Learning

Electrical Activity of the Neuron

Learning is a change in behavior as a result of past experience

Even though our principal interest is in how humans learn, you’ll notice that a great deal of learning research

is conducted using animal subjects instead

• Less Complexity

•Greater Control Over Variables

•Generality of Principles

Classical Conditioning (Pavlovian Conditioning)

Electrical Activity of the Neuron

Ivan Pavlov (1849 – 1936) Famous Russian Physiologist who won a Nobel Prize in 1904 for his work on the biochemical analysis of digestive secretions of the stomach

His later notoriety stems from the widely-known studies he performed on conditioning of the salivary response

But his actual discovery of conditioned reflexes occurred in a different context much earlier

Classical Conditioning (Pavlovian Conditioning)

Electrical Activity of the Neuron

Procedure : 1. Dog transported from colony room to test cubicle and

chained to a hitch post

2. Food was prepared on a table 10’ away from subject

3. Dog was fed and 10 minute waiting period allowed

4. Fistula clamp was opened to allow for collection of digestive secretions which occurred in response to the arrival of food in the stomach

A mistake in the procedure leads to a discovery!

The fistula clamp was not closed properly allowing for leakage. Secretions were observed taking place prior to feeding. Pavlov termed these “Psychic Secretions”

Classical Conditioning (Pavlovian Conditioning)

Electrical Activity of the Neuron

To more conveniently study “psychic secretions”, a new procedure was devised involving the salivary reflex

The Classical Conditioning Paradigm

Stage 1 (Before Conditioning)

US (UCS) - Unconditioned Stimulus

A stimulus which reliably and without an prior experience reflexively causes a response to occur (the Unconditioned Response – UCR or UR)

UCS UCR (Food) (Salivation)

Some of the Most Frequently Studied Classically Conditioned Responses

dry food or acid in mouth salivation

electric shock electrodermal activity (GSR)

electric shock or loud noise cardiac acceleration

electric shock or loud noise sudden respiratory inspiration

change in illuminationelectric shock

pupillary reflex

food in viscera gastro-intestinal secretion

insulin injection hypoglycemia

Autonomic Activity

Some of the Most Frequently Studied Classically Conditioned Responses

Skeletal Activitynipple on cheek or lips rooting, sucking

loud noiseairpuff to corneasuborbital electric shockblow to the eye

eyeblink or nictitating membrane response

food in the mouth mastication

electric shockheatpin prick

flexion, limb withdrawal

Some of the Most Frequently Studied Classically Conditioned Responses

Skeletal Activitynipple on cheek or lips rooting, sucking

loud noiseairpuff to corneasuborbital electric shockblow to the eye

eyeblink or nictitating membrane response

food in the mouth mastication

electric shockheatpin prick

flexion, limb withdrawal

Brain Activity

illumination EEG occipital alpha rhythm

The Classical Conditioning Paradigm

Stage 1 (Before Conditioning)

A neutral stimulus – that is, one that does not initially cause the UCR to occur. This stimulus might be referred to as the to-be-conditioned stimulus (CS)

UCS UCR (Food) (Salivation)

CS(Bell)

The Classical Conditioning Paradigm

Stage 2 (During Conditioning)

During conditioning we repeatedly pair, close together in time, the originally neutral stimulus with the UCS

UCS UCR (Food) (Salivation)

CS(Bell)

Temporal Contiguity is the key facet of combining the stimuli for conditioning to in fact occur

The Classical Conditioning Paradigm

Stage 3 (After Conditioning)

After conditioning we present the originally neutral stimulus by itself and observe a conditioned response (CR)

CR (Food) (Salivation)

CS(Bell)

We refer to the process that has occurred as “Acquisition” since a new response is being acquired to the originally

neutral stimulus

The CR and the UCR are not identical responses. The CR is always a fractional component of the UCR.

The Fractional Anticipatory Nature of Classical Conditioning

Classical Conditioning represents a learned connection between environmental events that are likely to happen together.

We become more effective in our response to events if we prepare for them before they occur.

