Transcript Chapter 5

Chapter 5:
Classical Conditioning:
Underlying Processes
and Practical Applications
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
S-R Model
• the NS becomes directly associated with the UR
and therefore comes to elicit the same response
as the UR.
• The purpose of the US is simply to elicit the UR
so that it occurs in close proximity to the NS.
• Example:
– When bitten by a dog, a child associates the dog (NS)
with the pain and fear (UR) that were elicited by the
bite (US).
– She experiences fear (UR) when she next encounters
the dog (CS).
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
S-R Model
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
S-S Model
• the NS becomes directly associated with
the US and comes to elicit a response that
is related to the US.
• Example:
– A child who is bitten (US) by a dog (NS)
associates the dog with the bite.
– Because of that association, the child comes
to fear (UR) the dog (CS).
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
S-S Model
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
So which is it?
• Many researchers now believe that both types of
processes may be involved in conditioning.
• Many basic conditioning procedures seem to
cause an association to develop between the NS
and the US.
• Other instances of conditioning seem to involve
the establishment of an S-R association.
• Modern theories of conditioning have generally
emphasized the establishment of S-S
associations.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Stimulus-Substitution Theory
• the CS acts as a substitute for the US.
• Example:
– A tone paired with food results in the tone becoming a
substitute for the food.
– The tone elicits salivation just as the food does.
• It does not always explain the conditioning well.
• Example:
– A rat is exposed to a light & foot shock.
– The rats response is different for the light & shock.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Preparatory-Response Theory
• the purpose of the CR is to prepare the
organism for the presentation of the US.
• Examples:
– The dog salivates to the tone to get ready for food.
– The rat freezes in response to the light to get ready
for the shock.
• In one case, the preparatory response is highly
similar to the UR, whereas in the other case it is
quite different.
• This theory allows for situations in which the CR
and the UR are different.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Compensatory-Response Model
• a CS that has been repeatedly associated with
the primary response (a-process) to a US will
eventually come to elicit a compensatory
response (b-process).
• Example:
– A heroin addict always injects heroin in the presence
of certain environmental cues.
– Heroin decreases blood pressure.
– The environmental cues prepare him for heroin by
increasing his blood pressure.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Drug Addiction
• Drug addictions are partly motivated by a tendency
to avoid the symptoms of drug withdrawal.
• Repeated heroin use therefore results in the
following process of conditioning:
Heroin-related: Relaxing effect → Tension &
Cues
of heroin
agitation
NS
US
UR
Heroin-related cues → Tension & agitation
CS
CR
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Drug-Related Cues
• one of the strongest reasons why people
continue to battle cravings long after they have
stopped using a drug.
• An individual who always uses heroin in a
particular environment goes into a rehab
program.
• When she returns home to her usual
environment, she will very likely become
agitated.
• She will be sorely tempted to once more take
heroin to reduce the symptoms.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Drug Tolerance
• You have a habit of always drinking in a particular
setting.
• Various CSs initiate physiological reactions that
compensate for the alcohol you are about to consume.
• As a result, in the presence of these CSs, you have
greater tolerance for alcohol than you would in their
absence.
• If you consume alcohol in an environment where you
typically do not drink, the alcohol could have a much
stronger effect.
• The amount of alcohol you consume is not a reliable
gauge for determining how intoxicated you are.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Rescorla-Wagner Theory
• there is only so much associative value that can
be distributed among the various cues
associated with a US.
• Stronger USs support more conditioning than do
weaker USs.
• Example:
– The preferred food supports a maximum associative
value of 10 units.
– The less preferred food supports a maximum
associative value of 5 units.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Value Notation
Tone (V = 0): Food (Max = 10) → Salivation
Tone (V = 10) → Salivation
• V = associative value
• Max = the maximum associative value that
can be supported by the US once
conditioning is complete.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Overshadowing Effect
[Loud tone + Faint light]: Food → Salivation
(V = 0)
(Max = 10)
Loud tone (V = 9) → Salivation
Faint light (V = 1) → Salivation
• The loud tone now elicits 9 drops of saliva (a
strong CR) while the faint light elicits only 1 drop
of saliva (a weak CR).
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Blocking
Tone (V = 0): Food (Max = 10) → Salivation
Tone (V = 10) → Salivation
[Tone + Light] :
Food → Salivation
(V = 10 + 0 = 10) (Max = 10)
Tone (V = 10) → Salivation
Light (V = 0) → No salivation
• The tone has already acquired that max value.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Overexpectation Effect
• the decrease in the conditioned response that occurs
when two separately conditioned CSs are combined into
a compound stimulus for further pairings with the US.
• Conditioning can be viewed as a matter of building the
subject’s expectations that one event will follow another.
• Presenting the two CSs together leads to an
“overexpectation” about what will follow.
