Mazur Chapter 3: Basic Principles of Classical Conditioning Flashcards
Basic Terminology
To conduct a typical experiment in classical conditioning, an experimenter first selects some stimulus that reliably elicits a characteristic response
The stimulus of this pair is called the unconditioned stimulus (US), and the response called the unconditioned response (UR)
The term unconditioned is used to signify that the connection between the stimulus and response is unlearned (innate)
In Pavlov’s experiment, the US was the presence of food in the dog’s mouth, and the UR was the secretion of saliva
The third element of the classical conditioning paradigm is the conditioned stimulus (CS), which can be any stimulus that does not initially evoke the UR
In Pavlov’s experiment, the CS was a bell
The term conditioned stimulus indicates that is only after conditioning has taken place that the bell will elicit the response of salivation
Any salivation that occurs during the CS but before the US is referred to as a conditioned response (CR), since it is only because of the conditioning procedure that the bell now elicits salivation
The two components of the initial stimulus-response pair are the US and the UR
Through the procedures of classical conditioning, a novel stimulus, the CS, begins to elicit responses of its own, and these responses to the CS are called CRs since they are learned, or conditioned, responses
Much of the research on classical conditioning has been conducted with a small number of conditioning preparations – conditioning situations using a particular US, UR, and species of subject
o E.g. eyeblink conditioning, condition suppression, skin conductance response
Eyeblink Conditioning
Conditioning of the eyeblink reflex has been studied with humans, rabbits, rats and other animals
The US is a puff of air directed at the eye, and the UR is the eyeblink
The CS may be a light, tone or some tactile stimulus such as a vibrational experimental chamber, and the duration of the CS is typically about one second
Like the UR, the CR is an eyeblink, but its form may be different (smaller and more gradual blink)
Eyeblink conditioning often requires a large number of CS-US pairings
Conditioned Suppresion
aka “Conditioned Emotional Response” (CER)
Subjects are usually rats
The US is an aversive event such as a brief electric shock delivered to the metal bars that form the floor of the experimental chamber
The UR to shock may include several different behaviors
The measure of conditioning in this situation is the suppression of ongoing behavior when the CS (which signals that a shock is forthcoming) is presented
The duration of the CS is generally much longer in the conditioned suppression procedure – one minute or more is typical
The shock comes at the end of the of 1-minute CS and lasts about 1 second
**Conditioning takes place in far fewer trials than in the eyeblink procedure, perhaps partly because the shock is more intense than air puffs
The Skin Conduction Response (SCR)
a.k.a. electrodermal response, a.k.a. galvanic skin response
Subjects are usually human
The SCR is a change in the electrical conductivity of the skin
To measure a person’s SCR, two coin-shaped electrodes are attached the palm, and electrodes are connected to a device that measures momentary fluctuations in the conductivity of the skin caused by small changes in perspiration
The conductivity of the skin is altered by emotions such as fear or surprise
Electric shock is a stimulus that reliably produces a large increase in skin conductivity
A similar increase in conductivity can be conditioned to any CS that is paired with shock
Taste-Aversion Learning
Subjects are usually rats
CS is the taste of something the subject eats or drinks
After eating or drinking the animals given an injection of a poison (the US) that makes it ill
Several days later, after the animal has fully recovered from its illness, it is again given the opportunity to consume the substance that served as the CS
The usual result is that the animal consumes little or none of this food
Thus, the measure of conditioning is the degree to which the animal avoids the food
Some psychologists have suggested that taste-aversion learning is not an ordinary example of classical conditioning, but that it violates some of the general principles that apply to classical conditioning
Taste-aversion often develops after just one conditioning trial and this rapidity of conditioning is advantageous for certain theoretical questions
Taste aversion is something that many people experience at least once in their lives
An aversion may develop even if the individual is certain that the food was not the cause of the subsequent illness
Pavlov’s Stimulus Substitution Theory
Through repeated pairings between CS and US, the CS becomes a substitute for the US, so that the response initially elicited only by the US is now also elicited by the CS
Today, very few conditioning researchers believe the theory to be correct
The CR is almost never an exact replica of the UR
Not all parts of the UR to a stimulus become part of the CR
• e.g., a well-trained CS such as a bell will elicit salivation, but it will generally not elicit the chewing and swallowing responses
A CR may include some response that are not part of the UR
• e.g., sometimes a dog moves its entire body closer to the ringing bell
The CR is someitmes opposite in direction to the UR
• e.g. decreased heartrates of guinea pigs to a CS paired with a shock
In order to amend this theory, it should be acknowledged that only some components of the UR are transferred to the CR
Some components of the UR may depend on the physical characteristics of the US, and they will not be transferred to a CS with very different physical characteristics
Also, A CS such as a bell frequently elicits URs of its own, and these may become part of the CR
