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Lecture

PSYCH 1X03 Lecture Notes - Systematic Desensitization, Drug Tolerance, Bradypnea


Department
Psychology
Course Code
PSYCH 1X03
Professor
Joe Kim

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Psychology Lecture 4/5: Classical Conditioning
Bernard Ho
September 25, 2010
Orienting Responses, Habituation and Sensitization
Orienting responses are important for focusing your attention to evaluate unfamiliar
stimuli which may potentially signal danger or unexpected opportunity
However, if you responded equally to every stimuli in the environment, you would
become overwhelmed and your divided attention may cause you to miss out on critical
information
Habituation
o A simple form of learning shown by a decrease in response to a stimuli or event
as it becomes familiar
o Functions to limit an orienting response and to ignore inputs that have become
familiar and found to be inconsequential
o In some situations, the opposite effect to habituation is just as important
o Two processes can lead to an increase in responsiveness to a stimulus or event
o Dishabituation is an increase in responding that follows a change in the
stimulus that has become familiar
Is important because a change in stimulation of a familiar stimulus can
indicate important information
The other process is sensitization
o Increase in response to repeated presentation
o Can be an adaptive behaviour because it prompts you to engage in behaviours
appropriate to escaping a potentially harmful stimulus
Key difference between the two processes is that dishabituation involves the recovery
of the original response, while sensitization produces a response stronger than the
original one
Whether a particular stimulus leads to habituation or sensitization depends on factors
such as intensity of the stimulus
o More intense stimulus tend to lead to sensitization and modestly intense stimuli
tend to lead to habituation
Learning
Refers to a relatively enduring change in an organism’s behaviour, capabilities or
knowledge due to experience
Two types
o Classical conditioning
Allows us to associate two related events
The learning of a contingency between a particular signal and a later
event that are paired in time/space
Cue (signal) + event reaction
Cue (signal) reaction
Ivan Pavlov

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Sound of a metronome signalled to a dog that food was about to
be delivered
Prior to training, sound of metronome had no observable effect
on dog’s behaviour
After training, a dog would begin to salivate in response to sound
of metronome alone
New behaviour was called conditional reflex
Pavlov was technically studying a contigent relationship,
presentation of one stimulus reliably leads to the presentation of
another
Ex. Flash of lightning before crash of thunder
When an organism learns the association between a signal and an event,
a contingency has formed between the two stimuli
Learning these contingencies is the essence of classical conditioning
Conditional response can promote survival
o Instrumental conditioning
Allows us to associate actions and consequences
Terminology
Unconditional stimulus
o One that unconditionally, naturally and automatically triggers a response in the
absence of learning
o Food placed in dog’s mouth
Unconditional response
o Specific response that unconditional stimulus naturally triggers
o Biologically determined reflex that is elicited in the absence of prior learning
o When US occurs, UR always follows without any need for training
o Salivation after food placed in dog’s mouth
Conditional stimulus
o Previously neutral stimulus, that after becoming associated with the US,
eventually triggers a response of its own
o Sound of metronome with food placed in dog’s mouth
o Typically appears before the US
Conditional response
o Following pairing with US, CS elicits a conditioned response
o Often CR is very much like UR
o CS of sound of metronome will eventually elicit a CR of salivation
Acquisition
o Process by which a contingency between a CS and US is learned
o Pavlov characterized the process of acquisition as following a negatively
accelerating curve
o Most learning happens in early trials
o During each additional trial, there is some learning, but never as much as in the
earlier trials
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o Taste aversion
Ex. When rats eat something bad for them, they won’t eat anything else
similar to it
Atypical because happens after one trial
Extinction
Lasting effects
o In theory, as long as the CS continues to be a reliable cue for the US,
contingency will be maintained
o However, if conditions change such that the CS is no longer a reliable cue for the
US, the CR will eventually fade
Extinction is the process in which a CR can be made to fade
o Involves presenting the CS alone (without US) repeatedly over many trials
o At first, CS will elicit the CR, but eventually CR will become weaker and weaker,
until it fades
Learning perspective
o Two hypotheses
Is previous contingency unlearned?
If so, retraining between CS and US would lead to acquisition of
the CR at same rate as original training
Old learned contingency remains and competes with new inhibitory
response that is learned to the CS?
If so, retraining between CS and US would occur at a faster rate
compared to original training
Spontaneous recovery
o Suggests that extinction involves a new inhibitory learned response
o Following an extinction period in which CS is presented repeatedly in absence of
US, CR gradually fades
o However, following a rest period, the CS is presented again and it elicits the CR
o Suggests that extinction seems to promote a learned inhibitory response that
competes with original learned contingency
o One possible explanation is the phenomenon of renewal
If a response is extinguished in a different environment than where it
was acquired, the fully expressed CR is observed if the animal is returned
to the environment in which acquisition took place
Furthermore, reconditioning proceeds faster than initial acquisition
o In other words, relearning is faster than the original rate of learning
o Even following extinction in which the CR is no longer observed the subject still
retains some memory of the learning
Higher Order Conditioning
In higher order conditioning, the established CS is now paired with a new stimulus,
creating another CS capable of eliciting a CR
Typically, the CR elicited in HOC is weaker and more vulnerable to extinction compared
to the original CR
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