Classical Conditioning II
Module 05 Reading
CHAPTER 5
CLASSICAL CONDITIONING II: BEYOND THE BASICS
ACQUISITION EFFECTS
Cue Competition
Blocking
Overshadowing
Cue Facilitation
Potentiation
Check Your Learning: Acquisition Effects
EXTINCTION EFFECTS
Facilitated Reacquisition
Renewal of the CR
Check Your Learning: Exctinction Effects
TASTE AVERSION LEARNING
Challenges to the Traditional View of Classical Conditioning
Multiple versus Single CS-US Pairings
Optimum CS-US Interval
Cue-to-Consequence//Preparedness Effects
Long-Lasting Nature of Taste Aversion Learning
Summary Observations
Check Your Learning: Taste Aversion Learning
THEORETICAL ACCOUNTS OF CLASSICAL CONDITIONING
Pavlov’s Stimulus Substitution Theory
The Rescorla-Wagner Theory
Acquisition and Extinction in the Rescorla-Wagner Model
Overshadowing in the Rescorla-Wagner Model
The Comparator Hypothesis
Check Your Learning: Theoretical Accounts
Learning in the Real World: Phobias and the Renewal Effect
Online Resources
Key Terms and Definitions
References
Tables
Figures
A family we know once used a home ice cream maker to make a batch of ice cream from fresh peaches. They had never made peach ice cream before; in fact, no one in the family recalled having eaten peach ice cream. They looked forward to this novel treat and enjoyed eating it. However, unfortunately, there was an illness-inducing pathogen in the ice cream maker or one of the ingredients, for the entire family got sick with vomiting and diarrhea shortly after eating the ice cream. For the rest of their lives, the children never chose to eat peach ice cream.
It is quite likely that you, a friend, or a family member also can relate a similar story concerning a particular food that is on your “I will never eat that food” list. As you will see in this chapter, incidents such as these clearly show classical conditioning at work in our everyday lives.
ACQUISITION EFFECTS
Because classical conditioning enables humans and animals to adapt to their environment by anticipating and preparing for environmental events, researchers have continued their quest to understand this important form of associative learning more fully. In addition to yielding relevant data, ths research has formed the basis for several influential theories. We examine both research findings and theoretical advances in this chapter. To facilitate this presentation, we will deal with acquisition and extinction effects in separate sections, and because of its singular importance to our understanding of classical conditioning and learning in general, a separate section on conditioned taste aversions follows these two sections. We conclude the chapter with a section on theoretical advances in classical conditioning.
Classical conditioning researchers initially adopted the view that all stimuli could be conditioned and become a CS. According to their theories, it made no difference if the stimulus was visual, auditory, or tactual; pairing it with a US would automatically result in classical conditioning. Likewise, early researchers also believed that if several stimuli were simultaneously paired with a US, all of these stimuli would become CSs that were equally effective in eliciting a CR. However, as research progressed, it became clear that many of these assumptions needed revision.
Cue Competition
One of the unexpected research findings was that the to-be-conditioned stimuli actually appeared to compete with each other for the ability to become a CS and, therefore, predict the US. As a result, some stimuli became more strongly conditioned (i.e., became better predictors). This concept of cue competition refers to effects in which the ability of a stimulus to become a CS (i.e., the conditionability of that stimulus) is influenced by the presence of other stimuli. To illustrate our point, we turn to the two most widely studied cue-competition effects are blocking and overshadowing.
Blocking. Recall that, according to basic classical conditioning theory, the simple pairing of a stimulus with a US is the necessary and sufficient condition for establishing that stimulus as a CS. If that is true, then when that stimulus is paired with the US should not matter.
However, a study reported by Kamin (1969) directly questioned the validity of this assumption. His findings formed the basis of the concept of blocking, which occurs when the prior conditioning of one stimulus precludes the conditioning of a second stimulus.
In Kamin’s study, two groups of rats were the test subjects in a three-phase experiment. During Phase 1 the Experimental Group experienced several pairings of a tone and mild electric shock; the Control Group received no conditioning during this phase. During Phase 2, the Experimental Group experienced several pairings of the tone and a light followed by mild electric shock; the Control Group experienced several pairings of the light and shock. In Phase 3 both groups were tested for conditioning to the light. The experimental design appears in Table 5.1.
[[Insert Table 5.1, Experimental Design of a Blocking Experiment, about here]]
The results of this experiment showed that the Experimental Group had a significantly weaker CR to the light than did the Control Group. The weaker CR appears to be a result of blocking; conditioning of the tone as a predictive CS in Phase 1 blocked conditioning of the light in Phase 2 for the Experimental Group.
Experiments of this type indicated clearly that classical conditioning was not a simple, automatic process where any and all stimuli became associated with whatever US happened to be present. The blocking phenomenon has been replicated numerous times in both humans and animals (e.g., Giftakis & Tait, 1998; Oades, Roepcke, & Schepker, 1996; Symonds & Hall, 1997) and shows that conditioning of a stimulus during the first of two sequential phases of an experiment can impact the subsequent conditioning of another stimulus.
For example, Ilene Bernstein and her colleagues (Bernstein, 1978; Bernstein & Webster, 1980) have shown that children who ate Mapletoff ice cream (an unusual, novel flavor) prior to receiving their nausea-producing chemotherapy cancer treatment subsequently ate less of the Mapletoff ice cream than did a group of children who had not eaten the ice cream prior to receiving chemotherapy. Clearly, a conditioned taste aversion was established (see Chapter 4); the unusual flavor was conditioned to the nausea. These researchers also showed that consumption of the Mapletoff ice cream before chemotherapy decreased the children’s reluctance to eat their regular diet. It would appear that the formation of a taste aversion to the novel ice cream blocked the formation of an aversion to the normal diet and helped avert a nauseous reaction to the normal diet. We will have more to say about the intriguing phenomenon of taste-aversion learning later in this chapter.
___________________________________________________________________
Think Ahead
**** As you just saw, the blocking paradigm involves the sequential presentation of two stimuli that the experimenter is attempting to establish as CSs. What do you think the result would be if, instead of presenting the two stimuli in sequence, the experimenter presented them simultaneously (followed by a US, of course) and then tested for conditioning to each of the two stimuli? Write down some possibilities before you read further.
_________________________________________________________
Overshadowing. Research using the simultaneous presentation of two stimuli has demonstrated that under most conditions the stimuli can, and do, compete with each other to become CSs. If one stimulus is easier to condition, then that stimulus will gain more associative strength with the US (i.e., be a better predictor of the US). This phenomenon is known as overshadowing. For example, an experimenter might present a compound stimulus consisting of a loud tone and a weak light followed by food and observe stronger conditioning to the loud tone. The overshadowing effect occurs in both humans and animals (Specht, 1995).