A dog can more efficiently eat and swallow food if he salivates in anticipation of feeding.

Example of driving away in your car after class is over.

Preparing your keys in advance is anticipatory of a situation that you are soon to encounter. The response is fractional as you can not insert and turn the key until the lock is encountered.

Organisms that prepare for events before they occur are likely to be more effective in their response.

Stages of Learning

Stimulus Generalization

Stimulus Generalization Decrement The degree of response to test stimulus is gradually reduced as stimulus differs more and more from the original

Discrimination

Discrimination is said to occur when the subject responds differently in the presence of one stimulus versus another.

Conditioned Emotional ResponseOriginally neutral stimuli can take on aversive characteristics as a result of being paired with

primary aversive stimuli. Watson and Raynor (1920) explored the development of a conditioned emotional response in the infant “Little Albert”

Instrumental Conditioning

This form of learning is called “Instrumental” because the subject desires his environment to change in some way. But

in order for this to occur, his own behavior will be instrumental in bringing about the desired change.

For example, I’d like my environment to include a hot steaming pizza in front of me right now.

But for this to become true, I must act in a certain way. My behavior will be instrumental in causing this to occur.

An alternate terminology for this for of learning is to call it “Operant Conditioning” because the behavior operates

upon the environment, changing it in some way.

Instrumental Conditioning Distinguished From Classical Conditioning

Classical conditioning involves an association between stimuli. The subject comes to learn that one stimulus is contingent (dependent) upon the occurrence of another.

E.G., Pavlov’s Dogs learned that food delivery was contingent upon the ringing of the bell

Instrumental conditioning involves an association between a response and a stimulus. The subject comes to

learn that a stimulus is contingent (dependent) upon the emission of a response.

E.G., A dog learns that a doggy treat is contingent upon posturing into the “begging” position

Instrumental Conditioning

Instrumental Conditioning was first defined and studied by E. L. Thorndike

The Law of Effect (Thorndike)

The likelihood and strength of a behavior are determined by the consequences it produces.

If a behavior is followed by a positive state of affairs, the response becomes stronger (reward training).

If a behavior is followed by a negative state of affairs, the response becomes weaker (punishment).

Such negative stimuli are referred to as being “Aversive”.

Administration of negative and positive stimuli creates four distinct Instrumental Conditioning Training Paradigms.

The term “Reinforcement” is used to refer to any stimulus which has the capability to strengthen behavior

The Asymmetrical Law of Effect

The general belief amongst psychologists that reward and punishment differ significantly in their effectiveness in

modifying behavior

Punishment suppresses behavior but its effects are diffuse (Suppression affects all behaviors, not just

the punished behavior).

Punishment produces disruptive negative emotionality.

Punished behaviors show a large spontaneous recovery.

Instrumental Conditioning Paradigms

Nature of the Stimulus

Positive Negative

Target Response Causes Application

of the Stimulus

Target Response Prevents or Causes

Removal of the Stimulus

Positive Reinforcement

(Appetitive Conditioning)

Negative Reinforcement

(Escape or Avoidance)

Punishment

(Aversive Conditioning)

Omission

The Cumulative Response Record

Variables Influencing Instrumental Conditioning

Amount of Reinforced Practice                       

Learning Curve

Negatively Accelerated

Asymptote

Variables Influencing Instrumental Conditioning

Amount of Reinforced PracticeAmount of Reinforcement                       

Large Magnitude of Reward

Small Magnitude of

Reward

Variables Influencing Instrumental Conditioning

Amount of Reinforced PracticeAmount of ReinforcementQuality of RewardDelay of RewardReinforcement Schedule                       

Schedules of Reinforcement

CRF (Continuous Reinforcement) – Each response is followed by reward.

p (reward) = 1.0

EXT (Extinction) – Each response followed by no reward

p (reward) = 0.0

PR (Partial Reward) – Responses are followed by reward with a probability greater than 0 but less than 1.

50% PR schedule would mean subjects would be reinforced on a random ½ of their trials

The Partial Reinforcement Effect (PRE)

CRF

PR