Classical Conditioning Research Paper

This sample Classical Conditioning Research Paper is published for educational and informational purposes only. Free research papers are not written by our writers, they are contributed by users, so we are not responsible for the content of this free sample paper. If you want to buy a high quality research paper on any topic at affordable price please use custom research paper writing services.

If you touch a doorknob and receive an electric shock, you will likely hesitate to touch the doorknob again. If you eat an exotic food and later feel sick to your stomach, you will likely avoid consuming that food in the future. You use your previous experience with the world to determine your future behavior. This capacity is partially due to the process of classical conditioning.

The Discovery Of Classical Conditioning

Classical conditioning was first extensively studied by Ivan Pavlov (1927) in the early 20th century. Pavlov was a Russian physiologist interested in the processes of digestion, specifically the production of saliva and gastric juices that result from tasting food. His subjects (dogs) were restrained and meat powder was placed on their tongue; the saliva and gastric juices that resulted from their tasting the food were then collected and measured using special devices. Salivation upon tasting food is known as a reflex because salivation is involuntarily elicited by the experience of food. Reflexes were thought to be innate and impossible to change with experience. However, Pavlov observed that the sight of an experimenter and the sounds of equipment calibration were enough to make the dogs salivate. That is, events that preceded the delivery of the meat powder were also sufficient to elicit the salivation reflex. Pavlov and his students were amazed by this discovery. Their dogs were able to anticipate what would occur in the near future! To make sure their observations were real, they designed an experiment in which the sound of a metronome preceded the delivery of meat powder to the dogs’ tongue. After many repetitions of these metronome-meat powder pairings, dogs were presented with the sounds of the metronome but no meat powder was delivered to their tongue. Because the dogs salivated to the sound of the metronome, Pavlov suggested that salivation, a reflexive response, could be produced by two different stimuli: those that produced salivation without prior experience (food), and those that subjects experienced as predicting the delivery of food (metronome).

The Elements Of Classical Conditioning: US, UR, CS, AND CR

When we talk about classical conditioning, we talk about stimuli producing responses. (Note that stimuli is the plural for stimulus.) A stimulus is an event that subjects can perceive through their senses. Thus, lights, sounds, vibrations, odors, tastes, temperature, pain, and internal sensations (e.g., stomach rumbling) can all be considered stimuli. Responses are reactions to stimuli that are usually described in terms of behavior. Thus, salivation, shivering, jumping, walking, and other behaviors are responses.

Figure 33.1  Pavlov’s basic procedure.

Classical conditioning occurs when two stimuli are paired with each other. Usually, one of those stimuli produces a response innately (i.e., without experience). Pavlov called these stimuli unconditioned stimuli (USs) because the response they elicit is not conditional on things other than the US occurring. The response produced by a US is known as an unconditioned response (UR), and it usually entails a reflex elicited by the US (e.g., salivation, muscle flexion, etc.). In Pavlov’s experiment with dogs, the stimulus that produced the salivation response unconditionally was meat powder. Thus, meat powder is a US that produces a salivation UR. In that experiment, the sound of a metronome, a neutral stimulus (NS), which did not elicit a response, preceded the presentation of meat powder. However, with repeated metronome-meat powder pairings, the metronome became a conditioned stimulus (CS), which produced a conditioned response (CR) of salivation. The salivation produced by the CS is known as conditioned because its occurrence is conditional on the CS and US having been previously paired; that is, because it results from the process of conditioning.

Laboratory Methods Used To Study Classical Conditioning

Conditioned Emotional Response (CER)

When rodents (e.g., rats and mice) anticipate danger (e.g., an approaching predator), they produce a very specific behavior: they freeze. Freezing involves becoming very still to avoid detection by predators. Estes and Skinner (1941) developed the conditioned emotional response (CER) procedure to take advantage of this tendency to freeze in anticipation of danger. In a CER study, subjects are first trained to perform a behavior such as pressing a lever to receive food reward. Once this behavior is well established, the CS-US pairings begin. The nature of the CS may vary (lights, tones, etc.), but the US is always a stimulus that triggers fear reactions, commonly a mild electric shock (just strong enough to startle the subject without producing pain). Because the CS signals the occurrence of the US, subjects come to freeze when presented with the CS. Freezing is incompatible with performing behaviors such as lever pressing; thus, disruption of this behavior by freezing can be used as a measure of conditioned fear. Because conditioned fear suppresses the occurrence of the behavior, the measure is known as conditioned suppression. Suppression scores are sometimes confusing because less behavior indicates more learning about the CS-US relation. Keep in mind that in the CER procedure we do not measure the amount of behavior, but rather the suppression of that behavior. Thus, more learning would be indicated by more suppression (less behavior) and less learning would be indicated by less suppression (more behavior).

