Negative Reinforcement - Escape

Negative reinforcement - Avoidance

Avoidance: Experimental Paradigm

The shuttle box

Light = CS

Light Shock

Shuttling stops shock

Two-Process Theory of Avoidance

Light Shock ( = Pavlovian Conditioning)

-Light elicits fear

Shuttling Reduction of Fear (= negative reinforcement)

Now, what happens with continued training?

Learned Helplessness Paradigm“Triadic” Design

Group A: Escapable Shock

Group B: Yoked Inescapable Shock

Group C: Exposure to apparatus only

Phase 1 Phase 2

Escape/Avoidance training

(For Group A shock can be terminated by rotating a wheel.)

Phase 2 Results

Inescapable shock

Inescapable shock

Possible Explanations• Learned Helplessness: Organisms learn that their

behavior is ineffectual

• Poverty of activity: inescapable shock reduces the variability in behavior that is so crucial for operant conditioning

• Inattention: animals stop attending to their own behavior

LH in the Spinal Cord

• Recall: many reflexes are mediated within the spinal cord.

• Operant conditioning can occur within SC (escape/avoidance of leg shock after SC transection)

• Grau: Experience with inescapable legshock will prevent subsequent avoidance learning.

LH in Humans

LH produced by…

insoluble logic problems

living in a crowded dorm

LH in the Spinal Cord

• Recall: many reflexes are mediated within the spinal cord.

• Operant conditioning can occur within SC (escape/avoidance of leg shock after SC transection)

• Grau: Experience with inescapable legshock will prevent subsequent avoidance learning.

Extinction

ExtinctionSession 1 Session 2 Session 3

Spontaneous recovery occurs as a function of time

8-day break

no breakno CS

Theories of Extinction

• Forgetting?

• Associative loss? (= “reverse acquisition”)

Extinction Associative Loss“Renewal”

Train Extinguish Test

Tone Shock

Context A

Context B

Tone -

Tone -

Tone: CRTone: CR

Bouton & King (1983)

In contrast, acquisition is not context-specific

Train Test

Tone Shock

Context A

Context B

Tone: CR

Tone: CR

Extinction Associative Loss“Reinstatement”

Train Extinguish Reinstatement Test

ToneShock Tone -Shock alone

--

Tone: CR

Tone: CR

Extinction Associative LossPost-extinction sensitivity to outcome devaluation

Rescorla 1996

So, what is learned in extinction?An inhibitory SR association?

S R

Context

Inhibitory SR Associations Theory

• In extinction, the context effectively becomes a conditioned inhibitor.

• Why? Just like in normal CI, there is the violation of expectations of reinforcement

• But is this true?

Inhibitory SR Associations

• Summation test

• Retardation test

Does extinction produce them?

Train Ext Test

A+/B+ A- Test: AB

Train Ext Train

A+ A- AB+

Does A inhibit responding to B?

Does A inhibit acquisition to B?

So, what is learned in extinction?An inhibitory SR association?

S R

Context

Paradoxical Effects of Reward

• Overtraining extinction effect: more training leads to faster extinction

• Reinforcement magnitude effect: Big rewards lead to faster extinction

• And, of course, the partial reinforcement extinction effect (PREE)

Paradoxical effects of reward: Why?

• Frustration hypothesis (Amsel): animals learn to make response as a reaction to nonreward.

• Discrimination hypothesis: Nonreinforcement is easier to detect after CRF than PRF.

• Sequential theory (Capaldi): The memory of nonreinforcement becomes a cue that elicits responding.