• e.g., when the dog hears the bell, and may exhibit an orienting response
In short, the form of the CR may reflect both the UR to the US (e.g. salivation, but not chewing or swallowing) and the UR to the CS itself (e.g. orienting toward the sound of the bell)
Possibly the strongest argument against stimulus substitution theory arises from the finding that in some cases the direction of the CR is opposite to that of the UR
Conditioned responses that are the opposite of the UR are called conditioned compensatory responses
For all these reasons, it is often difficult to predict in advance what the CR will look like in a specific instance – it may resemble the UR, or it may be very different
sign-tracking theory
Animals tend to orient themselves toward, approach, and explore any stimuli that are good predictors of important events, such as the delivery of food
conditioned compensatory responses
Conditioned responses that are the opposite of the UR
Pavlov’s “Centers” of the brain
Pavlov proposed that there are specific parts of the brain that become active whenever a US is presented – the “US center” of the brain
Similarly, for every different CS, there is a separate “CS center”, which becomes active whenever that particular CS is presented
Pavlov also assumed that for every UR there is part of the brain that can be called a “response center”, and it is the activation of this response center that initiates the neural commands that ultimately produce the observed response
Since the US elicits the UR without any prior training, Pavlov assumed that there is an innate connection between the US center and the response center
S-S vs S-R
Pavlov proposed that somehow an association develops during the course of classical conditioning, so that now the CS produces activity in the response center, and the CR is observed
There are at least two types of new associations that would give the CS the capacity to elicit a CR
S-R association—direct association between the CS center and the response center is formed during conditioning (stimulus and response “S-R”)
S-S association—a direct association between the CS center and the US center is formed during conditioning (CS-US)
Later, when the CS is presented, the CS center is activated, which activates the US center through the newly formed association, which in turn activates the response center
Pavlov tended to favor the S-S position
Attempts to study S-R vs S-S connections
Rescorla (1973) used the following reasoning: If the S-S position is correct, then after conditioning, the occurrence of a CR depends on the continued strength of two associations:
- The learned association between the CS center and the US center
- The innate association between the US Center and the response center
If the US-response connection is somehow weakened, then this should reduce the strength of the CR, since the occurrence of the CR depends on this connection
If the S-R position is correct, however, the strength of the CR does not depend on the continued integrity of the US-response association, but only on the direct association between the CS center and the response center
Rescorla used the condition suppression procedure with rats
A conditioned suppression of lever pressing would develop in response to any CS paired with the noise
But the noise was also susceptible to habituation if it was repeatedly presented
Two groups of rats were classically conditioned in an identical matter with a light as the CS and the noise as the US
In phase 2, the habituation group received many presentations of the noise by itself, in order to habituate the rats’ fear of the noise
• [The Control group received no stimuli]
This technique of decreasing the effectiveness of the US after excitatory CS has been created is called US devaluation
He found high levels of suppression to the light in the control group, but significantly lower levels of suppression in the habituation group
He concluded that the strength of the CR depends on the continued strength of the US-response association, as predicted by the S-S position, but not the S-R position
US devaluation
Technique of decreasing the effectiveness of the US after excitatory CS has been created
e.g. Habituating rats to loud noise after light has been paired, light CS+ loses excitatory strength
Acquisition
The part of a conditioning experiment in which the subject first experiences a series of CS-US pairings, and during which the CR gradually appears and increases in strength is called the acquisition phase
Strong USs also usually result in faster conditioning
This is also true of the intensity of the CS (e.g. loud tone, bright light)
Asymptote
THe maximum level of conditioned responding that is gradually approached as conditioning proceeds
The size or intensity of the US has a major influence on the asymptote of conditioning
Extinction
Technique for producing the reduction and eventual disappearance of the CR
[The passage of time has relatively little effect on the strength of a CR]
Extinction involves repeatedly presenting the CS without the US
Though extinction results in elimination of the CR, it does not simply reverse the effects of the previous acquisition phase
At least three different phenomena show that whatever association was formed during acquisition is not erased during extinction:
Spontaneous recovery
Disinhibition
Rapid reacquisition
In summation, extinction can cause a CR to disappear, and after repeated extinction sessions spontaneous recovery may disappear, but the subject will never be exactly the same as before the conditioning began
Spontaneous Recovery
After extinction produces no CR’s, often the next day a reappearance of CRs occurs, which Pavlov treated as proof that CS-US association is not permanently destroyed in an extinction procedure
If extinction serves to undo or erase learning that occurred in acquisition, why would CRs spontaneously reappear for the conditioning trials?