Sign Tracking

All animals tend to approach and make contact with stimuli associated to food (they track the food signs). Birds have a stereotypical tendency to peck at stimuli that signal food. In the sign-tracking preparation (Hearst, 1975), researchers repeatedly present pigeons with a CS (e.g., a lighted button) that signals delivery of a food US (grain). At first, pigeons eat the grain and ignore the CS. However, with repeated pairings, they begin to attend to the CS, and eventually come to peck at it as soon as it is presented. Thus, the researcher can record the number of pecks at the CS to measure learning of the CS-US relation. The stronger the CS-US relation, the more they will expect the US to follow the CS, and the more they will peck at the CS.

Conditioned Taste Aversion (CTA)

Most (if not all) animals tend to avoid foods that made them ill in the past (see Chapter 35, Taste-Aversion Learning). In the conditioned taste aversion (CTA) preparation, rats are presented with a novel flavor CS (e.g., sugary water) and then they are made ill to their stomachs by either injecting them with a drug or exposing them to an illness-inducing US (e.g., radiation). As a result of these CS-US pairings, subjects come to anticipate becoming ill after consuming the CS and avoid consuming it. Experimenters measure either total consumption of the CS (more learning about the CS-US relation results in less consumption of the CS) or preference for the CS over the other flavor (more learning about the CS-US relation results in higher preference for the other flavor). Food preferences develop through a similar process, but in this case the CS is paired with an appetitive US and consumption of the flavor CS increases (see Sclafani, 1997).

Human Conditioning

Diverse methods have been used for studying conditioning with humans, ranging from delivering mild electric shock to participants’ fingertips and measuring finger flexion, to use of video games that allow experimenters to observe online records of participants’ behaviors. The tasks are very diverse, but they all present participants with pairings of a CS and a US and require subjects to provide a measurable response.

CSs or USs? A Revised Definition

Is food a CS or a US? In the sign-tracking preparation, food is a US that, when paired with a visual CS, elicits a CR of pecking. However, in the CTA preparation, food is a CS that, when paired with an illness-inducing US, produces avoidance of a flavor. The terms CS and US are not absolute; they are relative to the role that the stimulus plays in the situation. Food is a US in the sign-tracking preparation because it innately elicits a pecking UR. In contrast, food is a CS in the CTA preparation because avoidance is not elicited by the food CS without learning. Thus, a stimulus should not be labeled “CS” or “US.” These labels depend on the preparation and the responses being measured (e.g., Gunther, Miller, & Matute, 1995).

Do All CRS Mimic the URs?

In the sign-tracking preparation, the CR (pecking at the CS) closely resembles the UR (pecking at the food US). However, this is not always the case. In the CER procedure, the UR to shock is an increased level of activity (think about your own reactions to receiving an electrical shock), but the conditioned response is a decreased level of activity (freezing). Thus, CRs and URs are sometimes identical, but they can also be quite different from each other.

Is The CR Elicited Only By The CS?

Sometimes, stimuli other than the CS can produce the CR. This effect is known as stimulus generalization and it often occurs when the stimulus being tested and the CS are similar (Pavlov, 1927). For example, a pigeon trained to peck at a red circle may also peck at a highly similar orange circle, thus generalizing the CR. The opposite process is also observed: the same pigeon would not peck at a blue circle because the similarity between red and blue is low; that is, the pigeon would exhibit stimulus discrimination.

Acquisition Of Conditioned Responses

The process of developing a CR as a result of CS-US pairings is known as acquisition. Acquisition can be favored and hampered by several manipulations. First I review the conditions that determine the strength of the acquired CR, and then I describe manipulations that diminish or prevent the development of a CR.

Number and Distribution of Cs-US Pairings

In general terms, the more times the CS and US are paired, the stronger the CR that is observed. But not all pairings are equal. Most of the behavior change observed as a result of conditioning (i.e., acquisition) occurs during the first few trials. With each passing trial, the change in behavior is less and less. Plotted graphically, we would see a negatively accelerated curve, which means that the gradient of the curve is steeper during the first few trials, becoming less steep as training progresses, and finally becoming almost flat at a point known as the asymptote of learning. Asymptotic behavior represents the maximum strength of CR possible with that particular conditioning preparation. Figure 33.2 presents a hypothetical acquisition curve.

The steepness of the acquisition curve and the level of the asymptote are affected by the salience (i.e., perceived intensity) of the CS and US: More salient stimuli result in faster learning (steeper curve) and more CR (higher asymptote; see Kamin, 1965). Thus, you will learn faster to fear a loud siren signaling a dangerous fire than a dull tapping sound signaling an uncomfortable temperature. Importantly, salience is a perceived intensity, meaning that some CSs and USs may be more or less salient depending on the subject’s particular state (e.g., food is more salient to a hungry subject than to a satiated one).

Each CS-US pairing is known as a trial, and the interval between trials where there are no CS or US presentations is known as the intertrial interval. In the short run, CRs are stronger with shorter intertrial intervals (this arrangement is known as “massed” trials). However, these CRs are weak and tend to decrease as time elapses after the last CS-US trial. To observe CRs that will stand the passage of time, the CS-US pairings must be given with long intertrial intervals (“spaced” trials). This is why your professors recommend that you study every day and review the material over and over again rather than cram the night before an exam: Cramming may help you pass an exam the following day, but the material will be lost by the time finals roll in.

