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
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
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
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-
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
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
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
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