Classical Conditioning

Learning: What does it mean to learn?

• Learning is the single largest area of Psychology second only to clinical psychology

I. Classical Conditioning – learning through association

• Philosophical roots: English Empiricists

• John Locke – Primary and Secondary Qualities

• David Hume – Reflection , Cause and Effect

Ideas

• Anything that stimulates the CNS

1. Pavlov and the conditioned reflex

• The procedure is what distinguishes classical conditioning from other modes of learning

Classical Conditioning in America was Stated by Watson and Rayner (1920)• Albert was set on a rug, held by Rayner

and presented with a fuzzy rabbit.• Watson slammed two sticks together

behind Albert as he reached for the animal.

• After several trials Albert began to cry when the rabbit was presented

Watson, Rayner and Little Albert

The Three Phase Process of Classical Conditioning

Habituation• Works at the neuron level to

organismic level.• Habituation decreases the responses

over time both for magnitude and frequency per unit time.

• The most basic level of learning. Requires no reinforcement.

Habituation (cont.)

• Habituation allows the organism to ignore irrelevant stimuli.

• Dishabituation is the stopping of habituation to an attended stimuli

Condition Stimulus (CS)

• A neutral stimulus, can be sound, light or internal craving.

Uncondition Stimulus (UCS)

• The natural stimulus that drives the CNS to elicit the reflex.

• In the vernacular of instrumental learning this hookup of the UCS-UCR is known as the reinforcement.

Uncondition response (UCR)

• The basic reflex that is become controlled by procedure.

Reinforcement vs Reward

• One reinforces a response!

• One rewards the animal!

Condition Response (CR)

• The response when driven by the Condition Stimulus

2. Major phenomena of classical

• Two types of “effective” procedures that lead the animal to predict up coming events.

Delay Conditioning: requires only recognition

Critical Measures: ½ mm movement is a response, Latency to onset of movement, Latency to peak of response.

3 Characteristics of Delay Conditioning

• The CS starts before the UCS

• There is a time period between when the CS in On and the start of the UCS – known as the Inter-Stimulus-Interval (ISI).

• Both the CS and the UCS co-terminate.

The association

• The explicit pairing of the CS with the UCS• (in eye-blink, if tone and then air-puff) sets

up the contingency that leads the animal to predict what is to come.

• This analysis of expectation was put forth by Rescorla.

Trace Conditioning: requires memory

3 Characteristics of Trace Conditioning

• The CS starts before the UCS

• The CS turns “OFF” before the UCS comes “ON”.

• The time period between the CS turns “Off” and the UCS comes “On” is the trace interval (the inter – stimulus – interval).

• The animal must remember to delay its response, and respond only at the end of the trace interval.

Backward Conditioning

Backward Conditioning (cont)

• UCS comes “ON” before the CS.• UCS goes “OFF” with “ON- set” of CS• Ineffective for producing a conditioned

response.

Simultaneous Conditioning: very hard to show.

Formal Classical Conditioning is a Three Stage Process

• Habituation – Paired Training - Extinction

Pavlov’s study

• Condition stimulus, CS, was the sound of a metronome (will become the condition reinforcer)

• The Uncondition Stimulus (UCS) was meat powder (the reinforcer).

• The uncondition response was drops of salivation.

• Condition response was salivation.

Trial - By - Trial Presentation

• Trials are presented singularly and continues until some criterion is met or a fixed number of trials completed.

Paired trials

• When both the CS and the UCS are presented in a fixed order and time frame

• (an explicitly paired trial).

CS Alone Trials

• Periodically only the CS is presented• Known as CS alone trials.• Measure the effectiveness of the CS to

drive the behavior

Statistics

• Mean and SD change in the timing or magnitude of the paired trials.

• Mean and SD of the CS alone trials

Results

• In the beginning trials the CS does not elicit the CR

• Across trials there is a change in the ability of the CS to drive the CR. The change increase as the trials progress.

• The CR looks like the UCR, but micro analysis of the two behaviors will show clear difference

Results of Explicit Pairing CS-UCS

• By the end of the trials, both for paired and CS alone trials, the CS is able to elicit the CR.

• Magnitude increases, time shortens or frequency changes for the behavior

How does one know that one has stimulus control?

• Use Extinction trials.

Present the trials in the manner of Habituation (but is not habituation)

• Repeated presentation of the CS alone will drive the changes that were learned during CS presentation to zero.

EXTINCTION

• Note at the beginning of day 2, the first response is larger than last response on day one. Called spontaneous recovery.

Generalization vs discrimination

• Generalization is the tendency to respond to like stimuli the same way.

• If a rabbit is trained on a 1200Hz tones, to a critiereon, his percent correct for a 800, or a 1600Hz tone will be less than the 1000Hz tones

• See next slide

Generalization gradient

Discrimination training

• The correct stimulus is explicitly paired with a given reinforcement (see Mauk and Ruiz slides 65- 71 below).

• Or two different responses are paired with two explicitly different stimuli.

The vast array of stimuli and condition responses

Eyeblink Studies

• First done by Ernest Hilgard in humans, dogs and monkeys 1928 – 1936).

• Modern Studies were started by Isidore Gormenzano

• A Model Animal – The Rabbit, its blink rate is 1 or 2 time a minute.

Eye lid Conditioning

• In the U.S. Ernest Hilgard studied eyelid conditioning in three major papers, 1929, 1932, 1936. He used dogs, monkeys and humans. He set the procedures for all neurosciences and their use of CC

Modern Studies started in 1964

Gormaenzano – modern study of eyelid conditioning

Mauk studies as representational of eyelid conditioning in the rabbit.

