Classical Conditioning

Ivan Pavlov

• Medical physiologist

• Digestion

• Reflexes

• Fistula

en.wikipedia.org/wiki/File:Ivan_Pavlov_(Nobel).pngen.wikipedia.org/wiki/File:One_of_Pavlov%27s_dogs.jpg

Stimuli & Responses

• Unconditional– Stimuli and responses whose properties

are not dependent upon prior training

• Conditional (i.e., “dependent”)– Stimuli and responses whose properties

occur only after training

• US, UR, CS, CR

Classical Learning Features

• Reflex

• Subject’s behaviour does not cause delivery of US

• Association of stimuli

Temporal ArrangementShort Delay

Long Delay

Trace

Simultaneous

Backwards

Terms

• Conditioning trial– Each CS-US pairing

• Intertrial interval– Time from end of one trial to start of next

trial

• Inter stimulus interval– Time from the start of the first stimulus in

pair to second stimulus in trial

Conditioning trial

Interstimulus interval

Intertrialinterval

CS

US

Measuring Learning

• Test (probe) trial– Present CS by itself (no US)

• Magnitude– How much CR occurs

• Probability– How often CS produces CR

• Latency– How soon CR occurs after CS

Pseudoconditioning

• Increase in response due to just the US

• Sensitization

Controls

• Random control– Exp. Gr.: CS-US pairings– Control Gr.: same number of CS & US, but

randomized

• Explicitly unpaired control– Exp. Gr.: CS-US pairings– Control Gr.: same number of CS & US, but

presented far enough apart (even separate sessions) to prevent association

CS Types

• Excitatory CS (CS+)– CS predicts the occurrence of US– Activates behaviour related to US

• Inhibitory CS (CS-)– CS predicts the non-occurrence of US– Suppresses behaviour related to US

Inhibitory Conditioning

• Why predict non-event?

• Unpredictable aversive events more stressful

• Craske et al. (1995) measured general anxiety in subjects with panic disorder– Predictable and unpredictable attacks– Before and after anxiety ratings

Results

Before After

Gen

eral

Anx

iety

Predictable

Unpredictable

• Similar anxiety before• Post attack anxiety significantly lower if

attack predictable and higher if attack unpredictable

• Ability to predict aversive event also allows prediction of lack of aversive event

• Application: stress management techniques– Can’t eliminate all stressors– Introduce periods of predictable “safety”– Reduces overall stress

Producing CS-

• Can produce CS- for either appetitive or aversive US

• Most research done with aversives• Inhibitory conditioning (and inhibitory

control of behaviour) only if there is also an excitatory context for US delivery– Can’t have CS- without CS+– But, can have CS+ without CS-

Pavlov’s Protocol

• Randomize trial type presentation

CS+

CS-

US

Trial Type A Trial Type B

Negative Contingency Protocol

• Context cues serve as CS+

CS-

US

Testing for CS-

• CS- produces absence of CR

• No CR– You’ve produced CS-– Haven’t learned anything

• How to measure nothing…

Techniques• Bidirectional response

– Utilizes opposing responses– Do one with CS+, opposite with CS-

• Summation test– Measure CR with CS+– Compound stimulus of CS+ & CS-; measure CR

• Retardation of acquisition– Trained CS- and novel stimulus; pair both with

novel US for same number of trials– Measure CR for both– Prior learning of CS- inhibits learning new

association

Backwards Conditioning

• Inconsistent results across studies– Little learning at all, CS-, CS+

• Keith-Lucas & Guttman (1975)– Backward conditioning and biological

plausibility– Predator attacks prey

• Antelope grazing• Lion attacks• Antelope clawed, but escapes• Pain (US); proceeds sight of lion (CS)

Experimental Procedure

• Rats fed sugar pellets

• Give one-time electric shock (US)

• Lights go out– 1, 5, 10, or 40 seconds

• Toy hedgehog added (CS)

• Observe rat one day later

Model

• Sugar pellets = grazing

• Shock = pain of attack

• Hedgehog = lion

Control Groups

• Saw hedgehog, but no shock

• Shocked, but didn’t see hedgehog

Results

• Backward conditioning not seen in controls

• In 1, 5, and 10 sec delay groups, got backward conditioning– Avoid hedgehog– Don’t eat much when hedgehog present

• Fear induced by hedgehog is CR

Conclusion

• Biologically relevant CSs can cause backward conditioning

Emotional Conditioning

• Wide range of emotional responses

• Emotions universal

• Positive and negative

• Emotional response to stimulus reflexive

• Conditioned Emotional Responses (CERs)