• When this expectation is not fulfilled, the subject’s
expectations are modified downward and each CS in the
compound loses some of its associative value.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Understanding Phobias
• Phobias seem to represent a process of
overgeneralization.
• A conditioned fear response to one event
has become overgeneralized to other
harmless events.
• This was first noted by John B. Watson
and his student (and wife-to-be) Rosalie
Rayner in 1920.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Little Albert
• They conditioned a fear response in an 11month-old infant named Albert.
• Before the training, he seemed to display an
unusual level of emotional stability.
Loud noise → Fear (indicated by startle reaction)
US
UR
Rat → No fear
NS
—
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Fear Conditioning
• They paired the loud noise (US) with the white
rat (NS).
• Throughout several pairings, Albert became
more and more fearful of the rat.
Rat: Loud noise → Fear
NS
US
UR
Rat → Fear (indicated by crying & crawling away)
CS
CR
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Overgeneralization of Fear
• He showed not only a fear of the rat but
also of
– a rabbit,
– a fur coat,
– a dog, and
– even a Santa Claus mask.
• His fear response had generalized to
objects that were similar to the original CS.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Real Life Phobias
• Usually the development of phobias
requires only one pairing of the US with
the CS to become established.
• They often grow stronger over time.
• They are not easily countered by the
pleasure derived from other behaviors.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Factors in Phobic Conditioning
• Many people with phobias are unable to recall
any particular conditioning event before the
development of their symptoms.
• Most people exposed to extremely frightening
events do not develop phobias.
• Several factors may be involved, including:
observational learning, temperament,
preparedness, history of control, incubation, US
revaluation, and selective sensitization.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Observational Learning
• Many phobias are acquired through observation
of fearful reactions in others.
• Example:
– children’s fear of air raids and their mothers’ displayed
fear
Display of fear by others → Fear (in oneself )
US
UR
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Temperament
• an individual’s base level emotionality and
reactivity to stimulation.
• Individuals with certain temperaments may
be more genetically susceptible than
others to conditioning.
• Example:
– Jason more easily develops a phobia than
does Samantha.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Preparedness
• a genetically based predisposition to
develop fears to certain types of objects or
events more easily than others.
• Example:
– A phobia of snakes is more easily acquired
than a phobia of toasters.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
History of Control
• Living in an environment where you have
some degree of control over important
events seems to effectively immunize you
against the traumatic effects of
encountering frightening events.
• Example:
– Young monkeys and toy monsters
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Incubation
• the strengthening of a conditioned fear
response as a result of brief exposures to
the aversive CS.
• Example:
– a child who is bitten by a dog and then runs
away each time he encounters a dog
• This may be the reason for the old adage
that if you fall off a horse you should
immediately get back on.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
US Revaluation
• can occur three ways:
• Exposure example:
– skateboarding and minor sever injury, car accident
and major injury
• Observational Learning Example:
– witnessing accidents on the ski slopes
• Verbal Debriefing Example:
– individuals who have been exposed to a traumatic
event and are then given psychological debriefings
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Selective Sensitization
• an increase in one’s reactivity to a
potentially fearful stimulus following
exposure to an unrelated stressful event.
• Example:
– an individual going through a stressful divorce
suddenly develops severe anxiety in traffic
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Treating Phobias
• Systematic Desensitization
• Flooding
• Hybrid Approaches
– exposure-based treatments or exposure
therapies, in vivo exposure
– participant modeling, contact desensitization,
or guided participation
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Systematic Desensitization
• a behavioral treatment for phobias that involves
pairing relaxation with a succession of stimuli
that elicit increasing levels of fear.
• Mary Cover Jones (1924) with 2-year old Peter
• First she fed Peter cookies while presenting a
rabbit at a considerable distance.
• Over successive sessions, the rabbit was
gradually brought closer to Peter as he
continued to eat cookies.
• Within a few months, Peter was holding the
rabbit in his lap.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Counterconditioning
• a CS that elicits one type of response is
associated with an event that elicits an
incompatible response.
• Example:
– Wolpe’s room for feeding and the shock
• The underlying process is reciprocal inhibition, in
which certain responses are incompatible with
each other, and the occurrence of one response
necessarily inhibits the other.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Wolpe’s Treatment Procedure
1. Training in relaxation.
2. Creation of a hierarchy of imaginary scenes
that elicit progressively intense levels of fear.
3. Pairing of each item in the hierarchy with
relaxation.
•
•
He emphasized the use of imaginary stimuli.
It can also be used with in vivo desensitization
meaning you work with a real-life stimulus.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Effective Systematic
Desensitization
• It works with patients who have relatively
few phobias that are specific in nature.
• This is not for people who suffer from
social phobias, which tend to be general in
nature.
• When using imaginal desensitization, the
client must be able to clearly visualize the
feared event and experience anxiety while
doing so.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Flooding
• a behavioral treatment that involves
prolonged exposure to a feared stimulus.