Cue Facilitation
Even though blocking and overshadowing are well-researched and replicated phenomena that clearly support the concept of cue competition, they don’t always account for what occurs when multiple stimuli are presented for conditioning. Interestingly, another line of research has demonstrated the existence of a phenomenon known as cue facilitation.
__________________________________________________________
Think Ahead
**** Given what you have learned about cue competition, how would you expect cue facilitation to be described and defined? Write down your answer before you read further.
__________________________________________________________
You might think of cue facilitation as the opposite of cue competition. In essence, cue facilitation occurs when the pairing of two stimuli with a US results in enhanced or potentiated conditioning to one of these cues. Hence, the term potentiation is most frequently found in the research literature. This intriguing line of research originated within the context of the conditioned taste aversion paradigm, something we will explore further later in the chapter.
Potentiation. Potentiation refers to the enhancement of a CS’s ability to elicit a CR by pairing it with another stimulus during conditioning. Rusiniak, Hankins, Garcia, and Brett (1979) appear to be the initial researchers to report this phenomenon. In a series of experiments with rats, they provided either a compound stimulus composed of a weak odor and a strong, novel flavor or a single stimulus composed of the odor. Afterwards, they induced illness in the rats. The rats receiving the compound stimulus prior to illness induction exhibited a stronger odor aversion than did the rats that received only the odor-illness pairing. Thus, the presence of the taste potentiated (enhanced) conditioning to the odor.
Subsequent research replicated the potentiation effect and indicated that conditioning of other compound stimuli, in addition to those composed of an odor and a taste, can produce potentiation. For example, Davis, Best, and Grover (1988) reported that pairing a compound stimulus composed of two tastes (denatonium saccharide [a bitter-tasting chemical] and saccharin [which tastes sweet]) with illness resulted in a stronger saccharin aversion in rat subjects. Other researchers using different flavors have replicated the taste-taste potentiation effect (e.g., Bouton, Dunlap, & Swartzentruber, 1987).
A careful analysis of the potentiation effect indicates that it is the opposite of overshadowing. Thus, in situations producing potentiation, the stimuli that are conditioned do not compete for associative strength with the US. Instead, the presence of multiple cues enhancs learning.
Having established that the opposite of overshadowing was an experimentally replicable phenomenon, researchers examined the possibility that the converse of blocking might also be obtained.
_________________________________________________________
Think Ahead
****Describe what you would expect to find as the result of an experiment that produced the converse of blocking. Before you read further, write down your ideas.
_________________________________________________________
Table 5.2 shows the design of an experiment that produced the converse of blocking. Clearly this design is exactly the same as a typical blocking experiment; the only difference is that the Phase 1 conditioning to Stimulus A for the Experimental Group resulted in stronger Phase 2 conditioning to Stimulus B for that group.
[[Place Table 5.2, Experimental Design Used by Batsell and Batson (1999) to Produce the Converse of Blocking, about here]]
Using rats as test animals, Batsell and his colleagues have demonstrated and replicated this type of potentiation effect. As you can see in Table 5.2, the basic procedure used by Batsell and Batson (1999) was to condition an odor aversion in the Experimental Group in Phase 1. Then, in Phase 2, the Experimental Group received the combination of odor + taste followed by illness; whereas the Control Group received only taste followed by illness. The potentiated taste aversion shown by the Experimental Group in Phase 3 indicated that this experimental arrangement produced cue facilitation, not cue competition. Batsell, Paschall, Gleason, and Batson (2001) subsequently reported that reversing the order of presentation of the odor and taste stimuli also resulted in potentiation; in other words, pairing taste with illness in Phase 1 enhanced the odor conditioning in Phase 2 when the taste + odor compound stimulus was paired with illness.
Clearly, cue facilitation and cue competition are both robust phenomena. Undoubtedly, these and other acquisition effects will receive additional research attention in the coming years to determine more fully under what conditions they occur.
Check Your Learning: Acquisition Effects
Cue competition occurs when the conditionability of a stimulus is impacted by the presence of other stimuli.
Blocking occurs when the prior conditioning of one stimulus precludes the conditioning of a second stimulus.
Overshadowing occurs when one stimulus in a compound CS is easier to condition and, therefore, gains more associative strength with the US.
Cue Facilitation occurs when the pairing of two stimuli with a US results in enhanced or potentiated conditioning to one of these cues. This phenomenon is typically referred to as potentiation.
EXTINCTION EFFECTS
The extinction of classically conditioned responses has also received considerable research attention. As you will recall, extinction occurs following conditioning when the CS is presented without the US. The result of omitting the US is a gradual reduction in the strength of the CR. The procedure used to produce extinction and its results are quite straightforward. Understanding why the reduction in the strength of the CR occurs is another story, however. For example, the simplest theoretical explanation of extinction is that omission of the US gradually weakens the association between the CS and the US and that when the CS no longer elicits the CR, the association is eliminated. Although this account makes intuitive sense, it runs into trouble when spontaneous recovery is taken into account. As we saw in Chapter 4, the passage of time during extinction allows the CR to recover some of its lost strength. Thus, simple weakening of the CS-US association is not adequate to account for extinction. Research on facilitated reacquisition and the renewal effect has furthered our understanding of exrtinction.
Facilitated Reacquisition
Facilitated reacquisition occurs when, following extinction, the US is presented once again and the CR reappears more rapidly than during the original conditioning (Konorski & Szwejkowska, 1952). If extinction had been complete and the associative bond between the CS and US eliminated, then the reconditioning following extinction should have taken as long as the original conditioning. The fact that the CR reappeared more rapidly showed that, even though CRs might not be shown and experimenters might conclude that extinction is complete, some association between the CS and US still exists.
Up to this point we have discussed only three aspects of the classical conditioning situation: the CS, the US, and the CR. However, all classical conditioning experiments are conducted in an environment of some type. Researchers have realized that environmental cues also may have an effect on conditioned responding.
Renewal of the CR
Bouton and Bolles (1979) reported an experiment that highlighted the importance of environmental cues in the extinction of classical conditioning. Their basic procedure was to condition a fear response in a specific, distinctive environment; extinguish the CR is a second, very different, environment; and then test for the CR in the first environment. Ths sequence of events is diagrammed in Table 5.3.
[[Insert Table 5.3, Typical Experimental Design Used to Test for Renewal of the CR, about here]]
For example, a fear CR is conditioned to a light cue in Environment 1 by pairing a light CS and shock (Phase 1). Then (Phase 2) the CS is repeatedly presented in Environment 2 until it is extinguished. Environment 2 can differ from Environment 1 along any number of dimensions: for example, if Environment 1 was a box with smooth, dark walls, few olfactory cues, and a smooth floor, then Environment 2 might be a black box with rough, white walls, a strong, distinctive odor, and a metal grid floor. Testing under these conditions shows that despite extinction of the fear in Environment 2, the CR is renewed (returned) when the CS was presented in Environment 1 in Phase 3.
