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Classical Conditioning

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Chapter 4: p139

Focus Questions

What is classical conditioning and how did Pavlov study it?

Ivan Pavlov is the originator of what is now called classical conditioning, a form of learning base primarily on stimuli that causes reflexes, such as salvation in response to food.

What basic procedures are involved in classical conditioning?

In classical conditioning, the stimulus that naturally produces the reflex response is the unconditional stimulus (UCS), which is repeatedly paired with an initially neutral stimulus until the latter becomes the conditional stimulus (CS). What is learned in classical conditioning is a CS-UCS association; the original reflex response is the unconditional response (UCR), and the response produced by the CS is the conditional response (CR).

Classical Conditioning: Definitions


the establishment of a relationship between stimuli and responses, or vice versa.


a relatively permanent change in behavior potential as a result of experience..


a built-in or otherwise automatic response to a specific stimulus.

Classical Conditioning: 

The establishment of a relationship between two stimuli, typically one that evokes a reflex response and one that is initially neutral with regard to this response.

Unconditional stimulus (UCS): 

Any stimulus that automatically and reliably produces a particular response, such as a reflex.  

Conditional stimulus (CS): 

An initially neutral stimulus that comes to elicit a response similar to that elicited by a UCS.

Unconditional response (UCR): 

The automatic response to an unconditioned stimulus.  

Conditional response (CR): 

the learned response to a conditioned stimulus (CS). 


Classical Conditioning

Classical conditioning is a type of learning in which an animal’s natural response to one object or sensory stimulus transfers to another stimulus. This illustration shows how a dog can learn to salivate to the sound of a tuning fork, an experiment first carried out in the early 1900s by Russian physiologist Ivan Pavlov. For conditioning to occur, the pairing of the food with the tuning fork (step 3 in the illustration) must be repeated many times, so that the dog eventually learns to associate the two items.


Chapter 4: Classical Conditioning Phenomena and Applications: p142

Focus Questions

Why is timing of the CS and UCS important in classical conditioning?

Delayed conditioning is the most effective form of classical conditioning. Less effective are simultaneous conditioning and trace conditioning. After conditioning, extinction of the CR occurs when the UCS is discontinued. Allowing time to pass and returning the subject to the apparatus is typically accompanied by spontaneous recovery.


Timing is Everything 

In trace conditioning, the CS precedes and is terminated before the onset of the US. The onset of the CS and the US in trace conditioning is shown in figure a. Only the onset of stimuli influence learning in the present model.

A less effective version of classical conditioning, in which (CS), onset and offset precede (UCS), ), onset.

In delay conditioning, the CS is present throughout the presentation of the US. In the present model, this situation is handled identically to trace conditioning

The most effective version of classical conditioning, in which
(CS) onset precedes
(UCS), and the offset of both stimuli are typically at the same time.

In simultaneous conditioning, the CS and the US are presented at the same time. This does not usually result in any learning.

A less effective version of classical conditioning, in which both (CS), and
onset and offset occur at the same time.

Why is it important for the CS to “predict” the UCS?

The crucial factor in classical conditioning is the consistency with which the CS predicts the occurrence of the UCS.

How do generalization and discrimination work?

Stimulus generalization occurs when a stimulus similar to the original CS also produces CR.

Stimulus discrimination, its complement, occurs when dissimilar stimuli produce lesser CR or none at all.

How does biological predisposition affect classical conditioning?

Biological predispositions are often apparent in classical conditioning. Because of pre-wiring, some CS-UCS associations can be established much more easily that others and some not at all.

Taste aversion experiments provide an example of how biological predispositions affect conditioning. The learning of taste aversion is easy for animals that naturally associate taste with food but difficult to impossible for animals that use other cues, such as visual ones for food.


In the modern view, conditioning can be best explained by the development of expectancies—that is, what animals and humans learn is the expectation that a particular conditioned stimulus (CS) will be followed by an unconditioned stimulus (UCS).

Classical conditioning by past events may account for many of the fears and preferences displayed by human adults—and also for physical symptoms such as unexplained headaches or nausea and the intense desire to return to drug use that is some times displayed by former drug addicts.

  • In Watson and Rayner’s “Little Albert” experiment, the loud sound was the unconditioned stimulus (UCS), the rat was the conditioned stimulus (CS), and a fear response was the (UCR), and the (CR).
  • In the experiment on conditioned illness in rats, the insulin was the unconditioned stimulus (UCS), the light and syringe were the conditioned stimulus (CS), and the coma was the unconditioned response (UCR), and conditioned response (CR).
  • In the experiment on conditioning the immune system in rats, the drug was the unconditioned stimulus (UCS), the novel taste was the conditioned stimulus (CS), and production of the antibodies was the unconditioned response (UCR), and conditioned response (CR).
  • In the experiments on conditioning sexual behavior in rats, normal female odors were the unconditioned stimulus (UCS), the lemon scent was the conditioned stimulus (CS), and sexual arousal was the unconditioned response (UCR), and conditioned response (CR).


