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Module 18
Classical Conditioning (cont’d)
Processes of Conditioning
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Acquisition
Extinction
Spontaneous Recovery
Stimulus Generalization/ Discrimination
Spontaneous recovery
™ The re-emergence of an extinguished CR after a
period of rest
Classical Conditioning
ƒ Generalization
ƒ tendency for stimuli similar to CS to elicit similar
responses
ƒ Can be adaptive- as children taught to fear moving cars on
street to respond similarly to trucks and motorcycles on the
street
ƒ Discrimination
ƒ in classical conditioning, the learned ability to
distinguish between a CS and other stimuli that do
not signal a US
ƒ E.g., fear pitbulls but not golden retrievers
ƒ Lightning but not flashing disco lights
Updating Pavlov’s understanding
ƒ Role of mental processes
ƒ Thought/expectation of the CS-US link matters for
conditioning
ƒ Consistent link between the CS and US matters
ƒ Role of biological dispositions
ƒ Each species’ biological dispositions prepare it to
learn the associations that enhance its survival
ƒ Taste aversion (rather than sight) in rats - they are
biologically prepared to learn associations between the taste
of a particular food and the onset of an illness, but not
between sights and sounds and an illness.
Classical Conditioning:
Key Points
ƒ CC prepares us for significant events by
identifying events that commonly predict them
ƒ Can explain a wide range of behavior
ƒ Advertising, food aversion, phobias
ƒ Focuses on naturally occurring responses
ƒ Not under voluntary control
ƒ Any naturally occurring behavior (or response) can be
conditioned to neutral stimulus
ƒ Eye blink — bell
ƒ Sexual arousal — perfume
How far does the power of CC
spread?
™ Pictures rates as similar / neutral by a group of judges
™ Then these faces were presented to a new group – each
picture was paired with either a pleasant, neutral, or
unpleasant odor.
™ When later asked to evaluate the faces the subjects the
highest ratings were given to those pictures that had been
associated with the pleasant odor.
™ The lowest ratings were given to those pictures which had
been paired with the unpleasant odor
(Todrank, Byrnes, Wrzesniewski, & Rozin, 1995)
Module 19 - Operant Conditioning
Learning that behaviors are associated
with their consequences
Operant Conditioning
ƒ Behaviors are associated with their
consequences
ƒ Learning in which behavior [operant] is
strengthened if followed by a reinforcer
and weakened if followed by a punisher
ƒ What is a reinforcer?
ƒ What is a punisher?
Important: Reinforcers and punishers are
defined by their effects on behavior, not by
your intentions
™Example: Ali is acting out while his mother is
watching Seda Sayan show. His mother turns
around and tells him to stop, but Ali increases the
noise he makes. His mother scolds him. Ali
becomes even more active and louder. His mother
spanks him, and Ali starts shouting and jumping up
and down on the sofa.
History of Operant Conditioning:
Thorndike’s (early 20th century) Law of
Effect
ƒ Behaviors followed by favorable consequences
become more likely, and behaviors followed by
unfavorable consequences become less likely
Thorndike's Law of Effect
Strengthens
Good
Outcome
Behavior
Weakens
Bad
Outcome
Skinner’s (late 20th century)
behavioral technology
ƒ Operant chamber / Skinner box
ƒ Using behavioral technology, Skinner could teach
pigeons to walk on a figure 8, play ping pong, or play
simple computer games
How to strengthen behavior:
Reinforcement
™Provide a reward = positive stimulus
ƒ If presented AFTER a response, it strengthens the
response
ƒ E.g., food, pleasurable sensation, …
™Take away something that is undesirable or
unpleasant = reduce negative stimulus
ƒ If removed AFTER a response, it strengthens the
response
ƒ E.g., A whining child being quiet, seat belt warning
sound not beeping, alarm clock going quiet
Reinforcer
ƒ any event/stimulus that strengthens, or
increases the likelihood of a prior response.
ƒ Two kinds:
ƒ Positive reinforcer: presentation of a positive
stimulus
ƒ Negative reinforcer: removal of a negative
stimulus
Types of Reinforcers
™Primary Reinforcer
ƒ innately satisfies a biological need
ƒ Food, security, positive feelings
™Conditioned (secondary) Reinforcer
ƒ stimulus that is reinforcing because it is associated with a
primary reinforcer
ƒ Money, good grades, words of praise, pleasant tone of voice
In real life we are not continuously and
immediately reinforced.
ƒ Immediate reinforcers are the only ones that work with
most animals.
ƒ Humans do respond to delayed outcomes.
ƒ E.g. Good grades at the end of the semester
ƒ E.g. Salary at the end of the month
ƒ Requires requires cognitive engagement.
ƒ People may need to choose between immediate – smaller
consequences & delayed- bigger consequences.
ƒ Chocolate cake now – or losing weight in a month.
ƒ Smoking now – lung cancer in 30 years?
Schedules of Reinforcement
ƒ Continuous Reinforcement
ƒ reinforcing the desired response each time it occurs
ƒ learning occurs rapidly
ƒ Partial (Intermittent) Reinforcement
ƒ reinforcing a response only part of the time
ƒ results in slower acquisition but greater resistance to
extinction
ƒ can be rewarded based on frequency of behavior
(fixed ratio or variable ratio)
ƒ can be rewarded based on the time interval (fixed
interval or variable interval)
Vary number of responses required
™Fixed Ratio Schedule: reinforces a response
after a specified number of responses
ƒ faster you respond the more rewards you get (e.g.
piecework pay, frequent flyer programs)
ƒ very high rate of responding because resting reduces
rewards
™Variable Ratio Schedule: reinforces a response
after an unpredictable number of responses
ƒ very hard to extinguish because of unpredictability
ƒ very high rate of responding because resting reduces
rewards (e.g. gambling, fishing)
Vary time of interval
™Fixed Interval: reinforces a response after a
specified time has elapsed
ƒ response occurs more frequently as the anticipated
time for reward draws near (e.g. Monthly payments,
checking to see if the cake is baked, studying hardest
before the mid term)
™Variable Interval: reinforces a response at
unpredictable time intervals
ƒ produces slow steady responding (e.g. pop quiz,
checking for email from a loved one)
Schedules of Reinforcement
Number of
responses
1000
Fixed Ratio
Variable Ratio
Fixed Interval
750
Rapid responding
near time for
reinforcement
500
Variable Interval
250
Steady responding
0
10
20
30
40
50
Time (minutes)
60
70
80
How to weaken a behavior:
Punishment
™A punisher decreases the frequency of the
preceding behavior
ƒ An unpleasant or undesirable stimulus will powerfully
reduce unwanted behavior
™How can we punish?
ƒ Positive punishment: Provide an unwanted stimulus
ƒ Negative punishment: Take away a desired or
wanted stimulus
Teaching complex behaviors: Shaping
™A procedure in which reinforcers guide behavior
towards gradually closer approximations of the
desired behavior.
ƒ Build on existing behaviors that occur by chance
ƒ Make rewards contingent on closer approximations
Operant vs Classical Conditioning