Contiguity

Imagine that you open a door by turning a doorknob and 10 seconds later you feel an electric shock in your hand. Imagine now that touching the doorknob is immediately followed by receiving an electric shock. In which of these two situations would you be more likely to avoid touching doorknobs in the future? Which situation makes you more certain that the doorknob signaled the shock? These two situations have the same CS (doorknob) and US (static electricity shock) pairings, but the time elapsed between CS presentation and US delivery is not the same. That is, these two situations vary in the degree of contiguity between the CS and US. Conditioning appears to be stronger the greater the degree of CS-US contiguity: As contiguity degrades, it appears more difficult for subjects to form CS-US associations (Rescorla & Cunningham, 1979).

The most common CS-US arrangement is the one in which the CS precedes the US by a short time; the US either occurs immediately following termination of the CS or at the time of CS termination. This is known as delayed conditioning because the delivery of the US is delayed until the end of the CS. CRs resulting from delayed conditioning tend to be very robust, but the strength of these CRs decreases as the interval between CS termination and US delivery is increased. At this increased interval, we talk about trace conditioning because the US presentation occurs during a memory trace of the CS. As the CS termination-US delivery interval grows longer, conditioning becomes less robust. If you were to see a bee standing on your arm and immediately feel a painful sting (a delayed CS [bee]—US [sting] pairing), you would be more likely to attribute the painful sting to the bee and fear bees in the future than if you see a bee standing on your arm and feel a painful sting several seconds later (a trace CS-US pairing).

Contiguity does not imply that the CS precedes the US. Indeed, in some situations the US may occur before the CS. Because this is a reversal of the typical conditioning situation, US-CS pairings are known as backward conditioning. Continuing with the previous example, if you were to feel a painful sting and then saw a bee standing on your arm, you would be subject to backward conditioning. Backward conditioning sometimes results in little CR; indeed, subjects may view the CS as a signal that the US is already over.

But maximal contiguity does not necessarily mean maximal responding. The greatest possible CS-US contiguity is provided by situations in which the CS and US are presented at the same time, something known as simultaneous conditioning. This type of conditioning usually results in little CR when measures such as freezing (which require subjects to prepare for a US that will soon occur) are used: if the US is already present, producing an anticipatory response may not be advantageous to subjects (Matzel, Held, & Miller, 1988).

Figure 33.3   Common classical conditioning procedures.

NOTE: The arrow represents time elapsing. The width of the rectangles represents stimulus duration. a. Delayed conditioning: US delivery is delayed until CS termination. b. Trace conditioning: There is a short gap between CS termination and US delivery. c. Simultaneous conditioning: The CS and US occur at the same time. d. Backward conditioning: The US occurs before the CS (a reversal of the usual CS—>US arrangement). The four procedures are presented in the usual order of effectiveness in producing CRs, from most effective (delayed conditioning) to least effective (backward conditioning).

Contingency

Paul develops heartburn every time a spicy meal is consumed, whereas Justin develops heartburn only occasionally when consuming spicy food. Which of these men is more likely to select a spicy meal from a restaurant menu? Probably Justin. In both cases, the contiguity between the CS (spicy food) and the US (developing heartburn) is the same: Heartburn occurs a few hours after consuming the spicy food. However, the contingency between these events is not the same. The relation is more reliable (i.e., the contingency is greater) in Paul’s case than in Justin’s case.

Contingency refers to the frequency with which the CS and US occur together versus apart (e.g., Rescorla, 1968).

Contingencies can be positive, negative, or zero. There is a positive contingency between Paul’s eating spicy food (CS) and his developing heartburn (US; the CS and US occur more often together than apart). In contrast, there is a negative contingency between Paul’s taking an antacid (CS) and his developing heartburn (US; the CS and US occur more often apart than together). Finally, there may be a zero contingency between Paul’s eating a steak (CS) and his developing heartburn (US; the CS and US are equally likely to occur together or apart).

Note that contiguity and contingency are related to each other. For example, as contiguity degrades, contingencies start becoming less positive. If the CS and US occur close together and they only occur if the other is presented, both contiguity and contingency will be maximal and stronger CRs will be observed.

Eliminating Conditioned Responses: Extinction

On one occasion, my dog was playing in the backyard with his favorite toy, a red ball, when a construction truck down the street dropped something, scaring him badly. Afterward, he was afraid of his ball. What could I do to make my dog overcome this unreasonable fear? Let’s take a look at the learning situation: A CS (ball) was paired with a US (loud noise). If, as a result of classical conditioning, my dog learned that the CS signaled the occurrence of the fear-producing US, maybe the CR (fear) can be attenuated by teaching him that the CS is not a signal for US occurrence. That is, if he was to experience the CS without the US, then he could come to expect no US to follow the CS. After allowing my dog to play with his ball for a few days without any loud-noise incidents, he moved from reluctantly approaching the ball (strong fear CR) to happily playing with it (weak or no fear CR).

