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Chapter 4

PSYC 2330 Chapter Notes - Chapter 4: Classical Conditioning, Conditioned Taste Aversion, Latent Inhibition

Course Code
PSYC 2330
Francesco Leri

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Ch. 4: Classical Coditioig
What Makes Effective Conditioned and Unconditioned Stimuli?
Initial Responses to Stimuli
According to Pavlov, the CS does not elicit the conditioned response initially but
comes to do so as a result of becoming associated with the US. By contrast, the US is
effective in eliciting the target response from the outset (without
Therefore, identifying potential CSs and USs requires comparing the responses
elicited by each stimulus.
Novelty of Conditioned and Unconditioned Stimuli
In studies of habituation, we can see that the behavioural impact of a stimulus
depends on its novelty. In classical conditioning, if either the CS or the US is highly
familiar, learning occurs more slowly compared to when the CS and US are novel.
latent-inhibition effect: (or CS-preexposure effect) interference with conditioning
produced by repeated exposures to the CS before the conditioning trials
Latent inhibition is similar to habituation. Both phenomena serve to limit processing
and attention to stimuli that are presented without a US and are therefore
US-preexposure effect: interference with conditioning produced by repeated
exposures to the US before conditioning trials
CS and US Intensity and Salience
More vigorous conditioned responding occurs when more intense conditioned and
unconditioned stimuli are used.
Stimulus intensity is one factor that contributes to what is generally called stimulus
stimulus salience: the significance or noticeability of a stimulus. Generally,
conditioning proceeds more rapidly with more salient (i.e. noticeable) conditioned
and unconditioned stimuli
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One can make a stimulus more salient by making it more attention getting, making it
more relevant to the biological needs of the organism, or by making it more similar
to the kinds of stimuli the organism is likely to encounter in the natural
CS-US Relevance, or Belongingness
Another variable that governs the rate of classical conditioning is the extent to
which the CS is relevant to or belongs with the US.
- First demonstrated in an experiment by Garcia and Koelling (1966)
- Learning depends on the relevance of the CS to the US
- Relevance of the CS to the US causes rapid learning to occur
Stimulus-relevance effects are also prominent in the acquisition of fear in primates.
However, the difference is not observed when an appetitive US is used.
Learning Without an Unconditioned Stimulus
There are 2 forms of classical conditioning without a US: higher-order conditioning
and sensory preconditioning.
higher-order conditioning: a procedure in which a previously conditioned
stimulus () is used to condition a new stimulus ()
- Irrational fears are often learned through higher-order conditioning
- Occurs in two phases
Phase 1: A cue () is paired with a US often enough to condition a strong response
to .
Phase 2: The  is then paired with a new stimulus ()
The term higher order conditioning implies that conditioning may be considered
to operate at different levels.
- Pairing a  with a US is first-order conditioning
- Pairing a  with a  is second-order conditioning
- Using a  to condition another stimulus (, than that is third-order
Advertising campaigns also make use of higher-order conditioning. When a new
product () is paired with something we have already learned to like (), we
are more likely to buy the product.
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sensory preconditioning: a procedure in which a biologically weak stimulus ()
is repeatedly paired with another biologically weak stimulus (). Then,  is
conditioned with an unconditioned stimulus. In a later test trial,  will also elicit
the conditioned response, even though  was never paired with the US.
ex. You usually encounter both of the flavours of vanilla and cinnamon together in
pastries. If you somehow acquire a taste aversion to vanilla, then it will likely come
with a taste aversion to cinnamon as well.
Sensory preconditioning and higher order conditioning help us to understand why
we seem to like or dislike things for no apparent reason (i.e. these stimuli were not
directly associated with a positive or negative US.
What Determines the Nature of the Conditioned Response?
Classical conditioning is usually identified by the development of a new response to
the conditioned stimulus. Why does one set of responses become conditioned in one
situation but the other responses develop to the CS in other circumstances?
The US as a Determining Factor for the CR
The most obvious factor that determines the nature of the conditioned response is
the unconditioned stimulus that is used. Interestingly, even small variations in the
nature of the US can produce changes in the nature of the CR.
- ex. experiment with Jenkins and Moore (1973) with pigeons
The fact that the form of the conditioned response is determined by the US
encouraged Pavlov to propose the stimulus substitution model.
stimulus substitution: the theoretical idea that as a result of classical conditioning
participants come to respond to the CS in much the same way that they respond to
the US.
According to this model, the association of a CS with a US turns the CS into a
surrogate US. Thus, the CS is assumed to activate neural circuits previously
activated only by the US and elicits responses similar to those elicited by the US.
This model correctly emphasizes that the nature of the CR depends a great deal on
the US that is used in a conditioning procedure. However, in many cases the CR does
not resemble the UR.
- ex. Foot shock causes rats to leap into the air, but the conditioned response to a
tone paired with a foot shock is freezing and immobility.
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