Transcript Chapter Six

Chapter Six
Learning
What Is Learning?
• Adaptive process through which
experience modifies pre-existing behavior
and understanding.
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Adaptation to a constant
stimulus is simple learning
Reponses to unchanging stimuli decreases
over time.
– Habituation is simplest form of learning.
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Non-Associative Learning
• Learning results from the impact of one
particular stimulus.
– Not the result of learning to associate one
stimulus with another (i.e. habituation.)
– We learn to ignore repeated stimuli
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Another example of nonassociative learning
• Why do people engage in risky behavior?
• Solomon’s (1980) Opponent Process
Theory explains this – Based on disruption
and restoration of equilibrium.
• Explains drug addiction, bungee jumping,
and maybe even self destructive
gangbanging behavior.
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Solomon’s Opponent-Process
Theory
– New stimuli that cause extreme positive or negative
feeling cause opposite (opponent) feeling to occur
to restore equilibrium.
– If new stimulus is repeated the opponent feeling
happens faster and stronger, eventually
suppressing original stimulus.
– i.e. Drug addiction – over time addicts need more
drug to get the same effect (habituation), and
withdrawal gets worse over time too.
– i.e. Why do people skydive, ride rollercoasters?
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Associative Learning
Most learning theories are based on
associations of one stimulus with another,
or associations between behavior and its
consequences.
Classical Conditioning
- Ivan Pavlov, John B. Watson
Instrumental & Operant Conditioning
- Edward Thorndike, B.F. Skinner
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Ivan Pavlov - Classical
Conditioning
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Pavlov’s Classical Conditioning
• Start with Unconditioned Stimulus UCS
– Causes an instinctive Unconditioned Response UCR
– For example, food causes salivation (drooling)
• Then PAIR the UCS with a Neutral Stimulus
– Presenting the UCS with Neutral Stimulus causes an
association to form. The more you do it, the stronger
the association.
– Ex., ring a bell when you present food…
– Eventually the bell ALONE will cause salivation
• The bell was neutral, but is now a Conditioned
Stimulus CS which causes salivation, the
Conditioned Response CR
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Classical Conditioning –
UCS, UCR, CS, CR
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Apparatus for Measuring
Conditioned Responses
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Little Albert – John Watson
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Changes Over Time in the Strength
of a Conditioned Response:
Extinction and Spontaneous
Recovery
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Stimulus Generalization - Pavlov
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Stimulus Discrimination
• What if there were no limits to stimulus
generalization?
• Stimulus Discrimination: Learning to
differentiate among similar stimuli.
– Complementary (opposite) process to
stimulus generalization.
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Factors Affecting the Learning of
a Conditioned Response
• Timing
– Forward conditioning = CS then UCS
• Most effective (bell then food0
– Backward conditioning = UCS then CS
• Less effective (food then bell)
– Simultaneous conditioning = Same time
• Least effective (food and bell at the same time)
• Predictability
• Signal Strength
• Attention to Stimulus
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More Factors Affecting the Learning
of a Conditioned Response
• Second-Order Conditioning
– i.e. Dr.’s waiting room (cs) and shot (ucs)–
waiting room could begin to act as ucs…
eventually magazines become cs.
– While adaptive, can cause problems.
• Biopreparedness
– Animals are predisposed to certain
conditioning situations… perhaps genetic.
– i.e. taste aversions, snakes vs. cars.
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Some Applications of Classical
Conditioning
• Can play role in the development of phobias.
(extreme fears that are not based on real danger
or fear reactions that aren’t appropriate to real
danger)
– Systematic desensitization as a treatment – to cause
extinction.
• Predator Control – taste aversion
• Predicting Alzheimer’s Disease – ability of
patients to be conditioned to blink (air puff = ucs,
light =cs) deteriorates.
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• Other applications?
Instrumental and Operant
Conditioning: Learning the
Consequences of Behavior
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Edward L. Thorndike 1898
• Was studying animals’ intelligence and
ability to solve problems.
– Used a puzzle box.
• What were Thorndike’s cats learning?
– “Law of effect” – Consequences change
behavior.
– Described this kind of learning as instrumental
conditioning. – Organisms learn to do things
that have satisfying or pleasurable
consequences.
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Figure 6.5: Thorndike’s Puzzle
Box
Return
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B. F. Skinner - Operant Cond.
• Extended and formalized many of
Thorndike’s ideas.
• Organisms learn responses by operating
on the environment.
– “Operant conditioning”
• Primary aim was to analyze how behavior
is changed by its consequences.
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Basic Components of Operant
Conditioning
• Operant – a response that has an effect on the
world.
• Reinforcer – a stimulus that increases the
probability that the behavior which preceded it
will occur again.
– Positive reinforcer – a pleasurable thing follows
behavior – ie: Mom gives kid candy for good
behavior in store (kid is being conditined)
– Negative reinforcer – an unpleasurable thing
STOPS following behavior. ie: Kid stops whining
when mom gives them candy in checkout line (mom
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is being conditioned)
Figure 6.6: Positive and
Negative Reinforcement
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Escape and Avoidance: Two types
of negative reinforcement
Escape
Conditioning
Avoidance Conditioning
Adapted from: The Psychology of Memory and Learning by Hintzman. © 1978 by W.H. Freeman and Company. Used with permission.
