Learning
Learning Learning Behaviorism Psychology is the “science of behavior.” Emphasis on what can be directly observed. Ignore the mind (unobservable).B. F. Skinner Emphasis in Reinforcements / Rewards Mental Processes Stimulus Behavior (Response) 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 Reflex Salivation Not Reflex Learned behavior! Footsteps Food bowl Bell 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 Neutral Stimulus (i.e., bell) Stimulus (i.e., food) Reflexive response (i.e., salivation) Classical conditioning Neutral Stimulus (i.e., bell) Stimulus (i.e., food) Reflexive response (i.e., salivation) 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 Different stages of classical conditioning Classical conditioning Little Albert (8-month old infant) Neutral Stimulus (i.e., white rat) Stimulus (i.e., loud noise) Reflexive response (i.e., startled & cry) 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 Neutral Stimulus (i.e., needle, back alley) Stimulus (i.e., drug) Reflexive response (i.e., physiological response) 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 Operant conditioning Reward Increase in behavior Activates reward system (n. accumbens) Punishment (or no reward) Decrease in behavior 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 conditioning Reinforcement — a positive consequence that follows a behavior Punishment — a negative consequence that follows a behavior Change in environment Likelihood to repeat behavior increase decrease positive reinforcement positive punishment (get to use car more often) (additional hassle) stimulus negative reinforcement negative punishment removed (no longer dependent on (take away driving parents) privileges) stimulus added Operant conditioning How to measure effects of reinforcement/punishment? Change in environment Likelihood to repeat behavior http://www.cs.tcd.ie/research_groups/crite/personal/imgs/skinner3.gif stimulus added stimulus removed increase decrease positive reinforcement positive punishment (water) (foot shock introduced) negative reinforcement (foot shock removed) negative punishment (water removed) Operant conditioning How 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 Initial behavior Sitting Standing Standing on hind legs Standing near lever Sniffing lever Desired behavior Pressing lever Operant conditioning What 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 conditioning How often should a reinforcer be given? Reinforcement schedules continuous reinforcement partial reinforcement (i.e., desired behavior is (i.e., desired behavior is reinforced every time) reinforced intermittently) Operant conditioning Reinforcement schedule Partial reinforcement Ratio Fixed Interval Variable Ratio Fixed Variable Fixed Variable Interval every 5th lever press every 20 seconds 3rd, 8th, 19th, 20th, 35th 2s, 8s, 34s, 36s, 40s Predictable Unpredictable Operant conditioning How 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 Figure 6.6 Limitations of conditioning theories 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 Remember, conditioning theories state that ... • Reinforcement is necessary for learning to occur http://psychclassics.yorku.ca/Tolman/Maps/FIG1.gif Limitations of conditioning theories Latent learning No food No food (first 10 days) No food Continuous food Continuous food No food (first 10 days) Learning took place even when there was no reinforcement Learning was revealed after behavior was reinforced Limitations of conditioning theories Learning through observation (in humans): • Albert Bandura’s Bobo doll experiment 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 http://academic.evergreen.edu/h/hiljus01/bobo.gif Bobo doll Limitations of conditioning theories 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 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 Operant conditioning Classical conditioning • Association between neutral and reflexive stimuli leads to learning • Passive process • 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 Figure 6.11 Figure 6.12
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