_______________________________________________________________
Think Ahead
**** We’ve just indicated that the CR “returns” when it is tested in Environment 1 in Phase 3. In Chapter 4 you learned that the return of the CR is a characteristic of spontaneous recovery. What makes CR Renewal different from spontaneous recovery? Give this question some thought and write your answer before you read further.
_______________________________________________________________
The difference between spontaneous recovery and CR Renewal concerns the effective variable in each situation. In spontaneous recovery the passage of time is the key variable, whereas the environments where conditioning, extinction, and testing occur are of paramount importance in CR Renewal.
Although demonstrating the effect of context of conditioned responding is relatively straightforward, explaining this phenomenon has proved much more difficult. If Bouton and Bolles (1979) had not also reported CR Renewal in which Phase 3 testing took place in a third, entirely different environment, then it would have been easy to theorize that environmental cues in Environment 1 were still associated with the CS and “reminded” the subjects of the shock. Because Bouton and Bolles demonstrated CR Renewal in a third, different environment that was unlike Environment 1, this cannot be the case. Thus, it appears likely that the CR Renewal effect will occur when the CS is presented in an environment other than the one where extinction took place.
On the other hand, Nelson (2002) noticed that the typical CR Renewal experiment (as diagrammed in Table 5.3) contained a confound. Because the post-conditioning sequence was to extinguish the CR in a second environment (Phase 2) and then test for the CR in the original or another novel environment (Phase 3), it could be either the inhibitory learning that occurred during extinction or information that was learned second that became context specific. Nelson addressed this confound by conducting an experiment in which this order was reversed: the animals received inhibitory learning first, then excitatory learning. The results indicated that the Phase 1 (inhibitory) learning generalized during Phase 3 testing in a novel environment; whereas, the Phase 2 (excitatory) did not. Thus, Nelson concluded that the information that animals learned second was more context specific. Now, the question that researchers had to deal with was why the second set of learned associations became context specific.
Bouton (1993, 1997) provided a possible answer to this question. His view of this sequence of events is that because conditioning is excitatory in one phase of the experiment and inhibitory in another phase, the meaning of the CS becomes ambiguous; sometimes the US follows the CS, sometimes it does not. Thus, the context provides a cue as to the current meaning of the CS. More specifically, when a CS becomes ambiguous a process known as occasion setting helps clarify the situation. Occasion setting occurs when a particular stimulus helps to retrieve a specific memory. The stimulus responsible for this memory retrieval is known as the occasion setter. In the case of CR Renewal, the occasion setter would be the context in which the second set of associations was learned. An occasion setter, such as the context, tells the animal the meaning of the CS that is presented; it does not directly influence responding.
Check Your Learning: Extinction Effects
Facilitated reacquisition occurs when an extinguished CR is reconditioned more rapidly than the original conditioning.
Renewal of the CR occurs when an extinguished CR returns upon testing in a different environment.
Occasion setting occurs when a particular stimulus helps retrieve a specific memory.
TASTE AVERSION LEARNING
Because the topic of taste aversion learning came up several times in our introduction to classical conditioning (Chapter 4) and in our current discussion of recent development in classical conditioning, we believe it is important to include a separate section on this topic. You will recall that the basic procedure for establishing a learned taste aversion is for consumption of a novel flavor to be followed by illness; the result is avoidance of the previously novel flavor. Thus, a food that might have become a signal for consumption becomes a signal for aversion. Because taste aversions are not established as strongly with familiar tastes, it is important that the to-be-conditioned flavor be novel.
As an example, the family we mentioned at the beginning of the chapter got sick after eating peach ice cream, which was a novel flavor for them. Had the illness happened with a common flavor like vanilla or chocolate, it is likely that they subsequently would have been willing to try, and enjoy, vanilla or chocolate ice cream despite the one experience of illness.
_______________________________________________________
Think Ahead
**** Imagine you are conducting a taste aversion experiment. Your conditioning procedure is straightforward: allow the test animals to consume a novel saccharin flavor and then induce illness after a designated time period. On the other hand, you are not exactly sure how you will test for the effects of taste aversion learning. Give this issue some thought and write down some possible tests you might conduct before you read further.
_______________________________________________________
Testing for a flavor aversion usually involves either a one-bottle or a two-bottle test. In the one-bottle test, consumption of the novel flavor (often saccharin) is compared between the taste aversion conditioned animals and a control group that has not received conditioning to this flavor (Batsell & Best, 1993). The two-bottle test, which is very useful in detecting weak aversions (Grote & Brown, 1971), asks a thirsty animal to make a choice between consuming a familiar flavor (e.g., water) and consuming a novel flavor (e.g., saccharin). Animals that have received taste aversion conditioning to the novel flavor drink significantly less of that flavor than control animals that have not received conditioning to that flavor.
We indicated in Chapter 4 that, when it was originally developed by John Garcia and his colleagues (e.g., Garcia, Ervin, & Koelling, 1966; Garcia, Kimeldorf, & Koelling, 1955; Garcia & Koelling, 1966), taste aversion learning challenged several of the then-accepted views of the nature of classical conditioning. We examine several of these challenges in the following section.
Challenges to the Traditional View of Classical Conditioning
Taste aversion learning caused investigators to reexamine the need to administer several CS-US pairings with a short interval separating the CS and US in order to establish strong conditioning.
Multiple versus Single CS-US Pairings. Whereas other types of classical conditioning, such as eyeblink and fear conditioning, require several CS-US pairings, researchers typically establish strong taste aversion conditioning with a single flavor-illness pairing (e.g., Cannon et al. 1985)
Optimum CS-US Interval. Recall that prior to the demonstration of taste aversion learning, most classical conditioning researchers believed that a CS-US interval of 0.5 sec was optimal to establish the CS-US association; extending this interval by only a few seconds usually resulted in much weaker conditioning. On the other hand, strong taste aversion conditioning can occur when the CS and US are separated by substantial periods of time. An experiment by Smith and Roll (1967) demonstrated clearly this unusual feature of taste aversion learning. These researchers conditioned a taste aversion in groups of rats under one of eight CS-US intervals that ranged from 0 US delay to 24-h US delay. Preference testing for water versus the novel saccharin flavor (a two-bottle test) took place 24 h following conditioning. All groups of animals showed strong aversions to the saccharin flavor.
Cue-to-Consequence/Preparedness Effects. Taste aversion research also demonstrated that not all neutral stimuli were equivalent in their ability to become associated with various stimuli. For example, Garcia and Koelling (1966) reported an experiment that involved conditioning a compound stimulus (flashing light + clicking sound + novel saccharin flavor) to either an electric shock (one-half of the test animals) or illness (the remaining test animals). Following conditioning, half the animals that experiences the shock US were tested for strength of conditioning by presenting the flashing light + clicking sound (a visual and auditory stimulus); the remainder of the shock-conditioned animals received presentations of the saccharin flavor. The same CS presentations were administered to the animals that received the illness US during conditioning. This experiment is diagrammed in Figure 5.1.
