Describe Rescorla’s research on the predictive value of the conditioned stimulus (CS) in classical conditioning.
Review
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1. In classical conditioning, two stimulus events that repeatedly occur close together in time eventually become associated with one another. Initially, researchers believed that this contiguity (close connection in timing) was the “glue” that allowed the conditioned association to form.
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2. However, research by Robert Rescorla and Allan Wagner demonstrated that there is a strong cognitive component to classical conditioning. Rats quickly and easily learn associations when the conditioned stimulus (CS) consistently and uniquely predicts the arrival of the unconditioned stimulus (US). When the CS has lower predictive value, conditioning takes longer, or doesn’t occur at all.
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3. The word predict is very important in classical conditioning. If a neutral stimulus (NS) comes after the US, no learning occurs, and the NS never becomes a CS. The NS (in this case, a bell) doesn’t allow the dog to anticipate the arrival of the US (the food). The NS by itself will not be able to produce a conditioned response (CR) (drooling).
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4. If one NS (in this case, a horn) always occurs just prior to the US, while a second NS (a bell) sometimes occurs just prior to the US, what will happen? The NS that reliably predicts the US will become a CS, while the other NS will be ignored.
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5. If two NS events always occur just prior to the US, but one of them also occurs at other times when the US doesn’t appear, what will happen? The NS that uniquely predicts the US will become a CS, and the other NS will be ignored.
Practice 1: Information Value: Timing of Events
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In classical conditioning, the timing of the conditioned stimulus (CS) is important. Learning is quicker when the CS and the unconditioned stimulus (US) are close together in time. Robert Rescorla and Allan Wagner demonstrated that the information value of the CS is even more important. We will try to demonstrate that with a simulation of several experiments.
The first experiment involves conditioning an eyeblink. The human participants in this experiment will receive, at random intervals, a puff of air directed at one of their eyes. This air puff is an unconditioned stimulus (US) that automatically produces an unconditioned response (UR)—in this case, an eyeblink. On each conditioning trial, a brief neutral stimulus (NS), a tone, will be presented either just before or just after the air puff. Periodically, we will present the tone without the air puff to see if the tone has become a conditioned stimulus (CS) that can produce an eyeblink, a conditioned response (CR), by itself.
When the tone occurred prior to the air puff, even by as little as a half-second, the tone quickly became a conditioned stimulus (CS) capable of producing an eyeblink on its own. An eyeblink to the tone is a conditioned response (CR).
When the tone occurred after the air puff, or even at the same time as the air puff, the tone never became a conditioned stimulus (CS) capable of producing an eyeblink on its own.
All participants received the tone (NS) in close proximity to the air puff (US), but only when the tone came first did the participants become conditioned to blink to the tone. Why? Because the tone had information value, allowing the participants to predict that the air puff would soon follow.
Practice 2: Information Value: Consistency of Events
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The second experiment involves fear conditioning in rats. The rats in this experiment will receive, at random intervals, a painful electric shock to their paws. The shock is a US that automatically produces a UR of fear and distress. On each of those 20 shock trials, the researchers will turn on a light (NS) one second before the shock occurs. On 10 of the trials, a tone (NS) will sound at the same time that the light turns on. After the 20 conditioning trials, at random intervals, either the tone or the light will turn on, to see whether the rat displays a CR of fear to the tone or light, which would then become a CS.
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It appears that the light became a CS capable of producing fear, but the rats did not develop a conditioned fear of the tone. Why not? Remember that the light occurred on every shock trial, but the tone occurred only half of the time. The light provided more “information value” about the coming shock. The tone was redundant (it provided no unique information), so the rats seemed to ignore the tone.
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Practice 3: Information Value: Unusual Events
Select the SHOW TRIAL SEQUENCE button to learn about an experiment on conditioning the salivary response in dogs.
The final experiment involves conditioning the salivary response in dogs. The hungry dogs in this experiment will receive, at random intervals, a small but delicious food treat. The food is a US that automatically causes the dog to salivate (UR). On each of 20 food trials, the researchers will first open and close the door to the lab room (NS), then blow a whistle (NS), and then present the food (US). After the 20 conditioning trials, at random intervals, the researchers will either open and close the lab room door or whistle, to see whether the dog displays a CR of saliva to the door or the whistle, which would then be called a CS.
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The dogs clearly became conditioned to salivate to the whistle, but the sound of the door did not become a CS. Why not? Because the dogs heard the lab door open and close dozens of times every day, and most of the time the sound of the door had no connection to the arrival of the food treat. Even though the door sound always preceded the treat, the door sound had low information value compared to the whistle, which uniquely allowed the dogs to predict that the food was coming soon.
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Quiz 1
Select the best answer for each question. When both questions have been answered, select the CHECK ANSWER button.
Quiz 2
Select the most likely outcome to answer the question. Then, select the CHECK ANSWER button.