Classical Conditioning Chapter 3 Classical Conditioning

Ivan Petrovich Pavlov (1849-1936) Classical (Pavlovian) conditioning Medical physiologist Digestion Human/animal differences Conditioned reflexes en.wikipedia.org/wiki/File:Ivan_Pavlov_(Nobel).png en.wikipedia.org/wiki/File:One_of_Pavlov%27s_dogs.jpg

Terminology Unconditional stimulus (US) Unconditional response (UR) Stimulus that elicits the innate reflex (e.g., food) Unconditional response (UR) Reflex action that occurs in response to US (e.g., salivation) Conditional stimulus (CS) