Download SV3 Learning Nov 22 2009

Learning
Ψ 100/101
Nov 20 ‘09
True or False?
1.
Lowly animals, like sea snails, behave by instinct and are incapable of learning.
2.
Humans are the only animals that can learn behaviors merely by observing others
perform them.
3.
The study of inner thoughts, feelings, and motives has always occupied a central
place in psychology.
4.
A person can be more readily conditioned to fear snakes and spiders than to fear
flowers
5.
With training, pigeons can be taught to discriminate a Bach composition from a
Stravinsky composition
6.
Negative reinforcement is another term for punishment.
7.
Psychologists agree that punishment, regardless of its form, has little effect on
Behaviour.
8.
Animals learn only when rewards are given.
9.
Animals can learn to make virtually any response if consistently rewarded for it.
10. Research indicates that televised violence leads to aggressive Behaviour by children
and teenagers who watch the programs
Overview
What is Learning?
Classical Conditioning
Pavlov’s Experiments
Extending Pavlov’s Understanding
Pavlov’s Legacy
Operant Conditioning
Skinner’s Experiments
Extending Skinner’s Understanding
Skinner’s Legacy
Contrasting Classical & Operant Conditioning
Learning By Observation/Other Types of Learning
What is Learning?
Learning is a relatively permanent change in an
organism’s behavior, knowledge, capability, or
attitude that is acquired through experience and
cannot be attributed to illness, injury, maturation,
etc.
A change in neural function as a consequence of
experience
Learning is the process of acquiring knowledge or
skill through study, experience or teaching; it is a
process that depends on experience and leads to
long-term changes in behavior potential
Types of Learning
Non-associative learning: Learning in which there is
no connected stimulus
Habituation: The decline in the tendency to respond to nonchanging inconsequential stimuli
Sensitization: An increase in the tendency to respond to an
event that has been repeated
Habituation is affected by stress and gender
Stress reduces habituation (as does caffeine) (Beck et al.
’02)
Male rats were more affected by stress than female rats
Types of Learning
Associative Learning = Learning that requires
making new associations/connections
Learning connected two stimuli to each other
Learning to connect a response to its consequences
Learning new skills, facts, maps, etc
Psychomotor, cognitive, affective, etc.
A Unified Theory of Learning
Occam’s Razor / Principle of Parsimony / KISS
Philosophical foundation -- Associationism (Lock,
Hume, etc)
At birth, the human mind is a tabula rasa
All writing on the tabula is done by experience
Laws of Learning
Contiguity: events/ideas/sensations that occur together are
joined together
Frequency: the more often events/ideas/sensations occur
together, the stronger the link/association between them
Intensity: the stronger the intensity of feelings/effects
produced by events, the stronger the association between the
events
Ivan Pavlov
1849-1336
Russian physician /
neurophysiologist
Nobel Prize in 1904
Research on digestive
secretions
Pavlov’s Discovery
Pavlov’s Discovery
Before conditioning, food (Unconditioned Stimulus,
US) produces salivation (Unconditioned Response,
UR)
During conditioning, the neutral stimulus (tone) and
the US (food) are paired, resulting in salivation (UR)
After conditioning, the neutral stimulus (now
Conditioned Stimulus, CS) elicits salivation (now
Conditioned Response, CR)
Conditioning Application
Components of Classical
Conditioning: Acquisition
The initial stage of learning when a response is
established and gradually strengthened (the phase
in which a UCS comes to evoke a CR)
100
% CRs
80
60
40
20
0
1
2
3
4
5
6
Blocks of 10 Trials
7
8
9
Components of Classical
Conditioning: Extinction
After a rest period, an extinguished CR (salivation)
spontaneously recovers, but if the CS (tone) persists alone, the
CR becomes extinct again
Spontaneous Recovery: Refers to the reappearance, after a rest
period, of the extinguished CR
Components of Classical Conditioning:
Spontaneous Recovery
When the US (food) does not follow the CS (tone),
CR (salivation) begins to decrease and eventually to
become extinguished
Components of Classical Conditioning:
Spontaneous Recovery
