a puff of air, a US for the eye-blink response.
However, two additional factors affect the strength of the CS, both of which are part of the contingency factor. The contingency factor consists of two probabilities: the probabilities that 1) the US will be presented after the CS and 2) the US will be presented in absence of the CS.
As such, the strength of our CS (tone) would increase if (a) the puff presentation followed every presentation of the tone and (b) the puff was never presented alone (i.e., in absence of the tone). Consider the extent to which presenting the CS “predicts” the presentation of the US. We say that the CS predicts the US if (a) the CS is always followed by the US—the puff—and (b) the absence of the CS is followed by the absence of the US.
The importance of the CS “predicting” the US may also be illustrated in the following applied example.
Ed is an average-sized hockey player who is beaten up by the league hit man “Moose” Gantua. In this case, the US would be the painful stimuli involved in being beaten; the UR and CR would be Ed’s fear reaction, and the CS would be the sight of Moose to Ed. We are concerned with how strong Ed’s fear reaction would be when he sees Moose (i.e., how strong would the CR be to the CS?).
As we have said, the magnitude of the CR to the CS would be most importantly influenced by the extent to which the CS predicts the occurrence of the CR. As such, Ed’s fear would be greatest if (a) the sight of Moose (the CS) was always followed by a beating (the US) and (b) beatings (the US) were only delivered by Moose (i.e., the US never occurred unless it preceded (predicted) the CS. In contrast, Ed’s fear at the sight of Moose (the CS) would be decreased in magnitude if (a) the sight of Moose (the CS) was not always followed by a beating (the US) or if (b) Ed was beaten by bullies other than Moose—in which case the S would also occur in absence of the CS (the sight of Moose).
A contingency is an if–then statement. One event, X, is contingent on another event, Y, to the extent that X occurs if and only if Y occurs.
Various experiments have suggested that the effectiveness of Pavlovian procedures varies with the degree of contingency between CS and US. In one study, Robert Rescorla (1968) exposed rats to a tone followed by a mild shock. Although all the rats received the same number of CS–US pairings, in additional trials the US sometimes appeared alone. In one group, the shock occurred without the CS in 10% of the additional trials; in a second group, the US appeared alone in 20% of the trials; and in a third group, the US appeared alone in 40% of the trials. The results showed that the amount of learning depended on how reliably the CS predicted shock. When the CS was nearly always followed by the US, conditioning occurred. When a shock was about as likely to occur in the absence of a CS as in its presence (the 40% group), little or no learning took place.
Medium to low.
Outside the laboratory, however, life is more complicated. A stimulus will sometimes precede a particular US and other times will appear alone - or, to be more precise, it will appear with stimuli other than the US.
What is CS-US contiguity, and how does this contiguity influence the effectiveness of classical conditioning? Does the type of response being conditioned influence CS-US contiguity? Explain, citing an example from the text. Are short intervals or long intervals (between the CS and the US) more effective in Pavlovian conditioning? (pp. 69–70)
Contiguity refers to the closeness in time or space between two events. In Pavlovian conditioning, contiguity usually refers to the interval between the CS and US. This interval is called the interstimulus interval (ISI).
In trace conditioning, the ISI is the interval between the termination of the CS and the onset of the US; in delay conditioning, where the two stimuli over- lap, it refers to the interval between the onset of the CS and the onset of the US. In general, the shorter the ISI, the more quickly conditioning occurs. However, the simultaneous procedure, with no interval at all, is ineffective.
One important variable is the kind of response being learned. For instance, in establishing a conditional eyeblink response, the ideal CS–US interval is usually less than one-half second. In fear conditioning, in which a stimulus is paired with a stimulus that arouses fear, the ISI may be much longer, perhaps several minutes. And it is possible to obtain very good results with long CS–US intervals in studies of taste aversion. Taste aversion conditioning usually consists of pairing a distinctive taste with a substance that induces nausea. Some researchers have produced taste aversions with CS–US intervals of several hours.
What is a compound stimulus? Describe the experiment that one of Pavlov’s assistants conducted with a compound stimulus on a dog, including the results of the experiment. (p. 72)
In a compound stimulus, the CS consists of two or more stimuli (e.g., a red light and a buzzer) presented simultaneously.