John Broadus Watson

• Hard-line Behaviorism

• British Empiricism (nurture over nature)

• Early work with rats

• Shift to infant research

• Opposed Introspectionism and Freudian theories

Conditioning of Fear

• Watson & Raynor (1920)

• Albert B.– Mother a wet nurse at Harriet Lane Home

(attached to Johns Hopkins University)– Albert first assessed at about 8 months– Emotionally stable, healthy

Method• Present white rat

– No fear

• Present white rat and bang metal bar– Produces CER of fear, avoidance,

withdrawl

• US = noise, UR = startle • CS = rat CR = fear• CER generalizes to other furry objects• Video

• Study went for several months

• Intended to reverse CER conditioning, but Albert B’s mother ended her job at hospital

• Research led directly to Mary Cover-Jones’ counter-conditioning with Peter

What Happened to Albert

• Beck, Levinson & Irons (2009)• Historical detective work• Albert B.’s mother probably Arvilla Irons

Merritte– Douglas Merritte, born 9 March 1919

• Arvilla Merritte left Johns Hopkins• Worked as assistant for ill wife of farmer• Douglas Merritte died 10 May 1925, probably

from meningitis

Name

• Why Albert B.?– Ethical concerns with confidentiality not

firmly established– Watson may have played “name games”– His sons William and James– His name from John Albert Broadus,

Baptist minister… Albert B.

What Happened to Watson• Affair with Rosalie Raynor, his grad student• Divorce, fired, resigned as president of APA• Worked for J. Walter Thompson advertising

agency; vice-president within two years• Ponds cold ream, Maxwell House coffee• Published books and articles on childcare

– Psychological care of infant and child (1928)– Criticized by many modern child experts/advocates,

but not any more extreme than other childcare texts of the time

– Strongly advocated against spanking and corporal punishment

Nonhuman Studies of Fear

• Typically use shock as US• Rats freeze• SSDS• Conditioned suppression ratio• Train operant response; train CS+ for

aversive US, test suppression of operant response in presence and absence of CS

• Suppression video

Suppression Ratio

• 0 if behaviour entirely suppressed

• 0.5 if no suppression

Suppression Ratio = CS Responding

CS Responding + pre-CS Responding

Pre-CS CS Calculation S.R.

25 25 25/(25+25)=25/50 0.5

25 0 0/(0+25)=0/25 0

25 15 15/(15+25)=15/40 0.375

Sign Tracking

• Also now called autoshaping (Brown & Jenkins (1968)

• Response not required• US often food• Stimulus (CS) indicates US availability• Subject “tracks” the sign more and more• CS takes on properties of US• Pigeon autoshaping• Longbox autoshaping

Biological Predispositions

Timberlake & Grant (1975)

Burns & Domjan (2000)

Taste Aversion

• US = stimulus producing illness

• UR = illness, nausea, etc.

• CS = (generally) novel taste

• CR = nausea

• Long delay or trace conditioning

Theory of Interest

• Contiguity

• Equipotentiality Premise– Pavlov– Doesn’t matter what you use as CS– Any stimulus can be conditioned to any US

Initial Studies

• Garcia & Koelling (1966)

• Garcia, Ervin & Koelling (1966)

• Difficulty getting published

• Finally, accepted in Psychonomic Science

Results

• US = poison, CS = novel flavour

• Delay between CS and US 5 - 22 minutes produced very strong CR

• Weaker, but significant CR (avoidance of flavour) with up to 24 hour ISI!

• Violation of contiguity

Results

• Violation of equipotentiality• Some CS-US combinations more easily

learned• Biological predispositions

Wat

er C

onsu

med

Pre-cond. Post-cond.

Wat

er C

onsu

med

Pre-cond. Post-cond.

US=X-ray US=shock

Flavoured water

“Bright-noisy water

Scientific Pardigms

• If evidence contradicts fundamental premise…reject the evidence

• But… sometimes unexpected results are correct

Eye Blink

• US = air puff UR = blink

• CS = noise, light, vibration, etc. CR = blink

• Straight-forward classical conditioning

• Vehicle for examining neurobiology of learning and memory

Brain CircuitryCerebral cortex

Interpositus nucleus

Red nucleus

Cranial motor nuclei

Inferior olive

Trigeminalnucleus

Reticularformation

Pontinenuclei

Auditory nuclei

Cornealair puff US

Tone CS

EyeblinkUR & CR

CR

CR

CS

CS US

US

reflexpathsUR

Climbingfibres

Mossyfibres

Eyeblink Exercise

• We can do science to it!

• Yes, real science with nothing more than a turkey baster, a pencil, and paper.