PSY100H1 Lecture Notes - Classical Conditioning, Nucleus Accumbens, Habituation

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26 Mar 2012
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Chapter 6 – Learning and Reward
Learning
-an enduring change in behavior that results from experience
-is the result of many unique mechanisms that solve individual adaptive problems, not of general
learning mechanisms
oE.g. lungs breathe, ears hear. No general “sensing organ
-Conditioning: environmental stimuli and some sort of behavioral response become connected
TWO TYPES:
-Classical conditioning: when we learn that two types of events go together, such as walking in rain
and wetness
-Operant conditioning: when we learn that a behavior leads to a particular outcome, such as
studying leads to better grades. Skinner more interested in this.
Rise of learning theory
-Rise due to dissatisfaction with use of verbal reports to assess mental states (Freudian ideas…dream
analysis, free association)
Watson
-Started school of behaviorism: based on belief humans and animals are born with potential to learn
anything
oBased on John Locke’s idea of “tabula rasa” blank slate
-environment was SOLE determinant of learning
-He was involved by Ivan Pavlov (who won Nobel Prize for his work on digestive system)
osalivary reflex, salivation at sight of a bowl is NOT automatic, acquired through experience
Neutral stimulus
- unrelated to salivary reflex, ringing bell
Classical or Pavlovian conditioning
- when a neutral object causes reflexive response when associated with stimulus that already has that
response
-means by which animals come to predict the occurrence of events
-passive
oUR (unconditioned response): salivation with food alone
oUS (unconditioned stimulus): food
oCS (conditioned stimulus): only after training
oCR (conditioned response): salivary reflex (learned response)
Note
-UR and CR not identical
-US produces more saliva than CS
-CR usually less strong than UR
-stimulus that occurs before US is more easily conditioned than one that comes after it
obecause one before predicts it
Acquisition
-gradual formation of an association between conditioned and unconditioned stimuli
-CRITICAL element is contiguity: stimuli occur together in time
-Subsequent research has shown best if very brief DELAY between CS and US
Extinction
-CR is weakened when CS is repeated without US
o the response is extinguished when CS no longer predicts US
oextinction inhibits but does not break the associative bond
Spontaneous recovery
-previously extinguished response reemerges following presentation of CS
-temporary but quickly fade unless CS is again paired with US
-even single pairing of CS with US will reestablish CR
Stimulus generalization
-when stimulus is similar but not identical to CS produce the CR.
Stimulus discrimination
-animals learn to differentiate between two similar stimuli if one is consistently associated with US and
other is not
Second-order conditioning
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-sometimes CS not directly associated with US but with other stimuli that are associated with US
-accounts for complexity of learned associations among people
-most occurs implicitly, without our awareness or intention
Classical conditioning explains phobias and addictions
Phobia
-ACQUIRED fear that is out of proportion to the real threat
-according to classical conditioning, develops through generalization of a fear experience
Fear conditioning
-classically condition animals to fear neutral objects
-without amygdale, no fear conditioning
Counter conditioning
-exposing people to small doses of fear stimulus while engaging in pleasurable task helps overcome
phobia
-formal treatment based on this is systematic desensitization
oasked to imagine feared object while doing relaxation exercises
oCS CR1 (fear) connection can be broken by CSCR2 (relaxation) connection
Drug addiction
-Conditioned withdrawal effects: addicts quitting drugs in rehab often relapse when returned to
old environment
oWhen addicts exposed to environmental cues associated with their drug use, experience
craving and physiological sensation similar to withdrawal
ocues activated prefrontal cortex and various regions of limbic system, involved in emotion and
motivation
oTolerance: addicts need more and more of a drug to experience the same effects
greatest when drug is taken in same location as previous drug use, over wise may risk
overdose
Equipotentiality
-idea that all stimuli are equally capable of producing conditioning (Pavlov)
-WRONG
-Certain pairings more likely than others
oeasier to condition monkeys to fear snakes than flowers or rabbits
ocontiguity not enough to create CS-US associations
-Biological preparedness: animals are genetically programmed to learn to fear specific objects
Rescorla-Wagner model
-a cognitive model of classical conditioning that states that the strength of the CS-US association is
determined by the extent to which the US is unexpected.
-greater surprise of US, more effort to predict it in future
-so greater classical conditioning of surprising event (CS) that predicted US
-conditioning is a process where learn to expect the US based on the CS
-novel stimuli more easily associated with the US rather than familiar stimuli
oonce learned, CS can prevent acquisition of new CS, blocking effect
oe.g. dog that has acquired smell of almonds CS as good predictor of food US does not need to
look for other predictions
ostimulus associated with CS can act as an occasion setter or trigger for CS
dog learns smell of almonds (CS) predicts food (US) only when preceded by flash of
light. The light indicates whether CS-US association is active
Operant (instrumental) Conditioning
-learning process in which the consequences determine the likelihood an action will be performed in
the future
-Skinner
othought BEHAVIOR occurs b/c it has been REINFORCED
olearn to behave to be rewarded and avoid being punished
oHis Utopia bookall problems solved through operant conditioning
-Many of our actions are instrumental, done for a purpose
-Device for assessing operant conditioning
oSkinner box: response key connected to food or water supply
oMade skinner box or operant chamber because tired of fetching rats
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