In one of the first studies of compound stimuli, one of Pavlov’s assistants simultaneously presented cold and tactile stimulation to a dog, followed by a few drops of mild acid in the mouth (a US for salivation). Then the experimenter tested the dog with the cold stimulus alone, the tactile stimulus alone, and the compound stimulus. The results revealed that although both the tactile stimulus and the compound stimulus were effective conditional stimuli, the cold stimulus alone was utterly ineffective.
Define overshadowing. What features of a stimulus (when presented as part of a compound stimulus) are responsible for overshadowing? (p. 72)
The phenomenon in which one part of a compound stimulus overpowers the other is known as overshadowing because, as Pavlov noted, “The effect of one [stimulus] was found very commonly to overshadow the effect of the others almost completely.”
Perhaps the chief distinguishing characteristic of an effective CS is its intensity: Strong stimuli overshadow weak ones.
The intensity of the US is also very important, with stronger stimuli producing better results, in general, than weaker ones.
How does prior experience with a CS influence the effectiveness of Pavlovian conditioning? What is latent inhibition? (p. 74)
The effects of a conditioning procedure depend partly on the individual’s previous exposure to the stimuli that will serve as CS and US. Suppose, for example, that a dog hears a bell that is sounded repeatedly but is never paired with food. If an experimenter then begins pairing the bell with food, how will the dog’s previous experience with the bell affect learning?
Research shows that the appearance of a stimulus without the US interferes with the ability of that stimulus to become a CS later (see Figure 3-6). This phenomenon is called latent inhibition. It probably occurs at least partly because prior exposure undermines the contingency between the CS and US during training.
Define blocking. Compare and contrast blocking and overshadowing. (pp. 74–75)
Suppose, for example, that a researcher conducts an experiment on Pavlovian learning in rats, first by repeatedly pairing a tone and an electric shock, then by repeatedly pairing a compound stimulus consisting of the tone and a novel stimulus (light) with the shock. What will happen if the researcher now presents the light alone? Leon Kamin (1969) performed this experiment and found that the light did not become a CS. This phenomenon, called blocking, resembles overshadowing in that one stimulus interferes with the ability of another to become a CS. In overshadowing, however, the effect is the result of differences between the stimuli in characteristics such as intensity; in blocking, the effect is due to prior experience with one part of a compound stimulus.
Describe how blocking might work for us and against us. (p. 75)
Comment: As we have emphasized, the basic procedure for establishing a neutral stimulus as a CS is to present that stimulus and quickly follow it with an unconditional stimulus (US). Overshadowing and blocking employ the basic Pavlovian conditioning procedure, but fail to establish the neutral stimulus as a CS. In overshadowing, two neutral stimuli are presented simultaneously and are followed by the US. If one of these stimuli comes to function as a CS and the other stimulus doesn’t, we would say that the first stimulus overshadowed the second. In blocking, a CS is initially established in the standard fashion (by pairing it with a US). Then, in subsequent trials, this CS is simultaneously presented with a neutral stimulus, and both stimuli are then followed by the US. If the neutral stimulus fails to come to function as a CS, we say that the previously established CS blocked the neutral stimulus from becoming a CS.
In both overshadowing and blocking, the failure of the neutral stimulus to become a CS often occurs because the organism is attending to the other stimulus, perhaps because the other stimulus is more prominent or salient.
Overshadowing and blocking probably occur to a significant degree in everyday life (though they have only been studied in laboratory settings). For example, suppose your cafeteria lunch is served on a tray. The sight of food has probably been established as a CS for salivation because it has regularly preceded food in your mouth (an US for salivation). Every day, the sight of both the food and the tray precede food in your mouth, a pairing arrangement that might establish the sight of both (either) food and the tray as conditional stimuli for salivation. However, seeing the tray alone may never act as a CS for salivation, because it is blocked by the pre-existing CS (sight of the food). Conceivably, more of your attention is directed at the food than at the tray.
Blocking would seem to be a useful phenomenon. Exposure to a stimulus that signals an important event, such as the availability of food or a danger such as a predator, helps us prepare for that event and thereby survive. But there is little additional benefit from duplicate signals; in blocking, we are merely ignoring duplicate signals.
