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Chapter 4

Chapter 4 - Classical Conditioning - Mechanisms.docx

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PSYC 2330
Francesco Leri

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Classical Conditioning: Mechanisms What Makes Effective Conditioned and Unconditioned Stimuli? Initial Responses to the Stimuli  To identify the potential CSs and USs you have to look at the responses elicited before conditioning – what it can be used for is relative to the other stimuli in the situation Novelty of Conditioned and Unconditioned Stimuli  Learning is faster if the CS and US are novel, rather than highly familiar. This is called the latent-inhibition effect or CS-preexposure effect. It inhibits or disrupts learning and evidence for this has been found in rats and humans. If this occurs, the CS will not be associated as quickly to the US. Very similar to habituation because both limit processing and attention. o Latent inhibition involves attention and has been implicated in diseases which include deficits in attention – schizophrenia o Latent inhibition is reduced by dopamine receptor agonists (increase release) and enhanced by dopamine receptor antagonists (decrease release of dopamine) o The same thing is the US-preexposure effect which simply states that if the US is highly familiar the subject will develop conditioned responses slower  There is an associative interference mechanism that has been emphasized during analyses – this means that when you are preexposing a subject to the US certain cues may exist that are associated with the US – these cues may then become CSs and may interfere with learning when you begin the subsequent conditioning phase CS and US Intensity and Salience  The more intense the CS and US are the more vigorous the conditioned responding is – learning will occur more rapidly with more salient stimuli (significant or noticeable) – this can be through intensity or by making it more relevant to the biological needs of an organism, also make it more similar to stimuli seen in an animals natural environment. This doesn’t also mean that learning is rapid but also that more aspects of the behaviour become conditioned and learning is not disrupted as easily by increasing the CS-US interval CS-US Relevance, or Belongingness  Extent to which the CS is relevant or belongs with the US  Study involving rats suggested that rats conditioned with sickness learned a stronger aversion to taste than to audiovisual cues, rats conditioned with shock learned a stronger aversion to audiovisual than to taste cues  Studies with cocaine as well have shown some results which indicate 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 Learning Without an Unconditioned Stimulus  Can occur – two different forms of classical conditioning without a US – higher-order conditioning and sensory preconditioning Higher-order conditioning  How irrational fears often develop  Ex. a lady who develops a fear of crowds (CS) because she was shoved in a crowd (US) because of that she avoided crowds and only went to movies (CS2) during day, one day a crowd came in of students and she was scared (CR) The crowd is the CS1 and the US is being shoved and in the second phase, the crowd exists in the movie theatre but being shoved doesn’t. The CS2 is the movie theatre and can be elicited  Conditioning can operate at different levels as shown by this example – the crowd condition with the shoving is first-order conditioning while the second condition with the movie theatre is second-order conditioning  First-order conditioning CS1 is paired with the US, second-order conditioning the CS1 is paired with the CS2 o Third-order would be CS2 used to condition another stimulus CS3  Number of non-US trials is a factor influencing which conditioning will occur – conditioned inhibition or excitatory second-order conditioning – with few nonreinforced trials, second-order excitatory conditioning will occur o Simultaneous first- and second-order stimuli will develop conditioned inhibition  Very little research CS3 and CS4, etc. but CS2 exists so opens a lot of doors on how we can condition – only requires that the first CS1 be present Sensory Preconditioning  Ex. you associate cinnamon (CS1) and vanilla (CS2) with one another because they are always in desserts, then you get food poisoning (US) off of something containing cinnamon (CS1) and you develop an aversion (CR) to cinnamon but also to vanilla even though the vanilla is not what made you sick  Two-stage process – first is the association between CS1 and CS2 without the US, this association is not usually evident in any behavioural responses because neither has been paired with a US – second stage involves the pairing of CS1 with the aversive US (illness) and a CR (conditioned aversion) develops to CS1 – then when tested with CS2 there will be an aversion  Important because CS2 was never paired with the US What Determines the Nature of the Conditioned Response? The Stimulus-Substitution Model  In this model it is assumed that the CS becomes a