[[Insert Figure 5.1, Diagram of the Garcia and Koelling (1966) Experiment, about here]]
As you can see from this diagram, the animals that received the electric shock US and were tested with the flashing light + clicking sound CS had a stronger CR than did the shock-conditioned animals that were tested with the saccharin flavor CS. Conversely, the animals that experienced the illness US and were tested with the saccharin flavor CS showed stronger conditioning than did the illness-exposed animals that were tested with the flashing light + clicking sound CS.
Based on results such as these, it might be tempting to propose a general principle: tastes are associated more readily with illness than other stimuli. However, research reported by Wilcoxin, Dragoin, and Kral (1971) indicated that this principle did not apply to all conditioning episodes. These researchers presented quail with a blue-colored, sour-tasting water CS and then induced illness. Later, they gave half of the birds sour-tasting (but not blue-colored) water to drink, whereas the remaining birds were given blue-colored (but not sour-tasting) water to drink. The sour-tasting water was readily consumed, whereas the other quail refused to drink the blue-colored water.
__________________________________________________________
Think Ahead
**** Take a few moments and review the two experiments with quail that we’ve just described. What do the results of these studies tell us? Write down your answer before you read further.
__________________________________________________________
The Garcia and Koelling (1966) and Wilcoxin et al. (1971) experiments prompted two major conclusions. First, certain stimuli can form associations with certain USs more readily than they can form associations with other USs. Second, which stimuli are more easily associated with which USs appears to be species specific.
Researchers were quick to recognize the importance of these results. If animals are able to associate certain stimuli more quickly and easily with certain USs than with other USs, then it is possible that they have an innate potential to make these associations (Seligman, 1970). This innate potential is known as preparedness. Moreover, the Wilcoxin et al. (1971) data indicated that the nature of this preparedness may be species specific and evolutionarily based. In support of this conclusion these researchers noted that the gustatory (taste) and olfactory (smell) systems of rats are highly developed, whereas their visual system is not highly developed. The converse is true for quail. Thus, it makes adaptive sense for quail with their superior vision to be innately prepared to visual stimuli and for rats with their superior taste and smell to be prepared to make associations to these stimuli.
Long-Lasting Nature of Taste Aversion Learning. Another apparently unique feature of taste aversion learning is its extreme resistance to extinction. For example, Garcia, Kimeldorf, and Koelling (1955) exposed rats to radiation to condition an aversion to saccharin. Following 60 days of preference testing after one CS-US pairing, one group of test animals had not reached preference level that was comparable to that of control (nonradiated) animals. This long-lasting nature also is characteristic of human taste aversions (Logue, 1985; de Silva & Rachman, 1987).
Summary Observations
Summarizing these various lines of research, we have seen that taste aversions
are developed after only one CS-US pairing;
are developed when tastes are paired with certain stimuli, but not others;
can be enhanced or potentiated when they are conditioned to a compound CS (e.g., an odor + a taste; two tastes); and
can be extremely long-lasting and resistant to extinction in animals and humans.
Without question these results challenged the then-popular conception of the nature of classical conditioning (Garcia, 1981). Were these challenges also sufficient to convince researchers that taste aversions might represent an entirely unique form of learning? The answer would appear to be no. Several lines of research support this conclusion.
First, research has shown that selective associations can be established in both the instrumental learning paradigm (LoLordo & Droungas, 1989) and in fear conditioning (Ohman & Mineka, 2001). These results show that cue-to-consequence (or preparedness) learning is not limited just to taste aversions. Second, Bouton (2006) has indicated that one-trial learning does occur in other situations; hence, it is not unique to taste aversion learning. Bouton also indicated that if the researcher reduces or eliminates distracting stimuli, then the CS-US interval can be extended in other conditioning situations; hence, long-delay conditioning is not unique to taste aversion learning. On the other hand, the potentiation effects yielded by taste aversion research have not been mirrored by research on other types of classical conditioning. This inconsistency notwithstanding, these discrepant results may simply mean that the stimuli that compose compound CSs do not have to compete with each other on all conditioning occasions.
Clearly, taste aversion research has increased our knowledge of classical conditioning during the past several decades. Both our understanding of the nature of the conditioning process and the theoretical accounts of classical conditioning have benefitted. We turn now to these theoretical accounts.
Check Your Learning: Taste Aversion Learning
Because strong taste aversions (a) can be established with a single CS-US pairing in which the CS and US are separated by a lengthy time period and (b) are very long lasting, they challenged the traditional views of classical conditioning.
Taste aversion learning suggests that there is an innate preparedness to make certain CS-US associations and that this preparedness may be species specific.
THEORETICAL ACCOUNTS OF CLASSICAL CONDITIONING
As you will see in Chapter 12, Smith and Davis (2010) indicate that “A theory is a formal statement of the relations among the relevant variables in a particular research area” (p. 5). One of the main uses of a theory is to help organize and make sense of research data. In this section we will examine Pavlov’s early theory of classical conditioning to see how he attempted to make sense of the large amount of data he collected. Then, we will discuss more contemporary theoretical accounts.
Pavlov’s Stimulus Substitution Theory
Because he was a physiologist, Pavlov was interested in what types of changes might be taking place in the brain during conditioning. He even referred to the salivation that he studied as a “psychic secretion” that would reveal information concerning the reflexes of the brain. His theoretical speculations about such changes revolved around his conception of brain centers and the relations among these centers (Pavlov, 1927). For example, when an experimenter presented meat powder to a test animal, the meat powder activated a US center in the brain. Once activated, the US center automatically and innately activated a UR brain center, which, in turn automatically activated the neural pathways needed to make a response. This sequence of events is diagrammed in Part A of Figure 5.2.
[[Insert Figure 5.2, diagram of Pavlov’s experiment, about here]]
Pavlov assumed that there was a separate brain center for every US and every UR. However, his limited knowledge of brain physiology kept him from specifying whether a brain center consisted of one or several neurons. Given our current knowledge of the brain, it appears that these specifics were not crucial for his theory.
__________________________________________________________
Think Ahead
**** According to what we’ve already said about Pavlov’s theory, what would you expect to occur when a CS, such as a ticking metronome, was presented to a test animal? Develop an answer to this question and write it down before you read further.
__________________________________________________________
If you indicated that the ticking metronome (the CS) also activated a brain center, you are absolutely correct. The result of presenting both the US and CS is diagrammed in Par B of Figure 5.2.