Classical Conditioning Phenomena and Applications: Definitions

Delayed Conditioning

The most effective version of classical conditioning, in which CONDITIONED STIMULUS (CS) onset precedes UNCONDITIONED STIMULUS (UCS), and the offset of both stimuli are typically at the same time.

Simultaneous Conditioning

A less effective version of classical conditioning, in which both (CS), and
onset and offset occur at the same time.

Trace Conditioning

A less effective version of classical conditioning, in which (CS), onset and offset precede (UCS), ), onset.


Disappearance of the (CR), upon discontinuance of the (UCS).

Spontaneous Recovery

Reappearance of an extinguished (CR), after the passage of time.

Stimulus Generalization

The tendency of a (CR) to occur to CSs that are similar to the original CS.

Stimulus Discrimination

The tendency of a (CR) to be weaker or not occur to (CS)s that are dissimilar to the original (CS) or that have undergone extinction


What animals and humans learn is the expectation that a particular conditioned stimulus (CS) will be followed by an unconditioned stimulus (UCS).


Ivan Petrovich Pavlov

September 26, 1849 – February 27, 1936

Classical Conditioning was advanced by a serendipitous finding of Ivan Pavlov. The word serendipitous means accidental discovery. Pavlov, a Russian physiologist, was studying digestion when he stumbled on the phenomenon that made him one of the most famous psychologists in the twentieth century. Subsequently, Classical Conditioning is sometimes called Pavlovian Conditioning because it was discovered by Ivan Pavlov.

As a physiologist, it was Pavlov’s ambition to discover the neural mechanisms that control glandular secretions during digestion. Pavlov used dogs as his subjects as he exposed the dogs’ salivary glands and measured the amount of salivation.


Pavlov’s Apparatus: Harness and fistula (mouth tube) help keep dog in a consistent position
and gather uncontaminated saliva samples. They do not cause the dog discomfort. (Carlson, 1997)


Pavlov’s strategy was to study salivary processes in individual dogs over many test sessions. During each session, he placed dry food powder inside the dog’s mouth and then collected the saliva. All went well until the dogs became experienced subjects. After several testing sessions, the dogs began salivating before being fed, usually as soon as they saw the laboratory assistant enter the room with the food powder. What Pavlov discovered was a form of learning in which one stimulus predicts the occurrence of another. In this case, the appearance of the laboratory assistant predicted the appearance of food (Carlson, 1997).

Pavlov designed experiments to discover exactly why the dogs were salivating before being given the opportunity to eat. He suspected that salivation might be triggered by stimuli that were initially unrelated to eating. Somehow, these previously neutral stimuli came to control what is normally a natural reflexive behavior. After all, dogs do not naturally salivate when they see laboratory assistants (Carlson, 1997).

In order to understand what was controlling this unexpected behavior of salivating when the laboratory assistants were seen, Pavlov placed an inexperienced (naive) dog in a harness and occasionally gave it small amounts of food powder. Just prior to placing the food powder in the dog’s mouth, Pavlov sounded a bell, a buzzer, or some other auditory stimulus (Carlson, 1997).

At first, the dog showed only a startle response to the sound. The dog salivated only when the food powder was placed in the dog’s mouth. After only a dozen or so pairings of the bell and food powder, the dog began to salivate when the bell rang (Carlson, 1997).

Placing the food powder in the dog’s mouth was no longer necessary to elicit salivation. When learning took place, the sound by itself was sufficient to elicit salivation. Pavlov, therefore, showed that a neutral stimulus (bell sound) can elicit a response similar to the original reflex (salivation) when the previously neutral stimulus (bell sound) predicts the occurrence of a significant stimulus (food powder) (Carlson, 1997).

Consequently, learning occurred in that there was a CHANGE in behavior due to an association between two stimuli – the Conditioned Stimulus and the Unconditioned Stimulus. This association between the Conditioned Stimulus and the Unconditioned Stimulus is why Classical Conditioning is also called Associative Learning.

Terms Specific to Classical Conditioning

  1. Elicit
  2. Unconditioned Stimulus
  3. Unconditioned Response
  4. Conditioned Stimulus
  5. Conditioned Response

Elicit: Elicit means to produce, cause or evoke a response.