substitute for the US and it functions like the US did previously – it is assumed to activate neural circuits previously activated only by the US and elicits responses similar to the US CS pathway US pathway Response Pathway  The solid arrow indicates preexisting neural connections and the dashed arrow indicates neural connections established by conditioning – because of this, the CS comes to elicit responses previously elicited by the US The US as a Determining Factor for the CR  If this is the case, CSs conditioned with different USs should elicit different types of responses  The nature of conditioned response depends on the US  Pigeons drink and eat differently, when they eat they open their mouth and peck rapidly but when they drink then close their beak and lower it into the water and periodically suck o Looked at the different CR to different USs o The CS was illumination of a pecking key for 8 seconds and was paired with either food or water (US) o When food was US the pigeons pecked at the key light as if eating – rapid and beaks open at the moment of contact o When water was the US the CR was pecking movements but slower and was made with the beak closed and swallowing often occurred o The form of the CR often resembled the form of the UR Learning and Homeostasis: A Special Case of Stimulus Substitution  Negative feedback loop – our bodies system for maintaining internal temperature – drop in body temp we engage in reactions to increase it  We are able to anticipate signals that indicate we will get cold and make adjustments in advance to avoid a drop in body temperature – feed forward compensatory adjustments o In this case the CR is the same as the UR but the UR is a compensatory reaction to the physiological disturbance  Conditioned homeostatic responses are extensively studied in how organisms respond to administration of a psychoactive drug o Drugs often cause physiological challenges to homeostasis which trigger unconditioned compensatory responses (UR) – cues that become associated with those challenges can come to activate the compensatory reactions as anticipatory or feed-forward conditioned responses o Administration of a drug is a conditioning trial where the cues related to the administration are paired with the effects of the drugs  Caffeine can be paired with the smell and taste of coffee and those cues can be predictive of the physiological effects of caffeine  Experiment which looked at cocaine users who had never used heroine and used a control group who had never used either – when cocaine cues were presented (buying cocaine, going through the motions of smoking it, listening to experiences about using it) the group who had used cocaine before showed elevated heart rates but they did not show any changes in heart rate when heroine cues were presented. The control group did not show elevations in heart rate in any of the test o The increased heart rate was specific to the cocaine-related stimuli o People with a history of cocaine use reported feelings of craving and withdrawal  Drug related cues activated emotions opposite to the direct effects of cocaine  Environmental cues conditioned by psychoactive drugs can elicit craving emotions related to the drug US – those anticipatory CRs can also be elicited by the initial effects of a drug experience o For drug addicts, the beginning of a buzz or high are typically followed by a substantial additional drug intake and a more intense high o Therefore, the initial small buzz can serve as a CS signaling increased drug intake and can elicit cravings and other drug conditioned reactions o The CS is an internal sensation or introceptive cue o This is why it is hard for drug addicts to use in moderation – the conditioned craving that begins when you use a tiny bit The Conditioning Model of Drug Tolerance  Evidence that tolerance can develop from Pavlovian conditioning of homeostatic compensatory processes, not only pharmacological processes  Assumes that each time you take the drug it is a conditioning trial and uses the idea of learned homeostasis o When you take the drug there are physical changes which disrupt your homeostasis, those changes in turn trigger UR to counteract the disturbance o Through conditioning, stimuli that accompany the drug administration become conditioned to elicit these compensatory adjustments – things around when you do the drug begin to elicit the responses that drugs do (lower body temp, etc.) o The conditioned responses counteract the drug effects so the impact of the drug is reduced  Overdosing can occur when you do drugs in an unfamiliar environment because the cues that counteract the drug effects are missing  Key prediction of this model is that drug tolerance will be reduced if participants receive the drug under novel circumstances or in the absence of the usual drug-predictive cues  Also, various factors (ex. CS preexposure) that amplify the development of conditioned responding will also amplify the development 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, not o
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