Presenting the CS without the US (i.e., CS-no US) following acquisition of the CR through CS-US pairings is known as extinction. Extinction is a type of learning; the subject is learning that the CS no longer signals the US. Indeed, extinction and acquisition produce changes in behavior that are very similar, although opposite in direction. Just as with acquisition, most of the extinction we observe with CS-noUS training occurs during the first few trials. Thus, extinction curves are also negatively accelerated, but they are the mirror image of acquisition curves because CRs are decreasing rather than increasing (see Figure 33.2).

Extinction eliminates a CR, but it should not be confused with eliminating learning. Sometimes, the CR may return after extinction has taken place. For example, I had some work done on my backyard and my dog could not play with his ball for a few weeks. When I presented him with the ball again, he was somewhat reluctant to approach it and play with it. That is, somehow, without further conditioning, the fear CR that had undergone extinction returned. This phenomenon is known as spontaneous recovery, and it can be defined as a dissipation of extinction due to the passage of time (Pavlov, 1927). But time is not the only way in which extinguished responses “recover,” or return after extinction. Sometimes, returning to the environment in which the CS-US association was acquired is enough to bring the CR back (environmental stimuli are usually known as contexts). For example, my dog acquired fear of his ball in my backyard (Context 1). If I had conducted the extinction treatment in the park (Context 2) until he happily played with his ball, I might have seen some fear CRs when presenting him with the ball in my backyard (Context 1). Thus, even though a CR has undergone extinction, it could return if the subject is taken back to the context in which the response was acquired. This return of a response due to exposure to the CS in a context other than the extinction context is known as renewal (Bouton & Bolles, 1979)

To Respond Or Not To Respond: Excitation And Inhibition

So far, we have covered the main conditions determining the development of CRs resulting from the CS signaling the occurrence of the US. However, subjects can also learn that a CS signals the omission of a US. When the CS signals US delivery, we talk about excitatory classical conditioning or conditioned excitation (presentation of the CS “excites” the production of a CR). In contrast, when the CS signals US omission, we talk about inhibitory classical conditioning or conditioned inhibition (presentation of the CS “inhibits” the production of a CR). This section briefly describes the procedures used to produce and measure conditioned inhibition.

Procedures That Yield Conditioned Inhibition

Pavlov’s Procedure

In this procedure, first described by Pavlov (1927), the researcher pairs a CS with the US to create a conditioned excitor (i.e., a CS that produces a CR). These trials take the form of CSexc-US. In other trials, a second CS (CSinh) is presented together with CSexc and the pair is not followed by the US. These trials take the form of CSexcCSinh-noUS. Thus, subjects learn that CSexc predicts the US and they produce CRs when CSexc is presented. But they also learn that whenever CSinh is present, no US will be delivered, even if CSexc is also present. Thus, the CR that should be produced by CSexc is not observed because of the presence of CSinh. That is, the presence of CSinh attenuates the CR that would otherwise be elicited by CSexc (see Figure 33.4). This procedure is commonly used to produce conditioned inhibition and, for that reason, it is sometimes referred to as the standard procedure.

All of us have been subject to the Pavlov procedure for producing conditioned inhibitors in our daily lives. For example, when I call my dog and say “Dinner!” (CSexc) he soon gets a meal (US), and this food makes him salivate profusely (UR). With repetition, he has come to salivate profusely (CR) whenever he hears the word “Dinner!” However, he knows that if I say “Dinner!” when we are at the dog park (CSinh) he does not salivate because he has come to realize that a meal is at least one hour away (i.e., no US follows). Thus, the situation involves CSexc-US (“Dinner!” signaling food) trials and CSexc CSinh – noUS (“Dinner!” + dog park signaling no food) trials. As a result of this training, CSexc becomes excitatory (it produces the salivation CR) and CSinh becomes inhibitory (it does not produce the CR).

Other Procedures

There are other types of training that may result in conditioned inhibition. The inhibition resulting from these procedures is not as robust as that resulting from the standard and negative contingency procedures; thus, they are not that widely used. However, it is worth mentioning that the use of a negative contingency (presenting the CS and US more often apart than together; Rescorla, 1968) can also result in the development of inhibition because subjects learn that the presence of the CS signals the absence of the US. Similarly, backward conditioning can result in the development of conditioned inhibition to the CS. Although a few US-CS pairings lead subjects to produce a CR whenever the CS is presented (subjects act as if they know the US is expected sometime around the CS), many US-CS pairings lead subjects to realize that the CS does not signal US delivery but rather US termination (Heth, 1976). Thus, subjects come to expect no US when the CS is presented, and inhibition develops.

Figure 33.4 Pavlov’s (standard) procedure for producing conditioned inhibition. As a result of receiving both trial types during training, CSinh comes signal US omission and consequently inhibits the CR. 