Now, the only thing left to occur was for the CS center to become associated with the Response center. Unfortunately, Pavlov did not specify exactly how the CS came to elicit the response; as you can see from Part C in Figure 5.2, there are two possibilities. First, the CS center could become associated with the US center, and the US center would, in turn, activate the Response center to initiate the response. A second possibility would be for the CS center to become associated with the Response center and directly activate it. In either instance, Pavlov believed that the CS was able to substitute for the US and activate the Response center; hence, researchers have given the name “Stimulus Substitution Theory” to Pavlov’s theoretical account. Of course, Pavlov also believed that the ability of the CS to elicit a CR grew stronger as the number of conditioning trials increased.
_________________________________________________________
Think Ahead
**** Review the two possibilities for eliciting a response that we have just discussed. Consider the specific nature of the elements that are involved in each possibility. Can you think of descriptive terms for each of these modes of response elicitation? Write down some possibilities before reading further.
_________________________________________________________
The first arrangement, where the CS and US brain centers become associated, would be an S-S Association (stimulus-stimulus), whereas the association of the CS center with the Response center would be an S-R Association (stimulus-response). Although he lacked the support of research data, Pavlov (1927) appeared to favor the S-S interpretation.
Certainly, Pavlov’s theoretical interpretation of classical conditioning offered a starting point for theoreticians. However, the stimulus substitution theory was not able to account for several classical conditioning phenomena that researchers had discovered. For example, as we noted earlier, the blocking effect reported by Kamin (1969) indicated that simply presenting a stimulus and following it with a US does not always guarantee the conditioning of that stimulus. Clearly other factors are involved.
The Rescorla-Wagner Theory
The highly influential theory that Rescorla and Wagner (1972) developed is a mathematically based model that attempts to predict classically conditioned responding on a trial-by-trial basis. Although the mathematics may be a bit challenging, the logic of this model is quite straightforward.
According to this model, during classical conditioning the human participant or animal subject acquires information about the meaning of signals. For example, a rat may learn that a tone (CS) is followed by shock (US). Thus, after several CS-US pairings the rat comes to expect the delivery of shock when it enters the conditioning situation and the tone sounds.
The Rescorla-Wagner model assumes that learning occurs when there is a discrepancy between what is expected and what actually occurs. Hence, learning should occur when a rat that expected a strong shock following a tone received a mild shock. Likewise, a dog that expected that meat powder would follow the ticking sound of a metronome would be surprised when the metronome sounded and it did not receive any meat powder. Surprise is one of the key components of the Rescorla-Wagner theory. When the US is surprising, the signals for that surprising US are relevant and need to be remembered; hence, learning occurs in surprising conditions. Mathematically, the degree of surprise is expressed as the difference between the expected US and the US that is received.
Let’s see how this theory would account for the blocking effect. Recall in the typical blocking experiment that CS1 is conditioned to the US in Phase 1. Then, in Phase 2, CS1 and a second stimulus (CS2) are presented together and followed by the US. Phase 3 testing reveals that CS2 does not elicit a CR. Because the expectation of the US is confirmed during Phase 2, there are no surprising events and learning does not occur. Therefore, when CS2 is tested in Phase 3, the Rescorla-Wagner model would predict that it would not elicit a CR. If, however, CS2 were now presented by itself and followed by the US, that sequence of events would be surprising and learning would take place.
Now that you have seen how this theory can account for a research finding, such as blocking; here are several principles of the Rescorla-Wagner model that you will want to keep in mind as you read the following descriptions. Five of these principles follow logically from what we have already considered.
When the expectation of the US is the same as the actual US, no learning occurs. The CS accurately predicted the US that occurred.
When the expectation of the US is greater than the actual US, inhibitory conditioning occurs. The actual US was less than the expectation.
When the expectation of the US is less than the actual US, excitatory conditioning occurs. The actual US exceeded the expected US. In considering Principles 2 and 3, you should keep in mind that the greater the difference between the expected US and the actual US, the greater the surprise and, therefore, the greater the conditioning.
Stimuli that are more noticeable or salient will become CSs more readily than less noticeable stimuli.
In a situation where a compound stimulus is presented, the expectation will be the sum of the strengths of the individual expectations. For example, if two excitatory CSs each having an arbitrary value 6 are presented, then the strength of the expected US would be 12. Likewise, if a compound CS consisting of an excitatory CS with a value of 7 and an inhibitory CS with a value of 5 is presented, the resultant expectation would be excitatory and have a value of 2.
These mathematically derived principles enabled the Rescorla-Wagner model to account for additional classical conditioning phenomena. Following are two examples.
Acquisition and Extinction in the Rescorla-Wagner Model. Because the actual US exceeds the expected US during acquisition, the Rescorla-Wagner theory would predict an increase in excitatory conditioning until the expected US and the actual US coincide. At that point conditioning would be complete. The converse would hold true for extinction. Because the value of the expected US is greater than the actual US, inhibitory conditioning would occur until the expected US and actual US are equivalent.
Overshadowing in the Rescorla-Wagner Model. Overshadowing, as we saw earlier in this chapter, occurs when a compound stimulus consisting of a strong stimulus and a weak stimulus is conditioned. Later, when the component stimuli are presented individually to test for conditioning, the Rescorla-Wagner model would predict that the strong, noticeable CS was conditioned more strongly and would elicit a stronger CR. This is exactly what happens.
You can view the Rescorla-Wagner model as a theory that focuses on what the subject knows about the US, those conditions that can cause a change in this knowledge, and how those changes are predicted to be translated into responding. On the other hand, other theories have stressed problems with response performance.
The Comparator Hypothesis
One of the more influential of the theories that stress problems with response performance is the comparator hypothesis (Miller & Matzel, 1988; Matzel, Brown, & Miller, 1987), which states that the strength of conditioning of the CS to the US is compared to the strength of conditioning of another stimulus and the US. Because a basic premise of the comparator hypothesis is that learning occurs when two or more stimuli are contiguous, it definitely belongs in the S-S category. Keep in mind that contiguity simply means being close in time or space. Keeping this basic assumption in mind, the comparator hypothesis is interested in the three associations that are formed during conditioning.
________________________________________________________
Think Ahead
**** Now is a good time to put on your thinking cap. What are these three associations that are formed during conditioning? Write down your answer before you read further.
________________________________________________________
Keep in mind that in the conditioning situation, associations are formed between:
The CS and US
The CS and the context
The context and the US
Now, let’s consider what happens when we test for a CR. In these and other examples of the comparator hypothesis, stimuli, other than the CS and US, are known as comparator stimuli. When only the CS is presented during testing, it will elicit a representation of the US and the context because it was paired with them during conditioning. In turn, the memory of the context also will elicit a memory of the US. However, the memory of the US elicited by the CS is direct; whereas, the memory of the US elicited by the representation of the context is indirect.
