learning. stimulus behavior mental processes behaviorism psychology is the “science of...
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Learning
Stimulus Behavior
Mental Processes
BehaviorismPsychology is the “science of behavior.”
Emphasis on what can be directly observed. Ignore the mind (unobservable).
Emphasis in Reinforcements / Rewards
(Response)
B. F. Skinner
Classical conditioning
Ivan Pavlov (early 1900s)
• Russian physiologist
• Nobel prize winner for his work on the digestive system
» Interested in the salivary reflex
» Do different types of food elicit different amount of saliva?
http://www.mphy.lu.se/avd/nf/hesslow/bilder/pavlov.jpg
Classical conditioning
Food Salivation
Footsteps
Food bowl
Bell
Salivation
Reflex
Not ReflexLearned behavior!
Classical conditioning
How does classical conditioning work?
Step 1: Find a stimulus that elicits a reflexive behavior
Step 2: Pair stimulus with a neutral stimulus that does not normally elicit the same reflexive behavior
Step 3: Over time, if neutral stimulus always signals the original stimulus, the previously neutral stimulus will now elicit the reflexive behavior
Stimulus(i.e., food)
Reflexive response(i.e., salivation)
Neutral Stimulus(i.e., bell)
Classical conditioning
Stimulus(i.e., food)
Reflexive response(i.e., salivation)
Neutral Stimulus(i.e., bell)
Food — Unconditioned stimulus (UCS)
Salivation — Unconditioned response (UCR)
Bell — Conditioned stimulus (CS)
Salivation (in response to bell) — Conditioned response (CR)
Classical conditioning
What are the requirements for classical conditioning to work?
• The conditioned stimulus (i.e., bell) must be previously neutral
• Contiguity during acquisition
» the CS must come immediately before the UCS
» The CS should signal the UCS
• Contingency
» If the CS no longer signals the UCS reliably, the CR will stop (i.e., extinction)
• Spontaneous recovery
» Even after extinction, it is possible to re-establish the CS - CR relationship
If all of these conditions are followed, any neutral stimulus has the potential to become a conditioned stimulus
Classical conditioning
Little Albert (8-month old infant)
Stimulus(i.e., loud noise)
Reflexive response(i.e., startled & cry)
Neutral Stimulus(i.e., white rat)
Stimulus generalization
• Previously neutral stimuli that are similar to the CS will now elicit the CR
Click here for video
Classical conditioning
Classical conditioning in humans
“Give me a dozen healthy infants, well formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select —doctor, lawyer, artist, merchant-chief, and yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations and race of his ancestors.”
- John B. Watson, 1924, Behaviorism
What a freak!
Classical conditioning
Application of classical conditioning theories: Drug addiction
Stimulus(i.e., drug)
Reflexive response(i.e., physiological response)
Neutral Stimulus(i.e., needle, back alley)
Classical conditioning
But ... classical conditioning doesn’t explain all learning
• Not all unconditioned stimuli are equal
» Some fears are easier to condition than others
• Does not account for reward and punishment
http://www.theage.com.au/ffximage/2007/04/16/snake,0.jpg; http://www.sunbeamhospitality.com/resources/images/products/3278-500-600/3278int_xlg.jpg
Operant conditioning
Operant (instrumental) conditioning
• All actions serve some purpose
• We learn to behave in a certain way because those behaviors lead to rewards
• We learn NOT to behave in a certain way because those behaviors lead to punishment (or no reward)
• Consequences matter
Operant conditioning
Reward Increase in behavior
Punishment(or no reward) Decrease in behavior
Activates reward system (n. accumbens)
Operant conditioning
B. F. Skinner
• The organism behaves in a certain way in order to change the environment
» not merely a passive recipient of the conditioned stimulus
» behaviors repeat because they have been reinforced
» consequence of behavior matters
http://www.bfskinner.org/images.asp
Operant conditioningReinforcement — a positive consequence that follows a behavior
Punishment — a negative consequence that follows a behavior
Likelihood to repeat behavior
Cha
nge
in e
nviro
nmen
t
increase
reinforcement
reinforcement
decrease
punishment
punishmentpositive
stimulus
added
positive
negative
stimulus
removed
negative
(get to use car more often)
(no longer dependent on
parents)
(additional hassle)
(take away driving
privileges)
Operant conditioning
How to measure effects of reinforcement/punishment?
http://www.cs.tcd.ie/research_groups/crite/personal/imgs/skinner3.gif
Likelihood to repeat behavior
Cha
nge
in e
nviro
nmen
t
increase decrease
positivereinforcementstimulus
added
stimulus removed
negativereinforcement
positivepunishment
negativepunishment
(water)
(foot shock removed)
(foot shock introduced)
(water removed)
Operant conditioningHow do you get the animal to do what you want to begin with?
• Shaping
» Successive approximation — reward behavior that is similar to the desired behavior
Desired behavior Pressing lever
Initial behavior Sitting
Standing
Standing on hind legs
Standing near lever
Sniffing lever
Operant conditioningWhat does it take for operant conditioning to work?
