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Chapter 4

Chapter 4 - Classical Conditioning Mechanisms.docx

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University of Guelph
PSYC 2330
Francesco Leri

Chapter 4 Classical Conditioning: Mechanisms What Makes Effective Conditioned and Unconditioned Stimuli? Initial Responses to the Stimuli - According to Pavlov’s definitions 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 any special training. - Because of this, identifying potential CSs and USs requires comparing the responses elicited by each stimulus before conditioning. o I.e. Saccharin solution serves as the CS in a taste aversion experiment and can also serve as the US in a sign tracking experiment. o Therefore whether the saccharin solution serves as the CS or US is dependent on its relation to other stimuli in the situation. Novelty of Conditioned and Unconditioned Stimuli - Novelty is very important in classical conditioning, b/c if either the conditioned or the unconditioned stimulus is highly familiar, learning proceeds more slowly than if the CS and US are novel. Latent Inhibition or CS Preexposure - The latent inhibition effect, also known as the CS-preeexposure effect, is when a stimulus is highly familiar and wont be as readily associated with a US as a novel stimulus. - They involve two phases: o First subjects are given repeated presentations of the CS by itself.  This makes the CS highly familiar and of no particular significance. o After, the CS is paired with the US using conventional classical conditioning procedures. o Results are that the subjects are slower to acquire responding b/c of the preexposure. - Latent inhibition is very similar to habituation b/c they both serve to limit processing and attention to stimuli that are presented by themselves and are therefore inconsequential. The US Preexposure Effect - Subjects are first given repeated exposures to the US presented by itself. - The US is then paired with a CS, and the progress of learning is monitored. - Subjects familiarized with a US before its pairings with a CS are slower to develop conditioned responding to the CS. This is known as the US- Preexposure effect. 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 more generally called stimulus salience (roughly corresponds to significance or noticeability). o Learning will occur more rapidly if the stimuli are more salient. o One can make stimuli more salient by making it more intense (more attention getting) and also more relevantto the biological needs of the organism. o i.e. sodium deficient rats learn stronger aversions to the taste of salt than nondeficient control subjects. o Another way to increase the 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. CS-US Relevance, or Belongingness - In their environment rats are likely to get sick by eating poisonous food, and they are likely to encounter peripheral pain after being chased and bitten by a predator that they can hear and see. o I.e. the experiment showed that learning would occur most rapidly if taste (CS) and sickness (US) were paired together, and audiovisual (CS) and shock (US) were paired together. o This is b/c they have relevance to each other. - Results also indicate that visual cues are relevant to learning about biologically significant positive or pleasant events and auditory cues are relevant to learning about negative or aversive events. - Fear conditioning occurs most rapidly in situations that provide recurrent survival threats in mammalian evolution. Learning Without a Unconditioned Stimulus - There are two different forms of classical conditioning without a US: Higher-Order Conditioning - Higher-Order conditioning is a procedure in which a previously conditioned stimulus (CS1) is used to condition a new stimulus (CS2). o Irrational fears develop through higher-order conditioning. o i.e. Lady initially developed fear for crowds. Being in a crowd was the CS that elicited conditioned fear. One time she was at a movie theater and it began to become packed with people. She then started to associate cues of the movie theater with crowds. The CS (crowds) had conditioned fear to another (movie theater) that previously elicited no fear. - 1 phase: a cue (CS1) is paired with a US often enough to condition a strong response to CS1. nd - 2 phase: once CS1 elicited the conditioned response, pairing CS1 with a new stimulus CS2 (cues of the movie theater) was able to condition CS2 to also elicit the conditioned response. Sensory Preconditioning - Associations can also be learned b/w two stimuli, each of which elicits only a mild orienting response before conditioning. - The two flavors cinnamon and vanilla are often encountered together in pastries without ill effects. This creates an association b/w the two. - If you then acquired an aversion to cinnamon through food poisoning or illness, then chances are you will acquire aversion to vanilla as well. o This is an example of sensory preconditioning. - 1 phase: CS1 and CS2 become associated with one another when there is no US. nd - 2 phase: the cinnamon flavor (CS1) is paired with illness (US) and a conditioned aversion (the CR) develops to the CS1. o The subjects are then tested with CS2, which they now show aversion to. What Determines the Nature of the Conditioned Response? The Stimulus-Substitution Model - According to this model, the association of the CS with the US turns the conditioned stimulus into a surrogate US. (The conditioned stimulus comes to function much like the US did previously.) o Thus the CS is assumed to activate neural circuits previously activated only by the US and elicit responses similar to the US. The US as a Determining Factor for the CR - The form of the conditioned response resembles the form of the UR. - See page 113 for more. Learning and Homeostasis: A Special Case of Stimulus Substitution - The concept of homeostasis was introduced by Walter Cannon to refer to physiological mechanisms that serve to maintain the stability if critical physiological functions. o Achieving homeostasis requires that a challenge to the homeostatic level trigger a compensatory reaction that will neutralize the disturbance. o For more see page 115 and 116. The Conditioning Model of Drug Tolerance - Drug Tolerance is said to develop when repeated administrations of the drug have progressively less effect. o B/c of this, increasing doses are required to produce the same drug effect. o There is substantial evidence that drug tolerance can result from Pavlovian conditioning of homeostatic compensatory processes. - This model assumes that each drug-taking episode is a conditioning trial and is built on the idea of learned homeostasis. o The administration of a psychoactive drug causes physiological changes that disrupt homeostasis. o Those physiological changes in turn trigger unconditioned compensatory adjustments to counteract the disturbance. o Through conditioning, stimuli that accompany the drug administration become conditioned to elicit these compensatory adjustments. o B/c the conditioned responses counteract the drug effects, the impact of the drug is reduced, resulting in the phenomenon of drug tolerance. The CS as a Determinant of the Form of the CR - The form of the CR is also influenced by the nature of the CS. - See more page 118-119. Conditioned Responding and Behavior Systems - The understanding of conditioned behavior will ultimately require knowledge of the normal functions of behavior systems engaged by the various CSs, the natural, unlearned organization within those systems, and the ontogeny of those systems. - Behavior systems theory assumes that the presentation of a US in a Pavlovian conditioning procedure activates the behavior system relevant to that US. o I.e. Food-unconditioned stimuli activate the foraging and feeding system. - As a conditioned stimulus becomes associated with the US, it becomes integrated into the behavioral system and comes to elicit component responses of that system. o Thus, food conditioned stimuli come to elicit components of the feeding system and the sexual conditioned stimuli come to elicit components of the sexual behavioral system. - I.e. in experiments, effects of the CS-US interval on the conditioning of focal search and general search responses in male domesticated quail. When the CS-US interval was one minute, conditioning resulted in increased focal search behavior. When the CS-US interval was 20 minutes, conditioning resulted in increased general search behavior. S-R vs. S-S Learning - Two or
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