Measurement of Conditioned Inhibition

The Measurement Problem

Assessing the development of conditioned excitation is relatively simple: All we have to do is watch for a CR. However, measuring conditioned inhibition is not that simple. We need to find a way to measure learning of inhibition (i.e., nonproduction) of a response. How can we measure something that does not occur? Researchers have come up with several strategies, the most common of which are known as summation and retardation tests.

Summation Tests for Conditioned Inhibition

Conditioned inhibitors inform subjects that an expected US will not be delivered. Thus, they should attenuate expectation of US delivery when presented together with an excitor. That is, if we present subjects with an excitatory CSexc alone, they should exhibit a CR of a certain magnitude. However, if we present subjects simultaneously with excitatory CSexc and inhibitory CSinh (i.e., CSexcCSinh), the magnitude of CR that we observe to CSexc should be dramatically reduced. Thus, if my saying the word “Dinner!” (CSexc) makes my dog salivate (CR), but saying the word “Dinner!” at the dog park (CSinh) does not, we can begin to assume that the dog park acts as an inhibitor of the salivation CR. Importantly, the CSexc that we use for summation testing can be different from the one used during training. To test this assumption, I can use a different word that also produces the salivation response such as “Breakfast!” (CSexc). If using this word in the dog park results in little salivation, we can conclude that our CSinh, the dog park, is indeed a conditioned inhibitor. You can conceptualize summation as a situation in which CSexc needs to counter the inhibitory power of CSinh before a CR can actually be observed.

Retardation Tests for Conditioned Inhibition

The term retardation refers to speed of acquisition of a CR. It is assumed that, following conditioned inhibition training, an inhibitory stimulus will require more pairings with a US to become a reliable excitor than a stimulus that is neutral at the start of the CS-US pairings. Thus, if I decide to feed my dog (US) at the dog park (CSinh) and at the small field behind my house (CSneutral), it should take longer for him to salivate when getting to the dog park (a CS that signals US omission) than when getting to the small field (a novel stimulus) behind the house. Salivating when getting to the small field reflects the acquisition of a CS-US association in the absence of inhibition; the delay in salivating when getting to the dog park reflects retarded acquisition. You can conceptualize retardation as a situation in which CSinh needs to overcome inhibition before it can begin acquiring excitation.

So, Which Test Is Definitive?

Neither. Factors other than conditioned inhibition could explain what is observed following summation and retardation tests. Fortunately, the alternative explanations for summation and retardation are mutually exclusive. (See Rescorla, 1969, for elaboration.) Thus, researchers have resorted to something known as the two-test strategy. To consider a CSinh as a true inhibitor, it must “pass” (i.e., prove to be inhibitory with) both a summation test and a retardation test.

Higher-Order Classical Conditioning

So far, we have talked about conditioning situations in which the US is a stimulus that elicits an innate response (i.e., a reflex) such as food producing salivation or spoiled food producing stomach illness. But that is not the end of all conditioning. Indeed, most of our conditioning experiences involve learning about stimuli that do not produce innate, reflexive responses. Let us explain this with an example. Mary (CS) broke up (US) with Steven in the fall, which made him sad (UR). Whenever Steven sees Mary (CS), he feels angry (CR). In the spring, Steven and Mary are taking a class together. He sees Mary talking to Julia every day. Now he also feels angry whenever he sees Julia. Notice that in this example, Julia’s presence has not been paired with any unpleasant event that should result in elicitation of the anger CR. However, she has become associated to Mary, a CS that already elicited the CR (see Figure 33.5).

Higher-order conditioning occurs whenever a stimulus becomes a CS because it has been paired with another CS that already elicits a CR. In our example above, Mary is a first-order CS because it has a first-degree association to the US (it is only one step removed from the US). In contrast, Julia is a second-order CS because it has a second-degree association to the US (it is two steps removed from the US). Third, fourth, and other higher orders can be conditioned by pairing a new CS with the previous order CS (e.g., pairing Julia with Stella would make Stella a third-order CS).

Do CS-US Pairings Always Result in CRs?

In a word, the answer to this question is no. Sometimes, you will not observe a CR even if the CS and US are repeatedly paired. Most of these situations can be grouped into situations in which the CS or US has become too familiar and situations in which another stimulus has become a better or more reliable predictor of the US.

Situations In Which The CS Or US Have Become Too Familiar

It seems counterintuitive, but if a subject is too familiar with the CS or US, conditioning is not as effective as if the CS and US were new. For example, cancer patients tend to develop aversions (CRs) to foods (CSs) consumed around the time of their chemo or radiotherapy treatments (US) because these treatments make them feel very nauseous. Interestingly, they seem to take longer to develop aversions to highly familiar foods, like bread, than to less familiar foods. Situations like this, in which the CS is repeatedly presented alone before the CS-US pairings, reflect the so-called CS-preexposure effect (also known as latent inhibition; Lubow & Moore, 1959). In other situations, it is not the CS but the US that is too familiar. Thus, a cancer patient undergoing chemotherapy treatment is frequently exposed to chemicals (US) that result in nausea (UR). Later in treatment, this patient may have a hard time realizing that nausea is related only to receiving a red chemical and not a yellow chemical (CSs) because in her experience the nausea always occurs, even if nothing predicts it. This situation reflects the so-called US-preexposure effect (Randich & LoLordo, 1979).