When the associations between the CS and comparator stimuli and between the comparator stimuli and the US are strong, the theory predicts that the animal makes a comparison between the US representation elicited directly by the CS and the US representation elicited indirectly by the context. Further, the theory assumes that strong conditioning (i.e., strong CRs) occurs when the CS is the best predictor of the US (i.e., the direct representation is a better predictor than the indirect representation). Why does the theory make this assumption?
Because the CS is presented only for a brief period of time just before the US presentation, the chance of the CS losing its association with the US is minimized. (Don’t forget that the comparator theory assumes that contiguity is all that is required for an association to be formed.) On the other hand, because the test animal remains in the conditioning context without the US, this comparator stimulus has the opportunity to form a context-No US association. Thus, comparator theory predicts that the representation of the US that is elicited by the context will be weaker than the representation elicited by the CS. When this indirect, context-US association is weak, the comparator theory indicates that it will not elicit a US representation. Hence, the CS is a better predictor of the US and should elicit a strong CR.
Yin, Barnet, and Miller (1994) put this interesting theory to a direct experimental test. They administered classical fear conditioning to two groups of rats. Even though both groups received the same number of CS-US pairings, one group received their trials in a massed condition (i.e., very little time separated each CS-US exposure). The CS-US presentations for the second group were spaced (i.e., a time period elapsed between each trial). The comparator hypothesis would make rather straightforward predictions concerning the CRs shown by these two groups; can you identify them?
First, both groups should form equivalent and strong CS-US associations because these two stimuli occur in the same manner for all animals. Likewise, the CS-context association also should be the same for both groups because all animals experience these stimuli in the same manner. However, because time elapses between CS-US presentations for the spaced-trials group, these animals will experience the context without the US and form context-No US associations. Because the massed-trials animals do not form CS-No US associations, they should have strong context-US associations and the context also will be a good predictor of the US. Thus, the comparator theory would predict that the spaced-trials animals would have stronger CRs than the massed-trials animals because the CS is a better predictor of the US than the context. The data reported by Yin et al. (1994) supported this prediction.
________________________________________________________
Think Ahead
**** Do the Yin et al. (1994) results confirm predictions made by the Rescorla-Wager model, or are these data troublesome to that theory? Write down your answer and justification before you read further.
________________________________________________________
Because the CS-US associations are equivalent for both groups, the Rescorla-Wagner model would not predict a difference in CRs for the spaced-trials and massed-trials animals. Thus, at least in this one situation, the comparator hypothesis appears to have an advantage.
Yin et al. (1994) reported a second phase in their experiment that also yielded data that were difficult for the Rescorla-Wagner model to explain. During this phase both the space- and massed-trials animals received placements in the context without the US. Thus, the context-US association was extinguished for the massed-trials group. Hence, both groups now had equivalent context-No US associations. According to the comparator hypothesis, they should show comparable, strong CRs when the CS was presented. (The Rescorla-Wagner model would not be relevant here, as it does not address this manipulation.) The results confirmed the prediction of the comparator hypothesis.
In addition to predicting unique classical conditioning results, the comparator hypothesis also can account for the blocking effect. (Now is a good time to review the basic design of a blocking experiment; refer back to Table 5.1.) The comparator account of blocking focuses on the association that the blocking group forms between the two CSs in Phase 2. During Phase 3 when the blocking animals are tested for conditioned responding to CS2 (the second CS that was conditioned during Phase 2), CS2 elicits a strong memory of both the US and CS1 (the stimulus that was conditioned in Phase 1). In turn, CS1 (the comparator stimulus) also elicits a strong memory of the US. Thus, because the comparator stimulus elicits a strong memory of the US, CS2 is not the best predictor of the US and the CR elicited by this stimulus is weak—this is the basic blocking effect.
The comparator hypothesis also would predict that weakening the association between CS1 and CS2 by extinguishing CS1 would result in a weakening of the US memory elicited by CS1 (the comparator stimulus) during CR testing to CS2. Blaisdell, Gunther, and Miller (1999) performed this experiment and reported strong CRs to CS2 following CS1 extinction. Thus, contrary to the Rescorla-Wagner model, it appears that animals do learn about CS2 during phase 2 of a blocking experiment.
Without question, contemporary research and theories have extended our knowledge of classical conditioning and its central role in adaptation to the environment. Classical conditioning certainly is vastly more complex than the early researchers believed. Continued research will help reveal the remaining complexities.
Check Your Learning: Theoretical Accounts of Classical Conditioning
Pavlov’s stimulus substitution theory of classical conditioning posited the existence of brain centers for the CS, US, and UR and stressed the associations among these centers.
The Rescorla-Wagner model stresses the importance of surprising events for the occurrence of classical conditioning. This theory is able to account for such phenomena as acquisition, extinction, blocking, and overshadowing.
The comparator hypothesis assumes that contiguity is the basis of learning and that the associations among the CS, US, and context are important in predicting responding.
Learning in the Real World: Phobias and the Renewal Effect
In your introductory psychology class you probably learned that “a phobia is an intense, excessive fear of an activity, object, or situation. The fear in a phobia is out of proportion to the real danger, and it is difficult to overcome” (Davis & Palladino, 2007, p. 528). Certainly, classical conditioning can, and likely does, play an important role in the development of phobias. For example, imagine that once, as a child, you were playing in a junkyard and accidentally got shut inside of an abandoned refrigerator for a few minutes before a playmate found you and let you out. The CS of being shut inside the refrigerator would have resulted in a lack of oxygen (US) which quite likely led to intense fear (UR). Because of this experience, it would not be unusual for you to have an intense and irrational fear and avoidance of closed spaces (claustrophobia) for years to come.
Psychologists were quick to realize that if phobias were established through classical conditioning, then it should be possible to use classical conditioning procedures to eliminate them. Theoretically, repeatedly presenting the CS without the US should extinguish the conditioned fear response. Researchers and clinicians have developed two basic procedures to achieve this goal.
In the first procedure, known as flooding (Baum, 1970), the patient is directly exposed to the CS that elicits the greatest amount of fear. Although it attacks the phobic response in the most direct manner possible, flooding does produce an intense, and potentially harmful, fear reaction. For example, in flooding therapy for claustrophobia, the patient might give permission for the therapist to shut him or her inside a small, confining closet, resembling the experience of being shut in the refrigerator. Obviously, this experience would produce a great deal of fear. However, the patient would not experience a lack of oxygen (the US). When the patient exited the closet and felt relief (i.e., when the fear aroused by the CS subsided), extinction would proceed and the phobia would dissipate.
