PSYC 2330 Chapter 4: Classical Conditioning: Mechanisms

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12 Oct 2017
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Ch. 4 Classical Conditioning Mechanisms
What makes effective conditioned and unconditioned stimuli?
Initial responses to the stimuli
- CS does not elicit the conditioned response initially but comes to do so as a result of
becoming associated with the US
- US is effective in eliciting the target response from the outset (unconditionally)
without any special training
- Identifying potential CSs and USs requires comparing the responses elicited by each
stimulus before conditioning
o Such a comparison makes the identification of CSs and USs relative
o A particular event may serve as a CS relative to one stimulus and as a US
relative to another
o Ex. ex. food pellets flavoured with sucrose
Taste of the pellets may serve as a CS in a taste-aversion
conditioning procedure, in which conditioning trials consist of
pairing the sucrose pellets with illness
Participant will acquire an aversion to eating the sucrose pellets
o Ex. using food pellets as a US
Conditioning trials involved inserting a response level (the CS)
before each delivery of the sucrose pellet (the US)
Eventually the rats began to approach and press the response lever
o Shows that sucrose pellets can be either a US or a CS
Novelty of conditioned and unconditioned stimuli
- highly familiar stimuli elicit less vigorous reactions than do novel stimuli
- if either the conditioned or the unconditioned stimulus is highly familiar, learning
occurs more slowly than if the CS and US are novel
The latent-inhibition or CS-preexposure effect
- the idea that if a stimulus is highly familiar, it will not be as effective as a CS than if it
were novel
o participants are given repeated presentations of the CS by itself (the
preexposure phase) which disrupts learning
o appear to protect the organism from information overload by attenuating
the processing of previously irrelevant stimuli – Lubow
- a major symptom of schizophrenia is the inability to suppress attention to irrelevant
stimuli, and individuals with it show a disruption of the latent-inhibition effect
o latent inhibition and schizophrenia share some of the same dopaminergic
neurobiological mechanisms
The US-preexposure effect
- ex. rats first received 80 presentations of one of two types of flavoured food pellets
on each of 5 days, for a total of 400 US preexposure trials
o pellets were delivered into food cup between two retractable levers
o 20 pavlovian conditioning trials were then conducted
o at the start one of the response levers was inserted into the chamber for 10
seconds, followed by a bacon pellet
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o on other trials, the level was presented paired with a chocolate pellet
o conditioning proceeded faster for the lever paired with the novel food than
for the level paired with the familiar food
o figure 4.1
CS and US intensity and salience
- intensity of conditioned and unconditioned stimuli is another important variable
- more vigorous conditioned responding occurs when more intense conditioned and
unconditioned stimuli are used
- salience roughly corresponds to significance or noticeability
- theories of learning typically assume that learning will occur more rapidly with
more salient stimuli
- more salient = more intense stimuli
- more salient = more relevant to the biological needs of the organism
o ex. animals become more attentive to the taste of salt if they suffer a
nutritional salt deficiency
- another way to increase salience of a CS is to make it more similar to the kinds of
stimuli an animal is likely to encounter in its natural environment
o if a naturalistic CS is used in sexual conditioning, the learning proceeds more
rapidly, more components of sexual behavior become conditioned, and the
learning is not as easily disrupted by increasing the CS-US interval
CS-US relevance, or belongingness
- extent to which CS is relevant to or belongs with the US also governs the rate of
classical conditioning
o ex. rats drank some flavoured water at the same time an audiovisual
stimulus was activated (CSs)
they then received a brief shock through the grid floor or were made
sick
rats were expected to learn an aversion of some kind
animals conditioned with shock subsequently suppressed their
drinking much more when tested with the audiovisual stimulus than
when tested with the taste CS
opposite result occurred for animals that had been conditioned with
sickness (they suppressed their drinking much more when the taste
CS was presented than when drinking produced the audiovisual
stimulus)
o showed that learning depended on the relevance of the CS to the US
o taste became associated with illness, and audiovisual cues became
associated with pain
o rapid learning only occurred if the CS was combined with the appropriate US
o figure 4.4
- extensive experience with tastes and sickness is not necessary for the stimulus-
relevance effect
o occurred in rats one day after birth
- fear conditioning progresses more rapidly with fear-relevant cues (the sight of a
snake) than with fear-irrelevant cues (sight of a flower)
o this doesn’t occur for appetitive US though
o seems there is an evolutionary adaptation to rapidly detect biologically
dangerous stimuli and acquire fear to such cues
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Learning without an unconditioned stimulus
- two different forms: higher-order conditioning and sensory preconditioning
- higher-order conditioning irrational fears are often learned through higher-
order conditioning
o ex. for someone who is afraid of crowds, them being in a crowd is a CS that
elicited conditioned fear
o how this fear was originally learned is unknown
o ex. lady goes to movie theatre in the middle of the day because she thinks
it’ll be dead but this one day there are a bunch of students there
she then associated the movie theatre with crowds
one CS (crowds) had conditioned fear to another (the movie theatre)
that previously elicited no fear
so this fear is irrational
o two phases:
first phase, CS1 is paired with a US often enough to condition a
strong response to CS1
once CS1 elicited the conditioned response, pairing CS1 with a new
stimulus CS2 was able to condition CS2 to also elicit the conditioned
response
the conditioning of CS2 occurred in the absence of the US
figure 4.5
o money is a powerful CS1 for human behavior. A child may become fond of
his or her uncle (CS2) if the uncle gives the child some money on each visit
(this is second-order conditioning)
o advertising campaigns also make use of higher-order conditioning
a new product (CS2) is paired with something we have already
learned to like (CS1) to create a preference for the new product
- sensory preconditioning associations learned between two stimuli
o ex. if you have a lot of desserts with vanilla and cinnamon in them, you
would probably associate them with each other. But what would happen if
you then acquired an aversion to cinnamon through food poisoning or
illness? You would probably reject the taste of vanilla as well as cinnamon
because of your prior association
o sensory preconditioning also involves a two-stage process
cinnamon and vanilla become associated with one another in the
first phase when there is no illness or US
this association is usually not evident in any behavioural responses
because neither CS has been paired with a US yet
during the second phase, cinnamon (CS1) is paired with illness (US)
and a conditioned aversion (CR) develops to CS1 (this is first-order
conditioning)
participants are then tested with CS2 and now show an aversion to
CS2 for the first time
the response to CS2 is noteworthy because CS2 was never directly
paired with a US
- these two types help us make sense of things we seem to like or dislike for no
apparent reason
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