If more time elapsed between the first and second extension sessions, more spontaneous recovery is observed
Inhibition Theory
After extinction is complete, the subject is left with two counteracting associations
- CS-US association formed during acquisition is called an excitatory association because through this association the CS now excites, or activates the US center
- A parallel but inhibitory association develops during extinction
When extinction is complete, the effects of the excitatory and inhibitory associations cancel out, so that the US center is no longer activated by the presentation of the CS
The inhibitory CS-US association is strong enough to counteract the excitatory association completely, so that no CRs are observed
However, Pavlov proposed that inhibitory associations are more fragile than excitatory associations, and they are more severely weakened by the passage of time
Therefore, the reappearance of CRs are observed due to the weakened inhibitory association no longer fully able to counteract the excitatory association
Further extinction trials strengthen the inhibitory association, and CRs once again disappear
The amount of spontaneous recovery becomes smaller and smaller until it no longer occurs
According to the inhibition theory, this happens because the inhibitory association becomes progressively stronger with repeated extinction sessions
Other theories of spontaneous recovery
*The organism simply stops processing or paying attention to the CS
o When returned to the conditioning chamber, the attention to the CS is revived leading to spontaneous recovery of CRs
*The CS becomes an ambiguous stimulus because it has been associated both the US and then with the absence of the US
o The ambiguity relies on context for meaning, and the presence of a buzzer, for example, may serve to reduce confusion
Disinhibition
The presentation of a distracting stimulus disrupts the fragile inhibition that supposedly develops during extinction
• e.g., a CS (bell) no longer evokes any salivation → a novel stimulus such as a buzzer is presented a few seconds before the bell → the bell may once again elicit a CR of salivation
According to the inhibition theory, the more stable excitatory association is less affected by the distracting stimulus than is the inhibitory association, and the result is a reappearance of the CR
Rapid Reacquisition
Similar to Ebbinghaus’ “savings”
If a subject receives an acquisition phase, and extinction phase, and then another acquisition phase with the same CS in the same US, the rate of learning is substantially faster in the second acquisition phase → the reacquisition phase
Conditioned Inhibition
If it can be shown that a CS prevents the occurrence of a CR, or that it reduces the size of the CR from what it would otherwise be, then this CS is called an inhibitory CS or a conditioned inhibitor (CS-)
e.g. – using two different CSs, a buzzer and the light
o In the first phase, the buzzer is paired with food until the dog salivates at the sound of the buzzer
o The buzzer can now be called an excitatory CS (CS+) because it regularly elicits a CR
o In the second phase, the dog received two types of trials, some are exactly like the first, and some trials have both the buzzer and the light presented simultaneously, but no food is delivered
o The simultaneous presentation of two or more CSs like these is called a compound CS
o At first, compound CS may elicit the CR
As phase 2 continues, however, the dog will eventually salivate on trials of the buzzer alone, but not on trials with both the buzzer and the light
If the light is truly a conditioned inhibitor, it should have the capacity to reduce the salvation produced by any CS, not just by the buzzer with which it was originally presented
Summation: A stimulus will become a conditioned inhibitor if it reliably signals the absence of the US in a context where the US would otherwise be expected to occur
o e.g. Because the light signaled the absence of an otherwise imminent US, it became an inhibitory CS
Summation Test
Testing the combined effects of a known excitatory CS and if possible inhibitory CS
Retardation Test
Method for determining whether a stimulus is inhibitory is to measure how long it takes to turn the stimulus into an excitatory CS
Acquisition should be slowed down with a CS that is initially inhibitory
generalization
he transfer of the effects of conditioning to similar stimuli
discrimination
the opposite of generalization, in which a subject learns to respond to one stimulus but not to a similar stimulus
The Importance of Timing in Classical Conditioning
The timing of events can affect:
o How strong the conditioning will be
o Whether a CS will become excitatory or inhibitory
o Exactly when the CR occurs
short-delay conditioning
The CS begins a second or so before the US
*Usually produces the strongest and most rapid conditioning
simultaneous conditioning
The CS and US begin at the same moment
conditioned responding is much weaker than in short-delay conditioning
possibly due to lack of predictability if presented at the same time