• Reinforcers must be presented immediately after the behavior
» Primary reinforcer — fulfills basic needs (e.g., food, water)
» Secondary reinforcer — more abstract (e.g., money, fame)
• Delivery of the reinforcer must be consistent
Operant conditioningHow often should a reinforcer be given?
Reinforcement schedules
continuous reinforcement(i.e., desired behavior is
reinforced every time)
partial reinforcement(i.e., desired behavior is
reinforced intermittently)
Operant conditioning
Reinforcement schedule
Partial reinforcement
Ratio Interval
Fixed Variable Fixed Variable
RatioInterval
Fixed
Variable
every 5th lever press every 20 seconds
3rd, 8th, 19th, 20th, 35th 2s, 8s, 34s, 36s, 40s
Predictable
Unpredictable
Operant conditioningHow is behavior influenced by the different schedules?
Casinos use variable ratio reinforcement
Limitations of conditioning theories
But ... conditioning theories do not explain all learning
• One trial learning: taste aversion
» A rat given sweetened water before radiation (which causes nausea) will later avoid
sweetened water, even after just one exposure
• Insight learning» Kohler’s experiment
Video _pigeon
But ... conditioning theories do not explain all learning
• Remember ... Skinner claimed that learning is a result of reinforcement
• If that’s true, then unreinforced behaviors should not be learned
» Latent Learning (Edward Tolman)
» Trained rats to run mazes
» Will rats learn without reinforcements?
Limitations of conditioning theories
Latent learning: Will rats learn without reinforcements?
• Train rats to run a maze under 3 conditions:
» continuous reinforcement
» no food reward until the 11th day
» no food reward ever
Limitations of conditioning theories
http://psychclassics.yorku.ca/Tolman/Maps/FIG1.gif
Remember, conditioning theories state that ...
• Reinforcement is necessary for learning to occur
Latent learning
Limitations of conditioning theories
No food
No food (first 10 days)
Continuous food
No food
No food (first 10 days)
Continuous food
Learning took place even when there was no reinforcement
Learning was revealed after behavior was reinforced
Learning through observation (in humans):
• Albert Bandura’s Bobo doll experiment
Limitations of conditioning theories
Bobo dollhttp://academic.evergreen.edu/h/hiljus01/bobo.gif
Results:
Children who observed violent adult interactions
with bobo doll displayed more aggressive
interactions with the doll than children who
observed non-violent adult interactions with doll
Observational learning video
Learning through observation (in monkeys):
• Monkeys raised in the lab environment did not show fearful responses towards snakes
• Shown footage of other monkeys being fearful of snakes
• Monkeys raised in lab developed a fearful response towards snakes
Limitations of conditioning theories
Conditioning: Phobias- overgeneralization: a dog bit me -> afraid of all dogs afraid of animals afraid of going outside
- role of classical conditioning: CS (dog), US (dog bite) UR (pain, fear)
=> CS (dog) – fear response;
role of operant conditioning: avoid CS (dog) reduces anxiety => continue avoiding CS
- treatment: pair fear stimuli with relaxation (or other pleasurable stimuli)
other things: fear of some stimuli (snakes, heights, dark) more common than others (knives, electrical outlets): argues against equipotentiality, in favor of evolution
-illusory correlation between feared stimulus and negative outcome
Conditioning: Physical punishment by parents
- Should we use punishment to eliminate unwanted behavior? No.
but if you do, do immediate punishment (more effective than delayed punishment, this is true even for your pets!)
Why not use punishment?- more punishment => more aggressive behavior by the child
=> child likely to use physical punishment when he grows up
Does punishment really cause aggression?
Alternatives hypotheses:
- aggression causes punishment
- a third variable (e.g., genetics) causes aggression & punishment
External vs. Intrinsic rewards
Nursery school children
Paper & crayons: draw whatever you want
External reward group: “Good Player Award”
Intrinsic reward group: nothing
External reward increased amount of time drawing, BUT
Ending external reward reduces drawing time below the intrinsic reward group!
should we give students extra-credit for attending talks in their major?
Lepper & Greene, 1978
Operant Conditioning: Infant sleep
Infant Sleep
Extinction is harder to achieve after intermittent reward (partial reinforcement)
- baby cries, dad breaks down and goes in to console the baby:
- baby learns that crying leads to reward (daddy comes)
- to make matters worse, dad only breaks down sometime (partial reinforcement)
Operant Conditioning: other applied issues
- ‘variable ratio’ reinforcement also occurs in casinos
-Operant conditioning is used
- to train animals (flipper, sea world)
- for Token economies in psychiatric hospital: target behavior, reinforcers (sometimes fail to transfer to outside world)
- in Applied behavioral analysis (for autism)
- for Behavior modification (kazdin, slate)
Take home message
Classical conditioning
• Association between neutral and reflexive stimuli leads to learning
• Passive process
Operant conditioning
• Consequences matter
• Takes rewards and punishments into account
• Active engagement with the environment
Limitations to conditioning theories:• Not all unconditioned stimuli are the same
• One-trial learning
• Insight learning
• Latent learning
• Learning through observation
Other things to include:
Classical conditioning example: baby bottle suck
Species specific behavior: racoons & pigs