Extinction

How do animals “know” when a schedule is on extinction?

Remember

• Operant conditioning extinction differs from classical conditioning extinction

• Responds decreases to near zero for both

• Operant conditioning:– Transient increase– Extinction induced aggression

Partial Reinforcement Extinction Effect: PREE

• Extinction occurs at different rates depending on the schedule:– Continuous reinforcement: FAST extinction– Partial reinforcement schedules: SLOWER extinction– Variable schedules show slower extinction than fixed (rate or time)

schedules.

• PREE used to describe greater persistence in instrumental responding during extinction after partial (or intermittent) reinforcement training – Faster extinction after continuous reinforcement training.

• Partial reinforcement schedules show RESISTANCE TO EXTINCTION

Other Extinction Effects

• magnitude reinforcement extinction effect– Less persistence of instrumental behavior in extinction following

training with a large reinforcer – More persistance of responding with a small or moderate reinforcer. – Effect is most prominent with continuous reinforcement.

• overtraining extinction effect – Less persistence of instrumental behavior in extinction following

extensive training with reinforcement (overtraining) – Faster extinction following moderate levels of reinforcement

training. – Again, effect most prominent with continuous reinforcement

Other Extinction Effects

• reinstatement – Recovery of responding to an extinguished stimulus – produced by exposures to unconditioned stimulus or

reinforcer

• renewal – Recovery of excitatory responding to an extinguished

stimulus – produced by shift away from the contextual cues that

were present during extinction.

Why do we get these effects?

• Behavioral momentum and Sequential theory

• Trouble with discrimination

• Frustration

Behavioral Momentum

• Suggests that PREE occurs because the animal has a high momentum of responding and it is more difficult to stop this momentum

• Timberlake and Lucas 1985:– Ball bearing studies– Rolled ball bearing across cage; rats had to let it go past to receive reinforcer– Played with the ball bearing, slowing reinforcement– During extinction (ball bearing but no food): played with ball bearings MORE

• Does suggest that animals show strong patterns of behavior that may interfere and thus slow the extinction process

• But not a complete explanation

Discrimination and Frustration• Discrimination hypothesis:

– Mowrer and Jones 1945– In order for subjects’ behavior to change during extinction, the subject

must be able to discriminate the change in reinforcement contingencies

• With CRF: This is immediately noticeable

• With PRF: not immediately noticeable– More discriminative on fixed schedules– Less discriminative on variable schedules

• Evidence does not completely support this

Generalization Decrement Hypothesis

• Capaldi, 1966

• Generalization decrement: decreased responding observed in generalization test when test stimuli become less and less similar to training stimulus

• Responding during extinction is weak if the stimuli present during extinction are different from those during the reinforcement phase

• Responding during extinction is STRONG if the stimuli present during extinction are very similar to those during reinforcement phase.

Generalization Decrement Hypothesis

• Large generalization decrement when schedule moves from CRF to EXT– Subject never experienced situation in which some of its

responses are not reinforced– Not been taught to keep responding in absence of a reinforcer

• Small generalization decrement when schedule moves from PRF to EXT– Subject has experience in situation where some of its

responses are not reinforced– HAS been taught to keep responding in absence of a reinforcer

Sequential Theory

• sequential theory: memory of reward vs. non reward– Cognitive theory

• Fast extinction after CRF– Extinction occurs quickly because the instrumental response

has NOT been conditioned to the memory of nonreward

• Slow extinction during PREE – extinction is slowed after partial reinforcement because the

instrumental response becomes conditioned to the memory of nonreward.

Bottom Line• Rate of extinction is affected by:

– Discriminability of the situation– Previous experience with non-reinforced responding– Possibly, memory of non-reinforced responding

• Why frustration?– Not getting what expected

• Because of contingency between response and reinforcer:– Subject “controls” responding, and thus reward– During EXT: this contingency is disrupted– Subject becomes “frustrated” in that

• Tries other responses• Increases magnitude of responding• Increases intensity of responding• Pushed into fear/flight/fight sequence: aggression is elicited

Avoidance:

Avoidance Tests• Negative reinforcement = removing a stimulus to INCREASE a behavior

• Negative reinforcement =– escape: a response removes something– avoidance: a response prevents some event

• Procedure for studying negative reinforcement and avoidance: Discriminated avoidance:– a response CANCELS a shock– Organism is responding for food reinforcers– When light comes on, must press another lever to AVOID the shock

•

• if the response does not occur during the S+ the stimulus is followed by a shock• if the response does occur during the S+, the shock is cancelled

– thus: signal or sD for shock– if this were an escape: response could also occur DURING the shock to shut off shock

Two Avoidance Procedures:• Sidman Avoidance:

– the response POSTPONES or DELAYS the shock– thus: only temporary solution– must keep responding to keep delaying the shock– results in lots of responding– again: some signal may be used to signal when must respond