Complete extinction of a response may be difficult
to achieve and may require many extinction trials
100
% CRs
80
60
40
20
0
1
3
5
7
9
11 13 15 17 19 21 23
Blocks of 10 Trials
Components of Classical Conditioning:
Generalization
Tendency to respond to stimuli
similar to the CS is called
generalization
Conditioned responses occur to
stimuli other than the CS used for
training
The more similar the second
stimulus is to the initial CS, the more
generalization will occur
Generalization is a critical feature of
learning because we rarely
encounter the exact same stimulus
twice
Components of Classical Conditioning:
Discrimination
Discrimination is the learned ability to distinguish between a
conditioned stimulus and other stimuli that do not signal an
unconditioned stimulus
Discrimination is the ability to distinguish between a CS and
other stimuli that do not signal a UCS
Individual Differences: Generalization
Implications of Classical Conditioning
Little Albert – Fear Conditioning
Watson & Rayner (1920) found a very loud noise made by striking a
steel bar with a hammer frightened little Albert, an 11-month old
infant
Albert was induced to play with a docile white lab rat. While so
engage, Watson struck the steel bar with the hammer immediately
behind the infant’s head. The authors report: “The infant jumped
violently, and fell forward, burying his head in the mattress … just
as his right hand touched the rat, the bar was struck again. Again
the infant jumped violently, fell forward and began to whimper.”
5 weeks later, when the rat was show to the infant, he immediately
began to cry … and to crawl away
When presented with a white rabbit, Albert feared it nearly as much
as the rat
Albert was less afraid of a dog or a fur coat
Abbert still feared these objects even after 2 months
Exogenous Factors that Impact
Classical Conditioning
Frequency of the CS – US pairing
The strength of the CR increases most in the early part of
the experiment
Consistency
Learning is weaker when conditioning and extinction trials
are mixed than when the CS and US are paired consistently
Consistent pairing makes the CS a better predictor of the
US
Kamin (1969) conditioned a CS1 – US pair. Then he
presented the CS1 together with an additional CS2, and
showed that even after many pairings, subjects showed no
CR to CS2
Blocking effect: Conditioning does not occur to a CS that
has no additional predictive value (Kamin 1969)
Exogenous Factors that Impact
Classical Conditioning
Timing
Forward conditioning, with a short interval between the offset of
the CS and the onset of the US, produces strong conditioning (but
see later) (but see taste aversion)
Belongingness (eg, taste belongs with food)
Conditioning is easier for CSs that seem to belong to the US
Strength of the US
Annau & Kamin (1961) varied the intensity of an electric shock
(US) paired with a tone (CS), and found that the magnitude of the
conditioned fear response dependent on the intensity of the shock
Endogenous Factors that Impact
Classical Conditioning
Autonomic Arousability
Some individuals are more reactive than others: Highly arousable
individuals will experience any particular US as more intense than
less arousable individuals
Classical Conditionability
CC refers to the ease with which an individual reaches a specified
criterion for learning. A twin study (Merrill et al. 1999) showed
conditionability of identical twins was more highly correlated than
the conditionability of fraternal twins
Evolutionary Factors that Impact
Classical Conditioning
Prepared Classical Conditioning
Evolution prepared us to be afraid of whatever
threatened our forebears (snakes, spiders, blood,
fire), and as a consequence, we condition
differently to these kinds of stimuli
Ohman et al (1976) used pictures of snakes,
spiders, houses and flowers as CSs and an electric
shock as the US. Conditioning was more rapid (and
more resistant to extinction) to snakes and spiders
than houses and flowers
Garcia did research on taste aversion & showed
that the duration between the CS and the US may
be long (hours), and conditioning may occur in a
single trial
John Garcia
Applications of Classical Conditioning
Learning by Observation
Children who witness their parent’s fear of a prepared stimulus