In the second procedure, systematic desensitization (Wolpe, 1969), the patient and clinician jointly develop a hierarchy of stimuli that cause the patient to feel anxiety and fear. Then, beginning with the least fear-producing stimulus, each of these cues is extinguished until the patient is able to confront the most fear-producing cue without experiencing fear or anxiety (Mystkowski, Craske, & Echiverri, 2002). For example, the patient might begin by agreeing to be shut inside of a fairly large room (e.g., 20 by 20 feet) for 10 minutes. Once the patient is able to remain in the room for 10 minutes without feeling fear or anxiety, he or she would then try being shut in progressively smaller rooms and spaces, down to the size of a closet. The key in desensitization is that only when the patient is free of anxiety and fear in one situation does the therapy progress to a stimulus more closely resembling the original CS.
Although both of these procedures have been successful in dealing with phobias, their success is far from complete. Phobias frequently reappear and have proven to be extremely difficult to extinguish.
One factor that hinders the extinction of a phobia is spontaneous recovery, the phenomenon in which a CR that was thought to be extinguished reappears (see Chapter 4) . Even though the phobia may appear to be extinguished when a patient leaves the clinician’s office, the passage of time allows it to spontaneously recover some strength. Hence, full extinction of a phobia may require a great many sessions.
A second problem in eliminating phobias concerns where the extinction experiences take place; most likely, the patient will experience them in the clinician’s office. Now, what does the renewal effect suggest will happen under these conditions? Recall that the CR renewal effect would predict that if extinction is conducted in a context other than the original conditioning context, the CR will reappear when the subject again encounters the original context. Thus, if you have a spider phobia (arachnophobia) because you were bitten by a spider in your backyard when you were a child, then, even though your fear was extinguished in a clinical setting, you likely will have a fear reaction the next time you see a spider someplace other than where you received treatment (Mystkowski, Craske, & Echiverri, 2002).
__________________________________________________________
Think Ahead
**** What are some strategies that clinicians might use to deal with these renewal effects? Stop and write down some ideas before you continue reading.
__________________________________________________________
One possible treatment strategy is to conduct the extinction procedures in the setting where the patient is most likely to encounter the feared CS in the future (Denniston, 2008). Thus, the clinician maximizes the possibility that the feared CS will be encountered. For example, instead of extinguishing the fear of spiders in a laboratory setting, the extinction procedures might be conducted in the patient’s apartment or house. A second procedure is to extinguish the fear-producing CS in multiple contexts with the assumption that these extinction effects will generalize to other contexts as well (Gunther, Denniston, & Miller, 1998). Both of these procedures have been successful in eliminating phobias.
This completes our two-chapter examination of classical conditioning. In the next chapter we look at another basic form of learning: operant conditioning.
Online Resources
This brief article describes an easy to conduct project that clearly demonstrates the development of a conditioned taste aversion.
A fascinating article that investigates the possibility that rats can acquire a conditioned taste aversion by observing demonstrator rats that consumed a novel diet and subsequently became ill.
http://www.sociallearning.info/home/…/comp%20psych%2097(4),%20358-363.pdf
Good, expanded review of theories of classical conditioning. The section on the Rescorla-Wagner model and the blocking effect is excellent.
http://www.mnstate.edu/malonech/Psy342/Notes/CC%20Theoretical%20Ch.3.htm
Presents a complete account of the Rescorla-Wagner Model, including the mathematics that characterize this theoretical statement.
http://users.ipfw.edu/abbott/314/Rescorla2.htm
An excellent and comprehensive glossary of terms associated with the psychology of learning.
http://www.sinauer.com/bouton/glossary.html#C
The full-file pdf presents an interesting overview of the comparator hypothesis
Key Terms and Definitions
cue competition
refers to effects in which the conditionability of a stimulus is influenced by the presence of other stimuli
blocking
occurs when the prior conditioning of one stimulus precludes the conditioning of a second stimulus.
overshadowing
occurs when one stimulus in a compound CS is easier to condition and, therefore, gains more associative strength with the US.
cue facilitation/potentiation
occurs when the pairing of two stimuli with a US results in enhanced conditioning to one of these cues.
facilitated reacquisition
occurs when an extinguished CR is reconditioned more rapidly than the original conditioning.
occasion setting
occurs when a particular stimulus, the occasion setter, helps retrieve a specific memory.
preparedness
Innate potential to associate certain stimuli more easily and quickly with certain USs.
Rescorla-Wagner model
The Rescorla-Wagner model is a theory of classical conditioning in which the strength of conditioning depends on the surprisingness of the US (i.e., when there is a discrepancy between what is expected and what actually occurs).
comparator hypothesis
This theory of classical conditioning states that the strength of the CR depends on a comparison of the strength of the CS’s association with the US compared to the strength of the association of another stimulus with the US.
flooding
technique used to treat phobias by presenting the patient with a highly feared cue that is not taken away until the fear subsides
systematic desensitization
A behavioral technique based on classical conditioning, that is used to treat phobias; the technique usually combines training in relaxation with exposure to imagined scenes related to the phobia
spontaneous recovery
Reappearance of a CR that was thought to be extinguished.
References
Batsell, W. R., Jr., & Batson, J. D. (1999). Augmentation of taste conditioning by a preconditioned odor, Journal of Experimental Psychology: Animal Behavior, 25, 374-388
Batsell, W. R., Jr., & Best, M. R. (1993). One bottle too many? Method of testing determines the detection of overshadowing and retention of taste aversions. Animal Learning & Behavior, 21, 154-158.
Batsell, W. R., Jr., Paschall, G. Y., Gleason, D. I., & Batson, J. D. (2001). Taste preconditioning augments odor-aversion learning. Journal of Experimental Psychology: Animal Behavior Processes, 27, 30-47.
Baum, M. (1970). Extinction of avoidance responding through response prevention (flooding). Psychological Bulletin, 74, 276-284.
Bernstein, I. L. (1978). Learned taste aversions in children receiving chemotherapy. Science, 200, 1302-1303.
Bernstein, I. L., & Webster, M. M. (1980). Learned taste aversions in humans. Physiology and Behavior, 25, 363-366.
Blaisdell, A. P., Gunther, L. M., & Miller, R. R. (1999). Recovery from blocking through deflation of the block stimulus. Animal Learning & Behavior, 27, 63-76.
Bouton, M. E. (1993). Context, time, and memory retrieval in the interference paradigms of Pavlovian learning. Psychological Bulletin, 114, 80-99.
Bouton, M. E. (1997). Signals for whether versus when an event will occur. In M. E. Bouton & M. S. Fanselow (Eds.), Learning, motivation, and cognition: The functional behaviorism of Robert C. Bolles (pp. 385-409). Washington, DC: American Psychological Association.
Bouton, M. E. (2006). Learning and behavior: A contemporary synthesis. Sunderland, MA: Sinauer Associates.
Bouton, M. E., & Bolles, R. C. (1979). Contextual control of the extinction of conditioned fear. Learning and Motivation, 10, 445-466.
Bouton, M. E., Dunlap, C. M., & Swartzentruber, D. (1987). Potentiation of taste by another taste during compound aversion conditioning. Animal Learning & Behavior, 15, 433-438.