the predictiveness of a CS is an important determinant the degree of conditioning and whether this conditioning is excitatory or inhibitory
CS Predictiveness
To the extent that a CS is a good predictor of the presence of the US, it will tend to become excitatory
To the extent that a CS is a good predictor of the absence of the US, it will tend to become inhibitory
trace conditioning
The CS and US are separated by some time interval in which neither stimulus is present
[since CS is no longer physically present, the subject must rely on a “memory trace” of the CS if conditioning is to occur]
As the CS-US interval is increased, the level of conditioning declined systematically
long-delay conditioning
The onset of the CS precedes that of the US by at least several seconds, but the CS continues until the US is presented
Like in trace conditioning, the strength of the condition responding decreases as the CS-US interval increases, but the effects are not as pronounced, since the subject does not have to rely on a memory trace of the CS
backward conditioning
CS is presented after the US
Level of conditioning is markedly lower than in simultaneous or short-delay conditioning
The weakness of backward conditioning points to a limitation of the contiguity principle—besides in their temporal proximity, the order of the stimuli is important
*After a sufficient number of trials, a backward CS becomes inhibitory
→The onset of the CS signals a period of time in which the US will be absent
→As long as the backward CS is present, the subject can be certain that no US will occur
temporal coding hypothesis
In classical conditioning, more is learned many simple
association between CS and US
The individual also learns about the timing of these two events
This learning affects when the CR occurs
This hypothesis can explain why CR may occur just before the onset of the US in the long-delay conditioning – the subject has learned that a delay of a certain duration separates the onset of the CS and the onset of the US
Rescorla & Correlation
Based on his results of conditioned suppresion procedures with rats, Rescorla concluded that the traditional view of classical conditioning, which states that the contiguity of CS and US is what causes an association to develop is incorrect
He proposed that the important variable in classical conditioning is not the contiguity of CS and US but rather the correlation between CS and US
If a CS predicts that the US is likely to occur, the CS will become excitatory
If a CS predicts that the US is not likely to occur, the CS will become inhibitory
second-order conditioning
CR is transferred from one CS to another
First-order CS– CS is paired with US
Second-order CS: another CS paired with the first-order CS which elicits the CR, *without ever being directly paired with the US
evaluative conditioning
second-order conditioning in humans
e.g. nonsense syllable repeatedly paired with a positive or negative word (which developed into a CS through language and experience), subjects later give the nonsense syllable a positive or negative rating
e.g. pictures of people’s faces (second-order stimuli) was paired with either positive or negative adjectives (first-order stimuli)
• subject later rated the faces as “liked” if they had been paired with positive adjectives and “disliked” if they had been paired with negative adjectives
[evaluative conditioning has long been used in advertising]
Applications in Behavior Therapy
systematic desensitization
aversive counterconditioning
treatment of nocturnal enuresis (bedwetting)
systematic desensitization
Manly used as treatment for phobias
Patient is exposed to phobic object gradually, so that fear and discomfort are kept to a minimum and extension is allowed to occur
Treatment has three parts:
• construction of a fear hierarchy
• training and relaxation
• gradual presentation of items in the fear hierarchy to the patient
After the fear hierarchy is constructed, the patient is given training in progressive muscle relaxation, (Wolpe 1958)
aversive counterconditioning
developing an aversive CR to stimuli associated with undesirable behavior
The term counterconditioning is used because the technique is designed to replace a positive emotional response to certain stimuli (such as alcohol, drugs, smoking, sexual deviation) with a negative one
Effectiveness is variable
Treatment of nocturnal enuresis (bedwetting)
Bell-and-pad method
• water-detecting devices placed beneath the sheets and a single drop of urine will activate the device during the development of child
Bell is a US that elicits two responses in the child:
• awakening
• tightening of those muscles necessary to prevent further urination
The goal of the procedure is to transfer either or both of these responses to an internal CS – the sensations associated with having a full bladder
By repeatedly pairing a full bladder with the bell, the response of awakening and-or tightening the muscles so as to retain one’s urine should eventually be elicited by the full bladder alone, before the bell sounds