such as a snake or spider often develop the same fear (Mineka &
Cook ’93)
Finding suggests that mental representations can function as
unconditioned stimuli (scary stories can produce autonomic
responses)
Applications of Classical Conditioning
Drug Overdose Death
Conditioning can result in bodily reactions occurring in
anticipation of the consumption of particular substances
Drug Onset Cues … function as CSs, and they elicit compensatory
reactions (called drug tolerance) that diminish the effects of
taking a drug like morphine (this is why bigger and bigger doses
are required to bring about the same effect with extended use of
a drug)
What happens when DOCs are present but the drug/morphine is
not provided? The person becomes hypersensitive to pain
What happens when the drug/morphine is administered to an
addict but in the absence of DOCs? There is no conditioned
compensatory reaction, and the effect of the drug might be fatal
Operant/Instrumental Conditioning
A form of associative learning in which voluntary responses
come to be controlled by their consequences
Skinner used the terms operant or instrumental to describe
behavior that is strengthened by reinforcement
Both reflect the control that behavior has on getting
reinforcers from the environment
Operant: B/c behavior operates on the environment
Instrumental: B/c behavior is instrumental in producing
consequences
John B Watson:
Founder of Operant Conditioning
1878 - 1958
Psychology as a Behaviorist Views It"
(1913), he asserted that psychology
should restrict itself to the objective,
experimental study of the relations
between environmental events and
human behavior
Famous for Little Albert
Watson used classical conditioning
procedures to develop advertising
campaigns for a number of
organizations, including Maxwell House,
making the “coffee break” a North
American custom
Burrhus F Skinner:
Founder of Operant Conditioning
1904 – 1990
Behaviorism is the view that psychology
should be an objective science that
studies behaviour without making
reference to mental processes
Operant conditioning is the form of
learning in which rats and pigeons were
trained to press a lever (or peck a key)
in order to obtain a food reward using
the Skinner-Box
Edward L Thorndike:
Founder of Operant Conditioning
1874 – 1949
Law of effect: A given stimulus will elicit
a particular response if the response has
been regularly followed by satisfaction
or pleasure
The Stop-Action principle: The particular
form of a behavior that first led to
success is likely to persist
30
The Skinner Box
Operant Conditioning Phenomena
Learning
Occurs when a response is followed by consequences
Extinction
Occurs when we no longer follow the operant response
with a reinforcer/ment
Extinction does not involve punishment
Spontaneous Recovery
Generalization
Schedules of Reinforcement
Continuous Reinforcement: Reinforces the desired
response each time it occurs
Partial Reinforcement: Reinforces a response only
part of the time. Though this results in slower
acquisition in the beginning, it shows greater
resistance to extinction later
Schedules of Reinforcement
Fixed-ratio schedule: Reinforces a response only after a
specified number of responses (e.g., piecework pay)
Variable-ratio schedule: Reinforces a response after an
unpredictable number of responses. This is hard to
extinguish because of the unpredictability (e.g.,
behaviors like gambling, fishing)
Fixed-interval schedule: Reinforces a response only
after a specified time has elapsed (e.g., preparing for an
exam only when the exam draws close)
Variable-interval schedule: Reinforces a response at
unpredictable time intervals, which produces slow,
steady responses (e.g., pop quiz
Schedules of Reinforcement
Reinforcement & Punishment
Reinforcement: Any consequence that
increases the likelihood that the behavior
will occur again
Punishment: Any consequence that
decreases the likelihood that the behavior
will occur again
Reinforcement & Human Behavior
The percentage of times that a severely disturbed child said
“Please” when he wanted an object was increased dramatically by
reinforcing him for making a polite request. Reinforcement
produced similar improvements in saying “Thank you” and “You’re
welcome,” and the boy applied these terms in new situations as
well (Adapted from Matson et al., 1990).