• Herrnstein and Hineline Procedure:– the response reduces the rate of the shock– note: note delay or cancel, just slows down rate of delivery– the response switches the schedule of shock to a lower rate– Note: cannot entirely AVOID shock in this procedure:

• once animal receives shock on lowered schedule, reverts back to original schedule• animal must respond again to switch schedule again

Characteristics of Avoidance Behavior

• extremely variable:– from subject to subject– from session to session with SAME subject– procedure to procedure

• choice of response is important– determines how quickly will learn contingency– how well learning is maintained

• 1-way vs 2-way shuttle avoidance tests:– 1-way shuttle: run to other end w/sD– 2-way shuttle: run to opposite end w/sD– rat will learn to run to other end of shuttle box when sD comes on to avoid shock

• difficult time learning 2-way shuttle avoidance

Characteristics of Avoidance Behavior

• Species specific Defense reactions:– behaviors which animal does naturally in time of

danger– includes: freezing, fleeing, fighting

• Why? – animal has innate behaviors does when avoiding

noxious stimulus- – can't make it go against its nature

Characteristics of Avoidance Behavior

• Negatively reinforced behavior is difficult to extinguish:– escape behaviors take long time to go away– e.g.: rat in 1-way shuttle still runs when light

comes on-even after hundreds of EXT trials

• BUT: will extinguish quickly if animal can detect change from conditioning to EXT situation

Negative Reinforcement in Humans

• most often "reinforcement" technique used in real world

• often used because is cheaper, easier, more natural

• produces "bad" side effects: avoidance responses to sD = boss, principal, spouse, etc.

Theories of Avoidance: Two Factor theory

• Two things happen during avoidance conditioning:– animal learns to fear S+ via class. cond'ing

• CS (light)---> US (shock): UR (fear)• animal learns to fear light via pairing with shock

– animal will then learn a response to AVOID shock and thus remove/lessen their fear

• thus: not getting shocked reduces fear that was signaled by the CS

• experimental evidence:– on initial training trials:– light/CS produces physiological symptoms of fear– escape response results in decrease in these physiological symptoms

• on later trials:– little or no evidence of physiological fear with CS presentation– suggests fear has been reduced/replaced by the escape response

• in sense: forms a negative feedback loop

Two Factor theory in Humans

• many ineffective and/or irrational fears– often involve avoidance responses due to original fear– maintained by decrease in fear– e.g., banging two sticks to keep the tigers away

• Symptoms of obsessive/compulsive disorders:– compulsions = repeated, stereotyped, ritualized actions

• individual feels compelled to engage in them

– obsessions = compulsive thoughts (no actual actions)– many, many examples of this– can begin to interfere in life

Problems with 2-factor theory:

• Signs of fear dissipate w/time:– as animal gets "better" at avoidance response– thus: no fear to be avoided

• the CS is not as important in avoidance learning as 2-factor theory states:

• animals can learn to avoid in a discriminated avoidance situation long before there is any sign that they are responding to/detecting the CS

Herrnstein and Hineline: Test of 2-factor theory

• Herrnstein and Hineline procedure: – not use any CS, but the animal still learns to lessen/avoid the shock

• Test of the theory: – two groups of rats used– Group 1: can turn off light, but still shock – Group 2: can turn off shock, light still on

• 2-factor theory would predict that Group 1 should respond more, because this would be cancelling the CS that produces fear

• results: group 2 responds much more accurately, faster

Alternative: One-Factor Theory

• responses occur whenever they reduce the rate at which aversive events occur

• when a CS is present: only providing information about the effectiveness of a response

• fear may be a by-product of avoidance training, but not crucial to learning/ maintaining an avoidance response

Evidence for One-Factor theory

• Almost postulating a "cognitive" theory of avoidance:

• Seligman and Jonston (1973) did postulate cognitive theory:– like Rescorla Wagner theory in that deals with predictability

• Basic premise:– learning occurs only when discrepancy between observation

and expectation – subjects' behavior will change in avoidance task whenever

there is a discrepancy between expectancy and observation

Evidence for One-Factor theory• Two important expectations in avoidance task:

– expectation about consequences of a response– .expectation about consequences of not responding

• Data support One-factor theory– on trial 1: no expectations– On trial 2 (and more): expectation about what will happen

• no shock will occur if response is made

– shock will occur if no response is made– animal prefers no shock to shock- so responds

• Contingency is what is important in avoidance, fear is by-product!

Evidence, con’t.

• as long as animal continues to respond- no shock– not know when extinction occurs- no sampling– only stop when learn situation has changed

• Thus: to EXT responding: – Must use response blocking or flooding:– present sD, but prevent R from occurring– thus animal learns that shock no longer comes– animal stops responding in presence of sD

Flooding

• To extinguish an inappropriate response: must make contact with "changed reinforcement or punishment" situation

• sometimes used as alternative to systematic desensitization

• flood with presentation of fear-provoking stimulus– Again, no actual consequence occurs– Continue presentations until the response is extinguished

• Problem: may "scare the patient to death"