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Associative Learning
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Challenge Questions• You are a psychologist treating a patient who is
addicted to smoking. Explain how you would treat the patient’s addiction.
• You are a therapist who has a patient with a fear of spiders. Their spouse loves the outdoors and this fear interfering with their marriage. How would you treat this patient?
• You are a coach of a football team and your quarterback is throwing too many incomplete passes. Explain how you would use learning theory to help his game.
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The Smoker’s Brain
• The smoker would care.• Nicotine influences the
levels of certain neurotransmitters.
• Nicotine can prevent the break down of dopamine, increasing its presence in brain neurons.
• This causes the pleasurable effects of smoking.
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The Phobic’s Brain
• The amygdala is activated by a relatively harmless stimulus.
• This creates a fear response.
• In a patient with a phobia inhibition by the prefrontal cortex does not occur.
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The Quarterback’s Brain
• The cerebellum coordinates and controls movement.
• Despite its small volume, it contains nearly half the cells in the entire brain.
• Cerebellar damage impairs the timing of one’s movements.
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Outside of the Black Box
• Learning is something that can be observed without observing the brain directly.
• In fact, behavioral psychologists treat the nervous system as a “black box” and focus mainly on relationships among observable stimuli and behaviors.
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ASSOCIATIVE LEARNING
Classical conditioning: learning associations between objects.
learning associations between objects.
Operant conditioning: learning that, in a particular situation, a certain response leads to a certain outcome.
There are two types of associative learning:
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Classical Conditioning
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Ivan Pavlov
• Classical Conditioning was discovered by the work of Ivan Pavlov.
• He was studying digestive physiology for which he won the Noble Prize.
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CLASSICAL CONDITIONINGAn object or an event that you sense is referred to as a stimulus
We distinguish two types of stimuli and responses:
• Unconditioned stimulus (US) A stimulus that naturally evokes a response or reflex called the Unconditioned Response (UR)
• Conditioned stimulus (CS) A stimulus that does not naturally evoke a response. However, it can acquire the ability to elicit the response, called the Conditioned Response (CR).
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PAVLOV’S EXPERIMENT
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Stimulus Generalization
• Stimulus Generalization occurs when animals respond more to stimuli that are similar to the original than to those which are different.
Example: The dog in Pavlov’s experiment would also salivate to tones of similar frequencies to the original.
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Stimulus Generalization Gone Wrong!• In 1920, little Albert, an eleventh month old orphan,
learned to fear a rabbit.
• Eventually all white fuzzy objects caused the same fear in little Albert even though they were not paired with the US (loud sound).
and
But if you present simultaneously
many times, then
Initially, the soundcauses fear…
But not the rabbit
… the rabbit also causes fear!
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Stimulus Discrimination
• Stimulus Discrimination occurs when animals are conditioned to respond to one specific CS and not others.
Example: Only a tone of a specific frequency is followed by food. Other tone frequencies are presented without food. As a result, the dog only salivates after the tone of a specific frequency.
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The Sequence of Events
• Acquisition: the gradual increase in the strength of a response that occurs with the pairing of a CS with a US.
• Extinction: occurs when the CS is presented without the US causing a decrease in the strength of the response.
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Classical or Pavlovian Conditioning
Strengthof CR
Time/Trials
Acquisition(CS+UCS)
Extinction(CS alone)
Extinction(CS alone)
Spontaneousrecovery ofCR
Graph from Myers 6th Ed.
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Operant Conditioning
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OPERANT CONDITIONING
The frequency of a behavior is influenced by the presence or absence of a rewarding or aversive event after the expression of this behavior
This theory is called Behaviorism
B.F. Skinner developed the Skinner box to study this type of learning in pigeons. The pigeons learned to press levers to receive a reward!
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Sequence of Events
• Acquisition: The animal’s response produces a reinforcer.
Example: A rat presses a bar that produces food. The rat will begin to press the bar more frequently.
• Extinction: The animal’s response no longer produces a reinforcer.
Example: A rat presses a bar but it no longer produces food. The rat will press the bar less frequently.
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Schedules of Reinforcement
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Examples of SchedulesFixed Ratio Schedule: A rat is given food for pressing a lever every 3 times.
Fixed Interval Schedule: A rat is given food for pressing a lever after 1 minute has elapsed.
Variable Ratio Schedule: A rat is given food for pressing a lever an average of 3 times.
Variable Interval Schedule: A rat is given food for pressing a lever after an average of
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Associative LearningADAPTIVE TIMING:
ADVANCED MODELINGCLASSROOM PRESENTATION
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WHAT NEEDS TO BE MODELED?
Anatomy Neurophysiology
A Complete Circuit!
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EXPERIMENTAL PROTOCOL
US: air puff
Learning phase: for a selected number of trials, the sound is presented before the air puff (in delay or trace
conditioning)
Testing phase: the sound alone is presented to test for CR
CS: sound
UR, CR: nictitating membrane extension
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TIMING IS EVERYTHING!
The eye blink is a very transient response: must be made just prior to the air puff.
If it is done too late, the eye is not protected when the air puff occurs.
If it is done too early, the eye is not protected either since the blink ends too early!
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EXPLAINING ADAPTIVE TIMING
How does the brain learn to execute the right response at the right time?
We need to consider the neural circuits involved in producing the eye blink response
The critical structure is the cerebellum
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THE BIG ISSUES
The brain must have a way to keep track of time. It must have some kind of internal clock
Learning may take place over many trials: learning occurs at a certain rate which can vary
Both aspects can be studied through mathematical models
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INTERNAL CLOCK IN THE CEREBELLUM
Through a complex chemical process, some cells in the cerebellum can represent how much time has elapsed since a conditioned stimulus (CS) was presented
The same cells can also learn to associate the unconditioned stimulus (US) with the CS
Thus, these cells learn to time conditioned responses (CR)
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ANATOMY OF A NEURON
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CEREBELLAR CIRCUIT
The circuitry involved in adaptive timing involves a several types of cells connected in very specific circuits
The diagram illustrates that different circuits or pathways support specific sensory input (US, CS) and motor output (CR)
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US PATHWAY
The US signal due to the air puff to the eye travels in the pathway outlined in red
First it is relayed to the inferior olivary cell
Then it is communicated the Purkinje cell through climbing fibers
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CS PATHWAY
The CS signal due to the tone travels in the pathway outlined in green
First it is relayed to the pontine nuclei
Then it is sent to granule cells through mossy fibers
Finally, it reaches Purkinje cells via parallel fibers
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CR PATHWAY
Purkinje cells influence cells in the interpositus nuclei, which directly control the expression of the CR through a series of projections ending at the facial nucleus
The facial nucleus emits the appropriate motor response to cause the blink
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The Central Circuitry Involved in Adaptive Timing
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Required Parameters for the Cerebellar Model of Adaptive Timing of Eye Blinks
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING: INQUIRY THROUGH SOFTWARE 1
Model 1: Simple user interface for virtual experiments (for less experienced students)
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING: INQUIRY THROUGH SOFTWARE 1
Model 1: Simple user interface for virtual experiments (for less experienced students)
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING: INQUIRY THROUGH SOFTWARE 2
Model 2: More complex interface for more experienced users
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A NEURAL NETWORK MODEL OF ADAPTIVE TIMING: INQUIRY THROUGH SOFTWARE 3
Model 3: Most functionality for most experienced users