Reinforcement & Human Behavior
The effect of delay of reinforcement. The learning score drops rapidly
when reward is delayed. Animals learning to press a bar in a Skinner
box showed no signs of learning if food reward followed a bar press by
38
more than 100 seconds (Perin, 1943).
Types of Reinforcement
A reinforcer/ment is any event that
strengthens the behavior it follows
Positive (plus) reinforcement
strengthens a response by presenting a
typically pleasurable stimulus after a
response (eg, getting candy, money, a
hug)
Negative (minus) reinforcement
strengthens a response by removing an
aversive stimulus after a response (eg,
turn off seatbelt noise, stop nagging)
Types of Reinforcement
Primary reinforcer/ment: An innately reinforcing stimulus like
food or drink
Conditioned reinforcer/ment: A learned reinforcer/ment that
gets its reinforcing power through association with the
primary reinforcer
Intrinsic reinforcement: Reinforcement that derives from the
activity itself, rather than from any consequences that might
follow
Extrinsic reinforcement: Reinforcement that derives from the
external consequences of performing the behavior
Types of Punishment
A punisher/ment is any event that weakens the behavior it
follows
Positive (plus) punishment weakens a response by presenting
an unpleasant/aversive stimulus after a response (eg, getting
scolded, shocked, fined)
Negative (minus) punishment weakens a response by
removing a desired stimulus after a response (eg, withhold TV
privileges)
Shaping/Learning to Pay Attention
Shaping is the operant conditioning procedure in which
reinforcers guide behavior towards the desired target behavior
through successive approximations
Shaping involves breaking down a complex behavior into a set
of steps that can be reinforced in sequence
Shaping can be used to establish complex behaviors (eg, to
teach a rat to pirouette)
Shaping has been used to teach social skills to autistic children
(Pollard 1992; Ingersoll & Carter, 2003)
Shaping Diction
A child who is learning to talk
points to her favorite doll and
says either “doll,” “duh,” or “dat”
when she wants it.
Day 1 shows the number of times
the child uses each word to ask
for the doll. At first, she uses all
three words interchangeably. To
hasten learning, her parents
decide to give her the doll only
when she names it correctly.
The child’s behavior shifts as
operant reinforcement is applied.
By Day 20, saying “doll” has
become the most probable
response.
Other Applications
Behavior modification is a method that uses
reinforcement, punishment and extinction as a
means of eliminating undesirable behaviors and/or
establishing desirable behaviors
Other Applications
Learned helplessness: When faced with a situation in
which no type of behavior produces desirable
consequences, we become helpless, and likely depressed
A rat raised in a cage where one side of the floor is periodically
electrified will quickly learn to escape to the other side
By contrast, a rat living in a cage where both side have been
electrified for a period of time will not try to escape later on when
only one side is electrified … the rat has learned to be helpless
Do people learn helplessness?
Lack of control and depression are frequently reported by victims of
persistent sexual abuse (Strube ’88)
Assumptions about Learning
Associationist principles are sufficient to account for
all learning
All stimuli are created equal
In CC, an organism can be taught a connection between any CS and
any US
In OC, an organism can be taught a connection between any
response and any reinforcer
All species learn the same way (the nature of the
organism does not matter)
Skinner: “Pigeon, rat, monkey, which is which? It doesn’t matter …
once you have allowed for differences in which they make contact
with the environment … what remains is astonishingly similar”
What stimuli are effective as CSs?
CSs?
Kamin (’69) and Rescorla & Wagner (‘72) asserted
that conditioning happens only when a subject’s
ability to predict the US is imperfect
The strength of conditioning depends on how much
improvement in prediction remains
Thus, without knowing a subject’s conditioning
history, it is impossible to know whether the
pairing of a CS and US will result in learning
Learning Changes more than Behavior
Evidence of cognitive processes during operant learning
comes from rats during a maze exploration in which they
navigate the maze without an obvious reward. Rats seem
to develop cognitive maps, or mental representations, of
the layout of the maze (environment).
Do we need an O between S + R?