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IMPORTANT!!
• Negative reinforcement is NOT punishment.
• Negative reinforcement is the REMOVAL of
unpleasant stimulus when target behavior is
observed (a positive consequence of behavior –
increases behavior)
• Punishment is the introduction of an aversive
(unpleasant) stimulus or removal of a pleasant
stimulus as a consequence of behavior – ( a
negative consequence of behavior - decreases
behavior.
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Operant Conditioning Activity
• Two volunteers
• A bit like “hot and cold” game.
BF Skinner 1904-1990
Operant Conditioning
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Forming and Strengthening
Operant Behavior
• Shaping – Process of reinforcing responses that get
closer and closer to the desired response.
• Primary Reinforcer – meets basic needs i.e food,
water.- Give dog a treat.
• Secondary Reinforcement
– Say “good dog” when you give the dog a treat… eventually
you won’t need so many treats. (money vs. food/shelter…)
– Secondary reinforcers (or “conditioned reinforcers”)
– Greatly expands the power of operant conditioning.
– Depends on what people like… rock concert, opera?
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Delay and Size of
Reinforcement
• Timing of Reinforcer – Usually the shorter
the delay between behavior and
reinforcement, the more effective.
• Size of Reinforcer – Usually the larger the
reinforcer, the more effective.
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Schedules of Reinforcement
• Continuous reinforcement schedule: flip
switch, light goes on every time. – works
well, but not practical in many situations.
• Partial or intermittent reinforcement
schedule. – also work well and more
practical. Flip switch multiple times before
light goes on.
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Partial / Intermittent Schedules
– Fixed Ratio (FR) – every 10th response = FR10
– Variable Ratio (VR) – not as predictable, the ratio
varies, but can be described as the average VR 30
– Fixed Interval (FI) – Reinforces the first response
and then every fixed amount of time later as long as
there is a response. (many jobs pay this way)
– Variable Interval (VI) – Random checks after some
average interval has passed… avid binder check
about every 2 weeks.
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Intermittent Reinforcement
Schedules
Based on Number of
necessary responses
Predictable
Unpredictable
(“On the
Average”)
Based on Time that must
first pass
Fixed Ratio
(FR)
Fixed Interval
(FI)
Variable Ratio
(VR)
Variable Interval
(VI)
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Effectiveness of Different
Schedules of Reinforcement
Adapted from "Teaching Machines" by B.F. Skinner, Copyright © 1961 by Scientific American, Inc.
All rights reserved.
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Schedules and Extinction
• Failure to reinforce a response
extinguishes that response.
• Partial Reinforcement Extinction Effect
– Explains why superstitious behaviors are
resistant to extinction.
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Self Stimulation – James Olds
• Pleasure Center in brain – Median
Forebrain Bundle
•
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Punishment
• Reduces the frequency of an operant
behavior by presenting an unpleasant
stimulus or removing a pleasant one.
– Two kinds of punishment.
• Negative Reinforcement vs. Punishment
– Negative reinforcement: Strengthens
behavior.
– Punishment: Weakens behavior
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Figure 6.10: Two Kinds of
Punishment
Return
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Potential Drawbacks of
Punishment
• Does not “erase” an undesirable habit;
merely suppresses it.
• Sometimes produces unwanted side
effects.
• Often ineffective unless given immediately
after the response and each time the
response is made.
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Potential Drawbacks of
Punishment (cont’d.)
• Can become aggression, even abuse, if
administered in anger.
• Children are more likely to behave
aggressively if frequently punished.
• Signals what is inappropriate behavior but
does not specify correct alternative
behavior.
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Guidelines for Effective
Punishment
• Specify why punishment is being given.
• Without being abusive, punishment should
be immediate and noticeable enough to
eliminate the undesirable behavior.
• Identify and reinforce more appropriate
behaviors.
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Cognitive Processes in Learning
• Behaviorists: Not interested in role of
conscious mental activity in learning.
• Cognitive Psychologists: Learning may
also result from mental processes.
– Classical and operant conditioning helps to
detect causality.
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Learned Helplessness
• Tendency to give up any effort to control
the environment after experience suggests
that no control is possible.
• First demonstrated in animals.
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Observational Learning
• Learning by Watching Others
– Also called social learning.
• Bandura’s “Bobo” Doll Experiment
• Powerful source of the socialization
process.
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Observation
al Learning
Bandura, A., Ross, D., & Ross, S. A. (1963).
Imitation of film-mediated aggressive models.
Journal of Abnormal and Social Psychology, 66,
3-11.
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Main Learning Theories
• Classical Conditioning
– Pairing stimuli leads to conditioned responses
– Pavlov, Watson
• Operant Conditioning
– Behavior is shaped by its consequences
– Schedules of reinforcement
– Thorndike, Skinner
• Observational Learning
– People learn by watching others and observing the
consequences others receive
– Bandura
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