PS261 Chapter Notes - Chapter 4: Estimation Theory, Free Base, Orienting Response
Chapter Four – Classical Conditioning: Mechanisms
PART ONE – Ch. 4.2: What Makes Effective Conditioned/Unconditioned Stimuli?
..a: Iitial Respose to “tiuli
- CS does not elicit the CR initially
o Does so after being associated with the US
- US is able to elicit the target response from onset without any special training
- Definitions were stated in terms of elicitation of the response to be conditioned
- Identifying potential CS and US requires comparing responses elicited by each stimulus before
conditioning
o Makes it relative
- Event may serve as a CS relative to one stimulus, and a US to another
..: Novelty (Newness) of Conditioned and Unconditioned Stimuli
- Important in classical conditioning
- The Latent Inhibition/Conditioned Stimulus Pre-Exposure Effect
o Latent Inhibition/CS Pre-Exposure Effect: if stimulus is highly familiar, will not be as
readily associated with the conditioned stimuli as novel stimuli
1. Subjects first given repeated presentations of the CS by itself
▪ Pre-Exposure Phase – comes before Pavlovian conditioning trials
2. The CS is paired with the US using conventional classical conditioning procedures
▪ Subjects slower to acquire responses because of CS pre-exposure
• Disrupts or inhibits learning
o Similar to habituation
▪ Both serve to limit the processing and attention to stimuli that is presented by
themselves, and therefore inconsequential
o Dominant interpretation is that CS pre-exposure reduces attention to the CS
▪ Disrupts subsequent learning about this stimulus
- The Unconditioned Stimulus Pre-Exposure Effect
o US Pre-Exposure Effect: experiments on the importance of the novelty (newness) of the
unconditioned stimulus
▪ Similar to CS pre-exposure experiments
o Involves 2 stages
1. Subjects are first given repeated exposure to the US by itself
2. Then paired with the US, and progress of learning is monitored
o Familiarity with the US before pairing with the CS slows down the response to the CS
more than novel CS–US pairings
..: Intensity and Salience of Conditioned and Unconditioned Stimuli
- Important for classical conditioning
o Most biological and physiological effects are related to the intensity of the stimulus input
- Stimulus intensity contributes to stimulus salience
o Can make stimulus more salient or significant by making it more intense and more
attention-grabbing
o Can also make it more relevant to biological needs of the organism
- Another way to increase salience of the CS is to make it more similar to the kinds of stimuli that
an animal is likely to encounter in its natural environment
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4.2.d: Releae of the Coditioed “tiulus for the Partiular Uoditioed “tiulus
- Another variable that governs the rate of classical conditioning is the extent to which the
conditioned stimulus is relevant to or belongs with the unconditioned stimulus
- Garcia and Koelling
o Compared learning about peripheral pain (shocks in feet) and learning about illness
(induced by irradiation or drug injection) in a study conducted on rats
o Likely to get sick after eating poisonous food, encounter peripheral pain after being
chased and attacked by a predator
▪ Conditioned Stimuli:
• Flavoured solution of water
• Audiovisual signal
o Rats drank from tube, then activated an audiovisual stimulus
▪ Either received a shock or were made sick
- Learning depends on the relevance of the CS and the US that was employed
o Taste was associated with illness
o Audiovisual was associated with shock
- Rapid learning only occurred if the CS was combined with the appropriate US
- Phenomenon reflects a genetic predisposition for the selective learning of certain combinations
of CS and US
- Stimulus-relevance effects are also prominent in the acquisition of fear in primates
o Fear conditioning is more rapid with fear-relevant cues than with fear-irrelevant cues
o Seems to reflect an evolutionary adaptation to detect dangerous stimuli and acquire a
fear to such cues
4.2.e: Learig Pheoea that Eted the Rage of Coditioed “tiuli
- If Pavlovian conditioning was only applicable to situations that involve a US, it would be limited
- Forms of Classical Conditioning without Unconditioned Stimulus
1. High-Order Conditioning:
▪ Irrational fears develop through this form
▪ Occurs in two phases
• Cue (CS1) is paired with a US often enough to condition a strong response
• CS1 paired with CS2 elicits the CR
▪ CS2 is conditioned with a US
▪ Conditioning operates at different levels
• Second-Order Conditioning: one conditioned CS (CS1) is paired with the
US, and the second CS (CS2) is paired with CS1 without the US
▪ Whether the first and second-order stimuli are presented simultaneously, or
one after another is another important variable
▪ With higher-order conditioning, classical conditioning can happen without a
primary US as long as there is a previously conditioned stimulus
2. Sensory Preconditioning:
▪ Associations can be learned between two stimuli, each eliciting only a mild-
orienting response before conditioning
▪ Two-stage process
• Association between CS1 and CS2 is established during the sensory
preconditioning phase – no association to the US
• CS1 or CS2 is linked to an aversive or appealing stimulus
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o Response of the other CS to the US reflects whether the pairing
has been made
▪ Helps make sense of things we like or dislike for no apparent reason
PART TWO – Ch. 4.3: What Deteries the Nature of the Coditioed Respose?
- The Stimulus-Substitution Model
o Most enduring explanation for the nature of the conditioned response
o The association of the CS with the US turns the CS into a surrogate US
▪ The CS has the same functions as the US
o New connection develops between the circuits activated by the CS and the circuits
previously active only by the US
▪ Presentation of the CS activates the same response as the US
..a: The Uoditioed “tiulus as a Deteriig Fator for the Coditioed Respose
- Different Unconditioned Stimuli elicit different Unconditioned Responses
o If conditioning turns the CS into a surrogate US, the CS conditioned with a different US
should elicit different types of CRs
- Jenkins and Moore (1973):
o Compared Pavlovian conditioning in pigeons with food vs. water as the Unconditioned
Stimuli:
▪ Pigeons change beak opening size based on the size of the grain
▪ Lower mostly-closed beak to drink water
o Unconditioned Responses: drinking and eating
▪ Differ in both speed and form
o Conditioned Stimulus: illumination of a pecking key for 8 seconds
▪ Paired with the presentation of a grain or access to water
• Grain – pecks were rapid with beak open at moment of contact
• Water – pecking was slower with beak closed
o Conditioned Response: similar to the form of the UR
- Learning and Homeostasis: Special Case of Stimulus Substitution
o Homeostasis: introduced by Canon to refer to physiological mechanisms that serve to
maintain the stability of critical physiological functions
▪ Achieving homeostasis requires the challenge to homeostatic level to trigger the
compensatory reaction that will neutralize the disturbance
▪ Ex. lowering of body temperature in warm-blooded animals
• Reactions include:
o Peripheral vasoconstriction and shivering
o Operates through negative feedback loop
▪ Homeostatic mechanisms are conceived to operate similar to the thermostat
o Pavlovian conditioning provides the means for such feed-forward anticipation
▪ The conditioned response to a physiological challenge is the same as the
reflexive compensatory response to a challenge
• The conditioned response is the same as the unconditioned response,
but the unconditioned response is a compensatory reaction to a
physiological disturbance
o Conditioned homeostatic responses are examined most extensively in studies of how
organisms respond to the administration of a psychoactive drug
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