Razran (’69) experiment with words as CS and tiny
squirt of lemon juice as the US. The UR was
salivation
Tested for generalization by changing the CS from
URN (used for conditioning) to either EARN or
VASE.
Found much more salivation to VASE than EARN
Only humans understand the semantic relation
between URN & VASE, and thus results argue that
the O is required between S + R
Types of Associative
Learning
Connecting two stimuli: Classical conditioning
Stimulus 1:
Lightning
+
Stimulus 2:
Thunder
Connecting a response to its consequences: Operant
conditioning
Response:
Push button
on vending
machine
+
Consequence:
Receive a candy
bar
Comparing classical &
operant conditioning
Classical Conditioning
Operant Conditioning
Nature of
Response
Reinforcement
Involuntary, reflex
Spontaneous,
voluntary
Occurs before
response (CS & UCS
are paired)
Occurs after
response
Role of Learner
Passive
Active
Nature of
Learning
Neutral S becomes CS Prob. responding is
by assoc. w. US
changed by its
effect
Comparing classical &
operant conditioning
1971
1948
Learning Objectives
ƒ Define learning, and identify two forms of learning.
ƒ Define classical conditioning and behaviorism, and describe the basic components of classical
conditioning.
ƒ Describe the timing requirements for the initial learning of a stimulus-response relationship.
ƒ Summarize the processes of extinction, spontaneous recovery, generalization, and
discrimination.
ƒ Discuss the survival value of generalization and discrimination.
ƒ Discuss the importance of cognitive processes in classical conditioning.
ƒ Describe some of the ways that biological predispositions can affect learning by classical
conditioning.
ƒ Summarize Pavlov’s contribution to our understanding of learning.
ƒ Describe some uses of classical conditioning to improve human health and well-being.
ƒ Identify the two major characteristics that distinguish classical conditioning from operant
conditioning.
ƒ State Thorndike’s law of effect, and explain its connection to Skinner’s research on operant
conditioning.
ƒ Describe the shaping procedure, and explain how it can increase our understanding of what
animals and babies can discriminate.
ƒ Compare positive and negative reinforcement, and give one example each of a primary
reinforcer, a conditioned reinforcer, an immediate reinforcer, and a delayed reinforcer.
ƒ Discuss the strengths and weaknesses of continuous and partial (intermittent) reinforcement
schedules, and identify four schedules of partial reinforcement.
Learning Objectives cnt
ƒ Discuss the ways negative punishment, positive punishment, and negative
reinforcement differ, and list some drawbacks of punishment as a behaviourcontrol technique.
ƒ Explain how latent learning and the effect of external rewards demonstrate that
cognitive processing is an important part of learning.
ƒ Explain how biological predispositions place limits on what can be achieved
through operant conditioning.
ƒ Describe the controversy over Skinner’s views of human Behaviour.
ƒ Describe some ways to apply operant conditioning principles at school, in sports,
at work, and at home.
ƒ Identify the major similarities and differences between classical and operant
conditioning.
ƒ Describe the process of observational learning, and explain the importance of the
discovery of mirror neurons.
ƒ Describe Bandura’s findings on what determines whether we will imitate a model.
ƒ Discuss the impact of prosocial modelling.
ƒ Explain why correlations cannot prove that watching violent TV causes violent
Behaviour, and cite some experimental evidence that helps demonstrate a cause55
effect link.
SA Questions
•
Define the following classical condition acronyms: US, UR, CS & CR
•
Define precisely what is (needs to be) learned in classical conditioning and
in operant conditioning.
•
What is meant by shaping?
•
What is the difference between shaping and operant conditioning?
•
What is spontaneous recovery?
•
At the level of the synapse, how might learning be represented?
•
What is latent learning?
•
What defines something as reinforcement or punishment?
•
Give a specific example of positive punishment and negative punishment.
•
Give a specific example of positive reinforcement and negative
reinforcement.
•
Which schedule(s) of reinforcement tend(s) to produce the highest level of
responding?