Unconditioned Stimulus (UCS): The prefix “un” means not; conditioned means learned; stimulus means person, place, object, event, or physical energy; therefore, an unconditioned stimulus is any stimulus which does not require learning in order to elicit or cause a behavior.

Unconditioned Response (UCR): An unconditioned response is the response that is automatically elicited, produced, caused or evoked by the Unconditioned Stimulus (UCS). No learning takes place when the UCS is presented. The UCR may be a reflex produced by the UCS. Reflexes are simple, unlearned, involuntary responses.

Conditioned Stimulus (CS): A conditioned stimulus is initially neutral. Initially, the conditioned stimulus is not capable of eliciting, producing, causing, or evoking a conditioned response. After learning takes place, the CS elicits the conditioned response (CR).

Conditioned Response (CR): A conditioned response (CR) is a response that is learned. The learning takes place because the UCS and the CS are associated together. Later, the CS comes to take on a similar capability of eliciting the CR which is similar to the UCR.

Explaining the words “conditioned” and conditional” In the Russian language, Pavlov used the adjective “uslovna” which is more properly translated “conditional” and not “conditioned”. However, with the English translation, the use of the terms conditioned stimulus and conditioned response has become accepted.



Classical Conditioning 

Initially, the bell as a neutral stimulus (NS).

Meat is an unconditional stimulus (US).

Phase l: Before Conditioning (Before Learning)

Before conditioning, two distinctly unrelated stimuli are selected. Pavlov discovered that the meat powder was the stimulus that naturally produced/elicited or caused the salivation. Therefore, Pavlov referred to the meat powder as the Unconditioned Stimulus (UCS). When presented alone, the meat powder produced, elicited, and caused the Unconditioned Response (UCR). The natural salivation produced when the food powder was placed in the dog’s mouth was the Unconditioned Response. The UCR is any response that is naturally caused and does not require learning.

During this phase, Pavlov was faced with demonstrating that the Conditioned Stimulus (the bell tone) did not initially elicit a Conditioned Response prior to learning or before being associated with the UCS. Therefore, Pavlov presented the Conditioned Stimulus (bell tone) alone and the dog did not salivate. At this point, the bell tone is actually a Neutral Stimulus (NS) which becomes the conditioned stimulus (CS).

Meat and bell presented together
(CS + US)

Phase II: Conditioning Phase (Learning Phase)

Next, Pavlov paired the Unconditioned Stimulus and the Conditioned Stimulus (CS). During the Conditioning Phase, the CS (the bell tone) and the UCS (the meat powder) were presented together several times before the CS reliably elicited the CR.

Bell (CS) alone elicits salivation (CR).

Phase III: After Conditioning Phase

To determine if conditioning (learning) occurred, Pavlov presented the Conditioned Stimulus alone and the dog salivated. This CHANGE in behavior towards the bell tone meant learning occurred. Initially, the dog did not salivate to the bell tone. After learning occurred, the dog salivated when the bell tone was presented.

When Classical Conditioning occurs, the CS elicits the CR, subsequently the CS predicts the occurrence of the UCS.

Bell presented without meat many times.

Bell elicits no salivation. 

Phase IV: Extinction Phase

Pavlov observed that a previously learned response (CR) was eliminated by repeatedly presenting the CS without presenting the UCS. When extinction occurred, the CS was no longer capable of producing the CR (salivation). Zimbardo and Gerrig (1999) explained that extinction happens when the CS no longer predicts the UCS.

Here Today, Gone Tomorrow, Back Again!

After the CS (bell tone) has been presented several times without any food forthcoming, the dog’s salivation response extinguished and the dog stopped salivating to the CS (bell tone) alone. However, if the CS is not presented for a period of time and then is presented, the previously learned conditioned response of salivation on hearing the tone alone will return. The dog is displaying spontaneous recovery of the response but may not salivate as much as it did when it was first classically conditioned to the CS (bell tone).

A feature of the Extinction Phase is Spontaneous Recovery which means that the Conditioned Response reappeared after the Conditioned Response had been previously eliminated. Kosslyn and Rosenberg (2003) explained that when a Conditioned Response has been extinguished, the Conditioned Stimulus will again elicit the Conditioned Response, although sometimes not as strongly as before extinction.


Written by Joseph Eulo

May 28, 2008 at 5:36 am

One Response

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  1. i will not reap benefits much from this but my parents will, so thanks a lot
    LOL never could have thought of that, terrific! xxx


    February 22, 2013 at 6:23 pm

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