Thus, if either the CS or the US is repeatedly presented alone before the CS-US pairings take place, acquisition of the CS-US association will exhibit retardation (i.e., delay in producing CRs when presented with the CS). Note that this retardation is functionally equivalent to the retardation that follows conditioned inhibition (see the Measurement of Conditioned Inhibition section); however, conditioned inhibition is not assumed to develop in the preexposure situations because preexposed CSs do not “pass” summation tests for conditioned inhibition (i.e., they do not conform to the two-test strategy; Rescorla, 1971).

Figure 33.5      Higher-Order Conditioning.

NOTES: CS1 (Mary) represents the first-order CS, which is paired with the US and consequently produces a CR. CS2 (Julia) represents the second-order CS, which is paired with CS1 and consequently produces a CR.

Situations in Which Another Stimulus Is a Better or More Reliable Predictor of the US

In all learning situations we encounter more than one stimulus that can become associated to the US. In most of these situations, however, the great majority of the stimuli are somewhat irrelevant to the situation, are very familiar to the subject, or go unnoticed by the subject. Among those stimuli that the subject notices, there are differences in the degree of conditioning they acquire. Theorists usually say that these stimuli compete for association with the US and call the situations described below stimulus competition.

In a Halloween haunted house, a young child is scared by a screeching bat (CShigh) and a quiet spider (CSlow) that suddenly jump out of a pantry (US). Later on, he seems scared of bats but not spiders. Potentially, the characteristics of the CSs made a difference in this learning experience: One of the two CSs, the bat, was more salient than the other, the spider. Usually, when one of the CSs that predict the US is more salient than the others, the salient CS tends to acquire CR-eliciting properties that the other CSs do not acquire. This phenomenon is known as overshadowing (Pavlov, 1927). The CShigh is known as the overshadowing CS, whereas the CSlow is known as the overshadowed CS. Why overshadowing occurs is still under debate. Some researchers say that subjects simply attend to CShigh and ignore CSlow, whereas others say that when subjects have to produce a CR they look at the learning experience and select the best predictor of the US (due to salience, this would be CShigh). Whatever the theoretical explanation, overshadowing is a reliable phenomenon observed in multiple situations.

Imagine that the same child went to a haunted house the previous year and was terrified of a spider (CSold) that fell off the ceiling onto his head. Now, when exposed to the spider (CSold) and the bat (CSnew), the kid fears the spider and not the bat. In this case, due to prior experience, the spider (CSold) has become a better predictor of a fear-producing US. The added stimulus, the bat, is then disregarded as a predictor of the US because the already established predictor, the spider, is present. In these types of situations, we say that the previous experience with the spider (CSold) predicting the US resulted in blocking of learning that the bat (CSnew) also predicted the US (Kamin, 1968). Just as in the case of overshadowing, there are multiple theoretical explanations of blocking; despite their differences, all of them are based on the idea that CSold is viewed by subjects as a more reliable predictor of the US than CSnew.

Biology Versus Experience: Some Constraints On Learning

Pavlov suggested that classical conditioning could be somewhat arbitrary. Indeed, he suggested that any stimulus could become associated to any US if they were paired. However, that is not always the case.

Subjects’ biology takes a primary role when determining whether two stimuli will become associated. These biological constraints on learning are viewed as a result of the evolutionary history of the organism, and they reflect the most advantageous way to adapt to their ecological niche. Thus, some situations benefit from the belonging-ness between the CS and US (biologically, they are meant to be associated), and few or even one CS-US pairing result in strong CRs. This is also known as preparedness (animals’ readiness to acquire some associations faster than others).

The issue of belongingness was beautifully investigated by John Garcia and Robert Koelling in 1966. In their preparation, rats were presented with a drinking tube that delivered flavored water. Additionally, every time the animal extended its tongue to drink from the tube, a light and sound were turned on. Thus, the experience of the animals was of “bright-noisy-flavored water”; this constituted CSbnf. Then, half of the animals were exposed to radiation, which made them ill to their stomach (USradiation). The other half received electrical shock immediately after drinking from the tube (USshock). Then, each of these two groups was again divided in half. Some of the animals received the “bright-noisy” component of the CS (CSbn; plain water accompanied by the light and sound), whereas the remaining animals received the flavor component of the CS (CSf; flavored water with no light or sound). The procedure of the experiment is summarized in Figure 33.6.

