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Chapter 9

Principles of Learning-Chapter 9.docx

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Department
Psychology
Course Code
PSYC 2330
Professor
Francesco Leri

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Principles of Learning: Chapter 9- Extinction of Conditioned Behaviour (p. 300)  Extinction can only be conducted after a response or association has been established using Pavlovian or instrumental conditioning  Often the goal is to reverse the effects of acquisition  True reversal of acquisition is rare/may not be possible  Extinction does not erase what was originally learned  Extinction involves new learning of an inhibitory S-R association  Inhibition arises from the frustrative effects of the unexpected absence of reward  Intermittent or partial reinforcement permits organisms to learn about non-reward in ways that serve to immunize them against the effects of extinction  In pavlovian conditioning: the outcome or unconditioned stimulus is presented as a consequence of a conditioned stimulus  In instrumental conditioning: the reinforcing outcome is presented as a consequence of the instrumental response  Extinction: involves omitting the US, or reinforce.  In classical conditioning: extinction involves repeated presentations of the CS by itself  In instrumental conditioning: extinction involves no longer presenting the reinforce as a consequence of the instrumental response  Extinction is often viewed as the reserve/opposite of acquisition: Rescorla-Wagner Model: however, this is incorrect  Extinction: an active process produced by the unexpected absence of the US or the reinforce  Forgetting: a decline in responding that may occur simply because of the passage of time  Extinction is studied through: brain structures, neurotransmitter systems, cellular and genetic mechanisms.  Social phobia, fear of flying, claustrophobia and other pathological fears and phobias are typically treated with some form of an exposure therapy: extinction procedure in which participants are exposed to cues that elicit fear in the absence of the aversive US.  Exposure to the actual fearful stimulus is the best way to conduct exposure therapy; often not practical though.  Having them imagine the fearful situation helps; more vivid/realistic exposure is possible with virtual reality techniques.  Exposure therapy also for drug addiction; aim to extinguish cues association with the drug taking behaviour Effects of Extinction Procedures  The most obvious behavioural effect is that the target response decreases when the response no longer results in reinforcement  Rat experiment: experimental chamber had two response levers on one wall and a round response key on the opposite wall  During reinforcement phase: rat has to make 3 responses in a row to obtain a food pellet (could press left lever 3 times, each lever and response key once, etc.)  After responding was established by the reinforcement contingencies in both groups, the rats were shifted to an extinction procedure in which food was no longer provided no matter what they did  Subjects reinforced for varying their responses showed much more variability than the subjects that did not have to vary their behaviour.  The second group responded somewhat faster, maybe because they didn’t have to move from various levers, and the response key to change the sequence of presses  Extinction produced a decline in the rate of responding in both groups  The increase in response variability was evident during the 1 extinction phase and increased in further sessions  Therefore, extinction produced a decline in the number of response sequences the subjects completed but it increased the variability of the sequences  Extinction procedures also often produce strong emotional effects  When you are used to receiving reinforcement it gets taken away leads to withdrawal of the expected reinforce creates frustration  Frustrative non-reward energizes behaviour  Frustration may sometimes lead to aggression  Example of frustrative aggression:2 animals/pigeons)placed in the same skinner box;  ^ when one animal is reinforced for pecking a key, other animal is restrained  As long as the 1 is reinforced it’s fine, when reinforcement stops, pigeon will attack the innocent restrained bird  Extinction induced aggression has been seen in studies with; pigeons, rats, and people Consolidation: the process of forming a long term memory  Consolidation depends on protein synthesis  If given a drug that inhibits protein synthesis (eg. Anisomycin), don’t remember fear conditioning  Administration of anisomycin soon after training disrupts the memory of conditioning while delayed drug treatment has little effect  Subjects that undergo extinction treatment in the presence of a protein synthesis inhibitor later exhibit a robust CD, as if the extinction treatment had not occurred Renewal: a recovery of acquisition performance when the contextual cues that were present during extinction are changed.  The change can be a return to the context of original acquisition or a shirt to a neutral context  Demonstrated in a classic study by Bouton and King (1983)  Studied the acquisition and extinction of conditioned fear in lab rats  Rats were 1 conditioned to press a response lever for good reinforcement  Acquisition of fear was then accomplished by pairing a tone CS with foot shock  Fear conditioning occurred in one of two experimental chambers that provided distinctively different contextual cues  Context used for training was counterbalanced across subjects and designated as context A  The tone-shock pairings resulted in a conditioned suppression of lever pressing during presentation of the tone  Subjects were then assigned to 1 of 3 groups for the extinction phase of the experiment  2 of the groups received 20 extinction trails; presentation of the tone CS without shock  Group A: extinction trials occurred in the same c
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