Blocking might, however, work against us. When we eat foods that make us sick to our stomach, we tend to feel nauseated when we taste those foods again. We therefore avoid those foods, and that can help us survive. But suppose you eat a mango, a tropical fruit with a distinctive flavor, for the first time and later become slightly nauseated. Months later, you eat a bowl of fresh fruits that includes slices of mango and cranberry, a fruit that’s new to you. If you then become sick, thanks to blocking you are likely to develop an aversion to mango—even though it may have been the cranberries that made you ill.
What is sensory preconditioning? (p. 75)
Suppose two neutral stimuli, such as a bell and a light, are repeatedly presented together but are not paired with a US. Then one of these stimuli, perhaps the bell, is repeatedly paired with an unconditional stimulus so that it becomes a CS. What effect will this procedure have on the capacity of the light to become a CS? Wilfred Brogden (1939b), using dogs as subjects, paired a light and a bell for 2 seconds 20 times a day for ten days. Then, for some of the dogs, he repeatedly paired the bell with a mild shock to one of the animal’s front legs to elicit a reflex movement. Next, Brogden presented the light to see what would happen. He found that this stimulus often elicited a CR even though it had never been paired with the US. Brogden called this phenomenon sensory preconditioning. Dogs that had not been exposed to the bell–light pairing did not respond to the light in this way. In general, then, a stimulus will become a CS more rapidly if it has been paired with another stimulus that has since become a CS.
Describe the relationship between the number of pairings of the CS and US on Pavlovian conditioning. Is the relationship linear? Explain. What are the implications of this for survival of a species? (pp. 75–76)
The relationship between the number of stimulus pairings and the amount of learning is not linear: The first several pairings are more important than later ones. Thus, conditioning usually follows a decelerating curve.
From a survival standpoint, the curvilinear relationship between CS–US pairings and learning makes excellent sense. If important events reliably occur together, the sooner the individual adapts, the better. If, for example, you see a black widow spider and then receive a painful bite, it is important that you acquire a healthy fear of those spiders. People who require several CS–US pairings for learning in this kind of situation are obviously at a serious disadvantage.
What is the relationship between length of the intertrial interval and the effectiveness of Pavlovian conditioning? (p. 76)
In general, experiments comparing various intertrial intervals find that longer intervals are more effective than shorter ones. While the optimum interval between CS and US is often a second or less, the best intertrial interval may be 20 seconds or more.
How do age, temperament, and stress affect Pavlovian conditioning? (p. 77)
In eyeblink trials, learning was closely related to age; in fact, the procedure was not effective in establishing a conditional eyeblink in the oldest subjects.
Temperament can also affect conditioning. Pavlov noticed that some dogs are highly excitable, whereas others are much more sedate. He found that these differences, which may be largely due to heredity, affect the rate of learning: the more excitable dogs learned faster.
Stress also affects conditioning. Janet Taylor (1951) found that anxious students acquired conditional responses more quickly than those who were more relaxed (see Figure 3-9). Richard Servatius and colleagues (2001) also found that, in general, stress facilitated Pavlovian learning, but Michael Zorawski and his colleagues (2005) found that the effects of stress may vary with gender.
Define a Pavlovian conditioning extinction procedure. Under what conditions do we say that a CS-CR relationship has been extinguished? (p. 78)
Comment: One form of therapy based on Pavlovian extinction is called flooding. In flooding, the CS for fear is presented in intensive maximal form. For example, to treat fear of snakes using flooding (also called implosive therapy), a therapist might ask a client to imagine being in a cave, surrounded by hundreds of snakes. This method teaches the fearful individual that imagining (and eventually, actual exposure to) the feared stimulus need not produce an unpleasant US. As you can imagine, flooding therapy elicits a lot of fear all at once, so fearful people are not generally eager to try it. In this unit’s conceptual exercise, you will be asked to identify examples of flooding.
The procedure of repeatedly presenting the CS alone is called extinction. When, as a result of this, the CR no longer occurs (or occurs no more than it did prior to conditioning), we say that it has been extinguished.