The question was which subjects would refuse to drink from the tube? To anticipate the answer to this question, you must think about the world of a rat, which is composed mostly of dark burrows. If you were a rat, how would you find food in your burrow? Probably through smell. And how would you avoid danger? Probably by carefully listening to sounds and watching out for drastic changes in luminosity of your environment. After considering this, the results of the study will not seem so surprising: Rats that received CSbnf-USradiation pairings refused to drink from the spout only when presented with flavored water (CSf). In contrast, rats that received CSbnf USshock pairings refused to drink from the spout only when presented with the light and sound cues (CSbn). Thus, when it came to avoiding illness, they used the cues that they would normally use in their environment to determine whether something is edible—namely, smell and taste. However, when it came to avoiding danger, they used as cues sound and changes in illumination. These basic observations apply across species and, as we will see in the final section of this research-paper, they are prevalent in many daily situations.

Figure 33.6      Schematic representation of Garcia and Koelling’s (1966) study.

Classical Conditioning In Action: Development And Treatment Of Fears And Phobias

In 1920, John B. Watson and his assistant Rosalie Rayner provided the first empirical evidence that fears can be acquired through classical conditioning. Their subject, 11-month-old Albert, was allowed to play with a white rat (CS). While Albert was playing with the rat, a loud noise (US) occurred in the background. Albert became startled and cried when the loud noise occurred in the background (UR). After several CS-US pairings, Albert was presented with the rat and no noise occurred in the background (this was done to assess the strength of the CR). Albert cried and tried to get away from the rat (fear CR). Furthermore, this fear response was observed also when presented with other stimuli that somehow resembled the rat: He was fearful of other animals (dog, monkey, and rabbit) and of white “fluffy” things (Santa Claus mask). That is, the fear CR generalized to other, similar stimuli.

The “little Albert” study exemplifies the origin of most fears and phobias: an event that initially did not produce fear can become fear-producing when paired with another event that unconditionally produces a fear response. Note that most people who experience phobias do not remember the conditioning episode that got them started. However, that does not undermine the fact that classical conditioning may be at the root of that particular phobia.

Observational Learning and the Development of Fear

The principle of belongingness suggests that not all CS-US pairings will result in the development of phobias. We are better prepared to fear some things (e.g., spiders, snakes, and heights) than others (e.g., fruits, rocks, and flowers), probably because our evolutionary history made us more attuned to danger in some situations. (Note that with an intense enough experience, some people may develop fear of fruits, rocks, and flowers.)

An extraordinary example of this principle was provided by Susan Mineka and her colleagues (e.g., Mineka & Ben Hamida, 1998). They presented a wild-reared rhesus monkey (the model) with two objects, a toy snake and a toy flower, and videotaped his reactions. This monkey had experience with both snakes and flowers and exhibited strong fear reactions to the snake but not to the flower. Then, they presented lab-reared monkeys (the observers), which had no experience with snakes, with the videotapes. For some observers, the tape was of the actual model-snake and model-flower encounters. Then, the observers were presented with the toy snake and the toy flower and, not surprisingly, they exhibited fear of the snake but not the flower. That is, observational learning of the fear reaction had taken place. Interestingly, other observers were presented with edited tapes in which the snake and flower had been digitally switched (thus, the model exhibited fear of the flower but not the snake). When presented with the toy flower and the toy snake, these observers displayed fear of neither object. That is, monkeys (like humans) are predisposed to fear snakes (but not flowers) and a single observational experience with a snake (but not a flower) is enough to trigger fear responses. It is believed that observational learning is at the root of many common fears.

Classical Conditioning and the Treatment of Fears and Phobias

So far, we have established that CS-US pairings may be the cause of common fears and phobias. How can we get rid of a CR established through CS-US pairings? The most common procedure is extinction (presenting the CS without the US to attenuate the CR). In therapeutic settings, this procedure is known as exposure therapy, and it basically consists of presenting the subject with the feared object repeatedly to gradually attenuate the fear response. Although there are some techniques that expose subjects to the CS for long periods of time without allowing them to escape the situation (known as hooding, Baum, 1970), most therapists expose subjects to the CS gradually, starting with asking the subject to imagine the object and gradually presenting more realistic versions of the object (e.g., pictures, models, etc.) until the subject manipulates the actual feared object. Another commonly used technique involves conditioning an opposite CR to the object, a procedure known as systematic desensitization (Wolpe, 1969), which is based on the classical conditioning principle of counterconditioning. For example, if a subject fears a dog, a picture of a dog will be used as a CS paired with a US of relaxation. Because relaxation and fear are incompatible responses, the relaxation response will eventually overcome and replace (i.e., counter) the fear response.

A major problem with these techniques is that relapse (the return of fear) is very prevalent. The processes of renewal and spontaneous recovery described previously are some of the major sources of relapse. Current research is trying to identify the major variables determining the return of extinguished responses, as well as the best strategies to prevent relapse.

