Classical Conditioning 1 & 2
Introduction to Learning
At a more basic level, unconscious, reflexive learning is vital to the survival of a species.
o A child only needs to touch a hot stove once to learn to avoid glowing red elements to prevent pain
Two Types of Learning
There are two important unconscious learning processes: classical conditioning and instrumental
o Classical Conditioning: allows us to associate two related events.
o Instrumental Conditioning: allows us to associate actions and consequences.
The foundation for classical conditioning was done by the famous Russian physiologist: Ivan Pavlov in the
1890’s and 1900’s. (Classical conditioning aka Pavlovian conditioning).
Pavlov was interested in the stages of digestion, which began with salivation in the mouth as food was first
Pavlov made an extraordinary observation: dogs would salivate even before the delivery of food in their
mouth. It was as if an early step in the process of digestion was triggered even before the food stimulus
In Pavlov’s famous experiments, the sound of a metronome signalled to a dog that food was about to be
delivered. Prior to training, the sound of the metronome had no observable effect on the dog’s behaviour.
However, following training, a dog would begin salivating in response to the sound of the metronome alone.
This new behaviour was called a conditional reflex, so called because it was conditional upon training.
Pavlov was technically studying a contingent relationship: the presentation of one stimulus reliably leads to
the presentation of another.
o I.e. A flash of lightning just before you hear the crash of thunder.
When an organism learns the association between a signal and an event, we say that a contingency has
formed between the two stimuli.
Classical Conditioning: the learning of a contingency between a particular signal and a later event that are
paired in time and/or space.
Learning these contingencies is the essence of classical conditioning. When a contingent relationship is
learned, an organism can respond to the signal before the event even occurs.
This conditional response is often prepatory in nature and can promote survival.
o It makes sense to begin salivating in anticipation of arriving food because it can make digestion
o Antelope surviving by learning to flee when they spot cues to indicate a lion’s presence (sounds,
The Unconditional Stimulus
Unconditioned Stimulus (US): any stimulus ore event that occurs naturally, prior to learning.
Food placed in a dog’s mouth will trigger a response without any training being necessary.
The Unconditional Response
Unconditioned Response (UR): the response that occurs after the unconditioned stimulus. Occurs
naturally, prior to any learning.
The specific response that a US naturally triggers-> unconditional response. When a US occurs a UR
always follows without the need for any training. Classical Conditioning 1 & 2
The UR is often a biologically programmed reflex or natural response.
o The US of food elicits a UR of salivation in the dog’s mouth.
The Conditional Stimulus
Conditioned Stimulus (CS): Paired with the unconditioned stimulus to produce a learned contingency.
Is previously neutral stimulus that after becoming associated with a US, eventually comes to trigger a
response on its own.
Pavlov paired a CS of the sound of a metronome with the US of food placed in the dog’s mouth.
The CS typically appears before the US. It may take several trials of training which the CS and US are
paired before the CS alone can stimulate a response. When this is occurs the organism had learned a
contingent relationship between the two stimuli.
The Conditional Response
Conditioned Response (CR): The response that occurs once the contingency that occurs once the
contingency between the CS and US has been learned.
Initially, the CS was a neutral stimulus that did not elicit a specific response. Following pairing with the US,
the CS elicits a conditional response (CR).
In Pavlov’s experiment, the CR is the salivation of the dog.
US: a naturally occurring even that triggers a response without requiring learning.
CS: a neutral even that is paired with the UD to produce a learned contingency.
UR: a physiological response that naturally follows the US.
CR: a learned response that is associated with a formerly neutral event following learning.
Acquisition: the process by which a contingency between a CS and US is learned.
Pavlov characterized the process of acquisition the process of acquisition as following a negatively
Although acquisition typically takes several trials, there are special cases where just one trial is sufficient.
Rats have developed special learning mechanisms for food selection to help them survive. Rats are
constantly searching for food sources and can run the risk of consuming something poisonous.
As a rule, rats generally avoid unfamiliar foods, a trait known as dietary neophobia. When rats do try novel
foods, they will only consume it in small quantities. By doing this, rats are able to effectively pinpoint a
specific food again.
This process is made especially efficient by the fact that rats can learn the contingency between food and
sickness in a single trial.
In theory, as longs as the CS continues to be a reliable cue for the US, the contingency will be maintained.
Extinction: the loss of the CR when then C no longer predicts the US.
Involves presenting the CS alone (without the US) repeatedly over many trials. At first, the CS will elicit a
CR. But over several trials, the CS will elicit a CR that is weaker and weaker, until it finally disappears.
However, if extinction leads to new learning, the learning of an inhibitory response to the CS, this would
suggest that there exist two learned processes that sit side by side. The original learned response to the CS
and a new inhibitory learned response to the CS.
If this was the case, retraining between the CS and US would occur at a faster rate.
Spontaneous Recovery: a phenomenon that suggests that extinction involves a new inhibitory learned
Following an extinction procedure in which the CS is presented repeatedly in the absence of the US, the CR
gradually fades. Classical Conditioning 1 & 2
However, following a rest period, the CS is presented once more, and it once again causes a CR. This
suggests that original learned association between the CS and US is not unlearned. Rather, extinction
seems to promote a learned inhibitory response that competes with the original learned contingency.
Generalization and Discrimination
World War 2
Conditioning in the real world can be far more complex. For example, a signal CS may not be identical every
time it is presented. During the wartime bombing of London in WW2, people developed a conditional fear
response to the whistling sound made by the falling bombs.
This was the case, even though the particular whistling sounds were different from one bomb to another,
depending on the distance, type, and weather condition. Nonetheless, this variable CS came to reliably
produce a fear response.
Classical conditioning of learned responses to a variety o