Transcript Abnormal Psychology - University of Toronto

Introduction to Psychology
Learning
Learning
• Learning refers to an enduring change in the way an
organism responds based on its experience
– Distinct from
• Drug effects (caffeine-induced jitters are not learning)
• Fatigue or illness
• Three assumptions of learning theories
– Responses are learned rather than innate
– Learning is adaptive
– Our experiments can uncover the laws of learning
• These laws will apply to animals and to humans
.
Classical Conditioning
• The Russian physiologist Pavlov noted that reflexive
salivation in dogs could be elicited by stimuli
associated with feeding
– Reflex: Response that is reliably elicited by a stimulus
• Food elicits salivation
• Air puff elicits eye blink
– Reflexive stimulus and response are unconditioned
– Neutral stimulus is referred to as the conditioned stimulus
(CS)
– CS is paired with the UCS over many trials
– Eventually comes to elicit a conditioned response (CR:
resembles the UCR)
Pavlov’s Experiment
Acquisition and Extinction
• Acquisition of classical
conditioning:
– Repeated pairings of CS and
UCS
• Extinction: Refers to the
weakening of conditioning
evident when the CS is
presented repeatedly without
the UCS
– Spontaneous recovery: Refers
to the reemergence of a
previously extinguished CR
Stimulus Generalization and
Discrimination
• Stimulus generalization occurs when an organism
that has learned a response to a specific stimulus
responds in the same way to new stimuli that are
similar to the original stimulus.
• Stimulus discrimination occurs when an organism
that has learned a response to a specific stimulus
does not respond in the same way to new stimuli
that are similar to the original stimulus.
Classical Conditioning Issues
• Temporal order of
presentation of CS
and UCS is important
– Best conditioning:
CS precedes UCS
(forward)
– Worst conditioning:
UCS precedes CS
(backward)
Conditioned Taste Aversion
• If a flavor is followed by an illness
experience, animals will avoid the flavor in
the future
CS
Taste
+
CS ----->
Flavor
UCS ----------> UCR
Toxic event
Nausea
CR
Nausea
Biological Preparedness:
The Garcia Experiment
Some associations are more easily learned than others
(Figure adapted from Garcia & Koelling, 1966)
Positive Reinforcement
• Reinforcer: An environmental stimulus that
occurs after the response and increases the
likelihood that the response will occur in the
future
– Positive reinforcement: Process by which
presentation of a stimulus after a response makes
the response more likely to occur in the future
– Negative reinforcement: Termination of an
aversive event makes a behavior more likely to
occur in the future
Issues in Negative Reinforcement
• Negative reinforcement involves a situation in
which a response that terminates an aversive
stimulus will strengthen that response
– Taking an aspirin will reduce the headache and
strengthen the behavior of aspirin-taking
(sometimes referred to as escape-learning)
– Avoidance learning: A response prevents a
potentially aversive event from occurring
• Child cleans his room to avoid parental nagging
Punishment
• Punishment decreases the likelihood that a response
will occur
• Examples of punishing situations
– Presentation of an aversive stimulus (Positive)
• Parent spanks a child for taking candy...
• Owner swats a dog who has chewed her slippers...
– Removal of a reward (Negative)
• Teenager who stays out past curfew is not allowe d to drive the
family car for 2 weeks...
• Husband who forgets anniversary sleeps on couch for a week...
Difficulties in Punishment
• Learner may not understand which operant
behavior is being punished
• Learner may come to fear the teacher, rather than
learn an association between the action and
punishment (then avoids the teacher)
• Punishment may not undo existing rewards for a
behavior
• Using punishment when the teacher is angry
• Punitive aggression may lead to future aggression
Schedules of Reinforcement
• Continuous reinforcement: Reinforcer is
obtained for every response
– Intermittent schedules: Reinforcer is not obtained
for every response
• Ratio Schedules
– Fixed Ratio: Every Nth response
– Variable Ratio: The average is every Nth response
• Interval Schedules:
– Fixed Interval: After the elapse of N minutes
– Variable Interval: On average, after N minutes
Observational Learning
•
•
•
•
Social Learning Theory (Bandura)
Modeling
Vicarious learning
Acquisition vs. Performance