Summary

Pavlov’s studies demonstrated that even basic, reflexive responses can come under control of experience. Indeed, classical conditioning is prevalent in many aspects of daily life, including the development of emotional responses, food preferences and aversions, and development of fears and phobias. Conditioned responses (CRs) can be produced through CS-US pairings, eliminated by exposing subjects to the CS without the US (CS-noUS trials), or inhibited in situations in which a CSinh signals the omission of an otherwise expected US. Importantly, CRs can be transferred to other, novel CSs just by pairing them with a CS previously paired with a US; thus, learning can occur even in the absence of USs. Conditioning is most effective when the CS and US are relatively novel, occur in close proximity, occur reliably with each other, and occur intensely enough to prevent overshadowing by other stimuli. But experience is limited by biology, and some associations are easier to form than others. These principles allow us to better understand which stimuli in the environment are more likely to control the behavior of organisms, and help us devise better strategies for acquisition and elimination of behaviors through classical conditioning.

References:

1. Baum, M. (1970). Extinction of avoidance responding through response prevention (flooding). Psychological Bulletin, 74, 276-284.
2. Bouton, M. E., & Bolles, R. C. (1979). Contextual control of the extinction of conditioned fear. Learning and Motivation, 10, 445-466.
3. Domjan, M. (2003). The principles of learning and behavior. Belmont, CA: Wadsworth/Thomson.
4. Escobar, M., & Miller, R. R. (2004). A review of the empirical laws of basic learning in Pavlovian conditioning. International Journal of Comparative Psychology, 17, 279-303.
5. Estes, W. K., & Skinner, B. F. (1941). Some quantitative properties of anxiety. Journal of Experimental Psychology, 29, 390-400.
6. Garcia, J., & Koelling, R. A. (1966). Relation of cue to consequence in avoidance learning. Psychonomic Science, 4, 123-124.
7. Gunther, L. M., Miller, R. R., & Matute, H. (1995). CSs and USs: What’s the difference? Journal of Experimental Psychology: Animal Behavior Processes, 23, 15-30.
8. Hearst, E. (1975). Pavlovian conditioning and directed movements. In G. Bower (Ed.), The psychology of learning and motivation (Vol. 9, pp. 215-262). New York: Academic Press.
9. Heth, C. D. (1976). Simultaneous and backward fear conditioning as a function of number of CS-UCS pairings. Journal of Experimental Psychology: Animal Behavior Processes, 2, 117-129.
10. Hollis, K. L. (1997). Contemporary research on Pavlovian conditioning: A “new” functional analysis. American Psychologist, 52, 956-965.
11. Kamin, L. J. (1965). Temporal and intensity characteristics of the conditioned stimulus. In W. F. Prokasy (Ed.), Classical conditioning (pp. 118-147). New York: Appleton-Century-Crofts.
12. Kamin, L. J. (1968). “Attention-like” processes in classical conditioning. In M. R. Jones (Ed.), Miami Symposium on the Prediction of Behavior: Aversive stimulation (pp. 9-31). Miami, FL: University of Miami Press.
13. Lubow, R. E., & Moore, A. U. (1959). Latent inhibition: The effect of nonreinforced preexposure to the conditioned stimulus. Journal of Comparative and Physiological Psychology, 52, 415-419.
14. Matzel, L. D., Held, F. P., & Miller, R. R. (1988). Information and expression of simultaneous and backward associations: Implications for contiguity theory. Learning and Motivation, 19, 317-344.
15. Mineka, S., & Ben Hamida, S. (1998). Observational and non-conscious learning. In W. T. O’Donohue (Ed.), Learning and behavior therapy (pp. 421-429). Needham Heights, MA: Allyn & Bacon.
16. O’Donohue, W. T. (1998). Learning and behavior therapy. Needham Heights, MA: Allyn & Bacon.
17. Pavlov, I. P. (1927). Conditioned reflexes. London: Oxford University Press.
18. Randich, A., & LoLordo, V. M. (1979). Preconditioning exposure to the unconditioned stimulus affects the acquisition of a conditioned emotional response. Learning and Motivation, 10, 245-277.
19. Rescorla, R. A. (1968). Probability of shock in the presence and absence of CS in fear conditioning. Journal of Comparative and Physiological Psychology, 66, 1-5.
20. Rescorla, R. A. (1969). Pavlovian conditioned inhibition. Psychological Bulletin, 72, 77-94.
21. Rescorla, R. A. (1971). Summation and retardation tests of latent inhibition. Journal of Comparative and Physiological Psychology, 75, 77-81.
22. Rescorla, R. A., & Cunningham, C. L. (1979). Spatial contiguity facilitates Pavlovian second-order conditioning. Journal of Experimental Psychology: Animal Behavior Processes, 5, 152-161.
23. Sclafani, A. (1997). Learned controls of ingestive behaviour. Appetite, 29, 153-158.
24. Shanks, D. R. (1994). Human associative learning. In N. J. Mackintosh (Ed.), Animal learning and cognition (pp. 335-374). London: Academic Press.
25. Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions. Journal of Experimental Psychology, 3, 1-4.
26. Wolpe, J. (1969). The practice of behavior therapy. New York: Pergamon Press.

See also:

• Psychology Research Paper Topics
•  Psychology Research Paper Examples

Free research papers are not written to satisfy your specific instructions. You can use our professional writing services to order a custom research paper on any topic and get your high quality paper at affordable price.