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Lecture

PSY100H1 Lecture Notes - Classical Conditioning, Nucleus Accumbens, Habituation


Department
Psychology
Course Code
PSY100H1
Professor
doldeman

Page:
of 5
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
-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
Problem with operant conditioning outside Skinner box: need to wait until the animal emits an appropriate
response before you can provide the reinforcer
-shaping: reinforce behavior that is increasingly similar to desired behavior
-become more selective
-reinforcing successive approximations will eventually produce desired behavior, are dog learns to
discriminate which behavior is being reinforced
-best way to condition behavior continuous reinforcement during early acquisition and then slowly
change to partial reinforcement
-biology and cognition influence operant conditioning
-biology places constraints on learning and reinforcement not always present for learning to take
place
Thorndike
-built a PUZZLE BOX, a small cage with trapdoor to study whether animals showed signs of
intelligence. Pg 224
oLaw of effect: any behavior that leads to “satisfying state of affairs” more likely to occur
again and those that lead to “annoying state of affairs” are less likely
oSubjective, can’t be observed empirically according to Skinner
Reinforcer
- stimulus that occurs following a response that increases the likelihood that the response will be
repeated
Primary reinforcers
- innately reinforcing, satisfy biological needs
Secondary reinforcers
- do not directly satisfy biological needs, become reinforcers by repeated pairings with primary
reinforcers
-established through classical conditioning
-e.g. associate neutral stimulus money (CS) with food (US)
Premack’s theory
- Integrative theory of reinforcement: the value of a specific reinforcer could be determined by
the amount of time an organism engages in that behavior when free to choose anything
-accounts for differences in values
-Premack principle: a more valued activity can be used to reinforce the performance of a less
valued activity “finish your homework and then you can go out”
Reinforcement
-Reinforcement increases behavior
ois better than punishment b/c tells child what to do
-Punishment decreases behavior
Positive reinforcement: increases behavior through pleasurable stimulus.
-behaviors that are rewarded increase in frequency
Negative reinforcement: increases behavior through the removal of negative stimulus
-trying to avoid unwanted stimulus
Positive punishment: decrease behaviour through negative stimulus
Negative punishment: decreases behaviour through pleasurable stimulus
Latent learning: learning that takes place in absence of reinforcement.
Punishment
-process by which the consequences of an action reduce the likelihood that the action will be repeated
-must be reasonable, unpleasant and applied immediately in DIRECT response to unwanted behavior
-Sometimes punishment applied after desired action (like student admitting to cheating)
-People learn how to not get caught rather than how to behave appropriately
-spanking, is ineffective
How often should reinforcer be given?
Continuous reinforcement: reinforce every time desired behavior occurs
-behavior gone quickly if reinforcement stopped, i.e. vending machine
Variable-ratio schedule: continue behavior even if rarely reinforce behavior
-Slot machine
Fixed schedule: reinforcer consistently given following specific number of occurrences or specific amount
of time
-workers usually paid at fixed rate, rate is PREDICTABLE
Partial reinforcement: reinforced intermittently, most common