• Demonstrated, by brain removal studies in the rabbit, that classical conditioning could be mediated by the cerebellum alone.

Cerebellar brain circuit for mediating classical conditioning.

What Is The Behavior Measured

• A very sharp distinguishable criterion of what constitutes the movement of an eyelid.

Eyelid Movement Changed to an Electrical Potential

• An Stainless Steel Wire (0.007 in. by 0.018 cm) Extended From the suture loop in the eyelid to a phototransistor potentiometer.

Optional slide

• An infrared emitter is bounced off the eyelid. • The reflected beam passes through two small

Polaroid filters, one fixed and one operated by the eyelid closure.

• The two Polaroid filters are set so that infrared light passes through both filters to an infrared receiver when the eyelid is up.

The receiver turns the infrared light into volts, depending on the amount of infrared light received.

When the rabbit blinks its eye the wire is pulled and rotates the moveable Polaroid filter. This movement reduces the amount of light transmitted, lowering the voltage.

• The movement of the eyelid, closure (distance in mm), was calibrated to voltage drop by the potentiometer.

• A movement of ½ mm of eyelid was defined as an eyeblink.

CS

• Sine Waves of Various Frequencies presented at an intensity of 80dB (SPL)

UCS Airpuff

• UCS was calibrated to present to the eye and airpuff of 2 N/cm2 delivered to the cornea of the rabbit through, a 1 mm tuberculin syringe, positioned approximately 1 cm from the cornea.

Criterion Learning

• How Many Trials to Learn to a Fixed Criterion: Eight Correct Closures Out of Ten.

Fixed Trial Procedure

• Percent of Closures in X Number of Trials

Most Frequently Used Procedure

• Total of 108 Trials Divided in 12 Blocks

• First Trial of each block is a CS Alone Trial

• ACROSS 108 TRIALS: 12 CS ALONE TRIALS AND 12 BLOCKS OF PAIRED CS/UCS TRIALS

Critical Measures: ½ mm movement is a response, Latency to onset of movement, Latency to peak of response

What IS MEASURED

• NUMBER OF TRIALS IN WHICH AN EYEBLINK WAS MADE.

• LATENCY to ONSET: Time it takes from CS Onset to beginning of eye-blink (previously defined in terms of mm of movement).

Mauk & Ruiz

• The differential learning (conditioning) with two different ISIs.

Hypothesis:

• The rabbit can learn to discriminate between two different ISIs.

• The rabbit is learning to time its eye-blink to two different inter – stimulus – intervals.

• The rabbit is learning to time its behavior of eyelid closing!

Delay Conditioning: Two or more ISIs

• Manipulating the ISI is one of the independent variables.

The Independent Variables: CS1 and CS2 and the position of the US (UCS)

Note

• The US, in Mauk’s terms, in the above slides, must be manipulated to co-terminate with the CS. The UCS (air-puff) is always the in duration, 100ms. It occurs with the last 100 ms of the CS to co-terminate.

The Dependent Variable

• Getting the eye closed at the appropriate time

The Dependent Variable: The wiggly lines above CS1 and CS2

Acquisition of Conditioned Eyelid Closure (two different ISIs)

Latency To Onset of Eyelid Closure

Mauk & Ruiz: Six Different ISI to Six Different tones

Note the Difference in Behavior of the Eyelid to Different ISIs

Three Conditioned Eyelid Closures Elicited by Three Different ISI

Associated Tones

TRACE CONDITIOING

1. Acquisition of conditioned

• What is measured or counted• Number of blinks across trials for CS alone• Number of blinks across trials for paired

CS/UCS• Latency to Onset.

Neural Response

Berger et al

High-Order Conditioning

• One can use the CS as the UCS

CS USED AS A UCS

OVER SHADOWING

• The salience of one cue is greater than that of the other cue.

• The more salient cue overshadows the less salient cue. The less salient cue can not be used to predict the contingency.

TEST INDIVIDUAL CUE

TEST INDIVIDUAL CUE, LIGHT

BLOCKING

The behavior in Phase III

• In Blocking, when tested in Phase III, Group I does not demonstrate a CS to the sound. The light has control over the behavior in Phase II and the sound becomes blocked.

• When tested in Phase III, Group II shows CSs to both sound and light.

Test for Sound Group I

TEST GROUP II

Condition fear in a dog. Sound of the horn comes to signal the shock. The dog jumps over the divider.

• Panel 1 shock occurs with no cue. Dog jumps over barrier only when the shock appears. Non-cued shock increases fear and anxiety.

• Panel 2 a loud tone is presented before shock appears. A contigency is set up

The Condition Emotional Response - CER

• The sequence described above is how emotional responses get tied to external cues.

• The reduction of anxiety is a positive state of affairs for the animal, i.e., a positive reward.

• In the above dog case the dog avoids the negative state off affairs, fear, leading to anxiety.

• between the shock and the tone. The tone comes to predict the shock. Anxiety is high before tone is on.

• Panel 2 the dog comes to jump, before the shock when it hears the tone. Anxiety starts to drop as the dog starts to jump. Note the shock has not appeared.

• Panel 3 Dog is jumping, shock appears, anxiety goes down.

• Drug habits in humans leads to the paraphernalia of the habit to become condition stimuli for the high response, coupled with avoidance behavior of the withdrawal symptoms. The withdrawal symptoms leading to anxiety coupled to fear.

What is learned in Classical Conditioning?

• The animal learns an “if – then” contingency relationship between the CS and the UCS.

• The CS increases the probability that the UCS will follow.

• The animal has increasing predictability that the UCS will follow the CS, thus gaining control off the situation!