• It provides maximal opportunity for the
conditioned fear response to be
extinguished.
• Two basic types of flooding procedures:
– Imaginal flooding
– In vivo flooding
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Imaginal Flooding Procedures
1. The client visualizes the scenario in the therapist’s
office.
2. The client practices visualizing it at home.
– The fear should eventually begin to decrease and finally will be
extinguished.
3. Once the fear response to one scenario has been
extinguished, the fear response to other scenarios can
be similarly extinguished.
4. After extinction has occurred in several scenarios, the
client will likely experience considerably less fear when
encountering the feared event in the real world.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
In vivo Flooding Procedures
• The client experiences prolonged exposure to
the actual feared event.
• Example:
– A woman is extremely fearful of balloons.
– The woman enters a room full of balloons and closes
the door.
– She remains inside the room for an hour or more.
– After a few sessions of this, her fear of balloons might
be eliminated.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Concerns about Flooding Therapy
• In vivo flooding can be highly aversive.
• Imaginal flooding may be hard to generalize
from an imagined encounter to a real encounter
and it is dependent on a person’s visualization
ability.
• The stress involved may result in medical
complications.
• The duration of each exposure be sufficiently
long (at least 30 to 45 minutes).
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Exposure Therapy
• an in vivo exposure procedure
• Clients are encouraged to approach the feared
object as closely as possible.
• They remain there until the anxiety fades away.
• They then approach the object even more
closely.
• This continues until the client approaches the
object closely and reports the level of fear has
been reduced by 50% or more.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Participant Modeling
• also called contact desensitization or
guided participation.
• The clients are accompanied by the
therapist who acts as a model to
demonstrate to the client how to interact
with the feared object.
• The therapist touches the object first and
then the client. Eventually the therapist
removes her hand.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Aversion Therapy
• reduces the attractiveness of a desired event by
associating it with an aversive stimulus.
• Some behavior problems stem from events
being overly enticing rather than overly aversive.
• Examples:
– Alcohol can be paired with painful electric shocks or
emetics, nausea-inducing drugs.
– Pictures of sex offenders’ desires may be paired with
paired with emetics or a powerfully unpleasant scent.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Covert Sensitization
• aversion therapy carried out with the use of
imaginal stimuli rather than real stimuli.
• Example:
– a person addicted to smoking might imagine
experiencing extreme illness and vomiting each time
she tries to smoke.
• This therapy is dependent on the client’s ability
to visualize images clearly and to experience
strong feelings of revulsion in response to these
images.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Allergic Responses
Flowers: Pollen → Allergic reaction
NS
US
UR
Flowers → Allergic reaction
CS
CR
• The mere sight of flowers elicits an allergic
reaction.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Weakening Immune Responses
Hospital: Chemotherapy → Immunosuppression
NS
US
UR
Hospital → Immunosuppression
CS
CR
• The hospital environment had become associated
with the immunosuppressive effect of the
chemotherapy and is a CS for a conditioned
immunosuppressive response.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Strengthening Immune Responses
Sweet sherbet: Adrenaline → increase immunity
NS
US
UR
Sweet sherbet → increase immunity
CS
CR
• The sweet sherbet elicits an increase in
natural killer cell activity.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Medical Conditioning
• Many patients would benefit considerably from
enhanced immune functioning.
• Other patients would benefit from a procedure
that could reliably weaken their immune system.
• Classical conditioning can also explain the
placebo effect.
• Placebos could then be used to reduce the
frequency with which a patient has to take the
real drug.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Placebo Effect
White pill: acetylsalicylic acid→ No Headache
NS
US
UR
White pill → Headache removal
CS
CR
• Such effects are much more likely to occur
following a period of treatment with the active
drug.
• Repeated administration of a placebo by itself
tends to reduce its effectiveness.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Summary
• S-S approach vs. S-R approach
• Stimulus-Substitution Theory
• Preparatory-Response Theory and the
Compensatory-Response Model
• Rescorla-Wagner Theory
• Classical conditioning is useful in
understanding and treating phobias.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Summary, continued
• Several factors impact phobia
development, including
– observational learning,
– temperament,
– preparedness,
– history of control,
– incubation,
– US revaluation, and
– selective sensitization.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Summary, continued
• Treatment for phobias include:
– Systematic desensitization
– Flooding
– Exposure
• Aversion therapy attempts to reduce the
attractiveness of a desired event by associating
it with an aversive stimulus.
• Each therapy above can be done in vivo or with
imaginary stimuli.
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Summary, continued
• Medical implications include
– Allergic responses
– Increased immune response
– Decreased immune response
– Placebo effect
Introduction to Learning and Behavior, 3e
by Russell A. Powell, Diane G. Symbaluk, and P. Lynne Honey
Copyright © 2009 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.