Cannon, D. S., Best, M. R., Batson, J. D., Brown, E. R., Rubenstein, J. A., & Carrell, L. A. (1985). Interfering with taste aversion learning in rats: The role of associative interference. Appetite, pp. 1-19.
Davis, S. F., Best, M. R., & Grover, C. A. (1988). Toxicosis-mediated potentiation in a taste/taste compound: Evidence for within-compound associations. Learning and Motivation, 19, 183-205.
Davis, S. F., & Palladino, J. J. (2007). Psychology (5th ed.). Upper Saddle River, NJ: Prentice Hall.
Denniston, J. C. (2008). Recent trends in classical conditioning. In S. F. Davis & W. Buskist (Eds.), 21st Century psychology: A reference handbook: Volume 1 (pp. 310-319). Los Angeles: Sage Publications.
Garcia, J. (1981). Tilting at the paper mills of academe. American Psychologist, 36, 149-158.
Garcia, J., Kimeldorf, D. J., & Koelling, R. A. (1955). A conditioned aversion towards saccharin resulting from exposure to gamma radiation. Science, 122, 157-158.
Garcia, J., & Koelling, R. A. (1966). Relation of cue to consequence in avoidance learning. Psychonomic Science, 4, 123-124.
Giftakis, J., & Tait, R. W. (1998). Blocking of the rabbit’s classically conditioned nictating membrane response: Effects of modifications of context associative strength. Learning and Motivation, 29, 23-48.
Grote, F. W., & Brown, R. T. (1971). Conditioned taste aversions: Two-stimulus tests are more sensitive than one-stimulus tests. Behavior Research Methods & Instrumentation, 3, 311-312.
Gunther, L. M., Denniston, J. C., & Miller, R. R. (1998). Conducting exposure treatment in multiple contexts can prevent relapse. Behavior Research and Therapy, 36, 75-91.
Kamin, L.J. (1969). Predictability, surprise, attention, and conditioning. In B. A. Campbell & R. M. Church (Eds.), Punishment and aversive behavior (pp. 279-296). New York: Appleton-Century-Crofts.
Konorski, J., & Szwejkowska, G. (1952). Chronic extinction and restoration of conditioned reflexes. III. Defensive motor reflexes. Acta Biologiae Experimentalis, 16, 91-94.
LoLordo, V. M. & Droungas, A. (1989). Selective associations and adaptive specializations: Taste aversions and phobias. In S. B. Klein & R. Mowrer (Eds.), Contemporary learning theories: Instrumental conditioning theory and the impact of biological constraints on learning (pp. 145-179). Hillsdale, NJ: Erlbaum.
Matzel, L. D., Brown, A. M., & Miller, R. R. (1987). Associative effects of US preexposure: Modulation of conditioned responding by an excitatory training context. Journal of Experimental Psychology: Animal Behavior Processes, 13, 65-72.
Miller, R. R., & Matzel, L. D. (1988). The comparator hypothesis: A response rule for the expression of associations. In G. H. Bower (Ed.), The psychology of learning and motivation (Vol. 22, pp. 51-92). San Diego: Academic Press.
Mystkowski, J. L., Craske, M. G., & Echiverri, A. M. (2002). Treatment context and return of fear in spider phobia. Behavior Therapy, 33, 399-416.
Nelson, J. B. (2002). Context specificity of excitation and inhibition in ambiguous stimuli. Learning and Motivation, 33, 284-310.
Oades, R. D., Roepcke, B., & Schepker, R. (1996). A test of conditioned blocking and its development in childhood and adolescence: Relationship to personality and monoamine metabolism. De4velopmental Neuropsychology, 12, 207-230.
Ohman, A., & Mineka, S. (2001). Fears, phobias, and preparedness: Toward an evolved module of fear and fear conditioning. Psychological Review, 108, 483-522.
Rescorla, R. A., & Wagner, A. R. (1972). A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F. Prokasy (Eds.), Classical conditioning. II: Current research and theory (pp. 64-99). New York: Appleton-Century-Crofts.
Rusiniak, K. W., Hankins, W. G., Garcia, J., & Brett, L. P. (1979). Flavor-illness aversions: Potentiation of odor by taste in rats. Behavioral & Neural Biology, 25, 1-17.
Seligman, M. E. P. (1970). On the generality of the laws of learning. Psychological Review, 77, 406-418.
Smith, J. C., & Roll, D. L. (1967). Trace conditioning with X-rays as an aversive stimulus. Psychonomic Science, 9, 11-12.
Specht, M. L. (1995). Overshadowing in landmark learning: Touch-screen studies with pigeons and humans. Journal of Experimental Psychology: Animal Behavior Processes, 21, 166-181.
Symonds, M., & Hall, G. (1997). Contextual conditioning with lithium-induced nausea as the US: Evidence from a blocking procedure. Learning and Motivation, 28,200-215.
Wilcoxin, H. C., Dragoin, W. B., & Kral, P. A. (1971).Illness-induced aversions in rat and quail: Relative salience of visual and gustatory cues. Science, 171, 826-828.
Wolpe, J. (1969). The practice of behavior therapy. New York: Pergamon Press.
Yin, H., Barnet, R. C., & Miller, R. R. (1994). Trial spacing and trial distribution effects in Pavlovian conditioning: Contributions of a comparator mechanism. Journal of Experimental Psychology: Animal Behavior Processes, 20, 123-134.
Tables
Table 5.1 Experimental Design of a Blocking Experiment
|
Group |
Phase 1 |
Phase 2 |
Phase 3 |
|
Experimental |
Tone shock |
Tone + light shock |
Test for conditioning to light |
|
Control |
No conditioning |
Light shock |
Test for conditioning to light |
Table 5.2 Experimental Design Used by Batsell and Batson (1999) to Produce the Converse of Blocking
|
Group |
Phase 1 |
Phase 2 |
Phase 3 |
|
Experimental |
Odor (A) illness |
Odor (A) + taste (B) illness |
Test for conditioning to taste (B) |
|
Control |
No conditioning |
Taste illness |
Test for conditioning to taste (B) |
Table 5.3 Typical Experimental Design Used to Test for Renewal of the CR
|
Phase 1 |
Phase 2 |
Phase 3 |
|
CR conditioned in Environment 1 |
CR extinguished in Environment 2 |
Test for CR in Environment 1 |
Figures
Figure 5.1 Diagram of the Garcia and Koelling (1966) Experiment [to be rendered]
ConditioningTesting
Flashing light
+ Strong CRClicking sound
CS (flashing light+
clicking light + Electric Shock US
novel saccharin Saccharin flavor Weak CR
Flashing light
+ Weak CRClicking sound
CS (flashing light+
clicking light + Illness US
novel saccharin Saccharin flavor Strong CR
Figure 5.2 [need a scan or copy of the art]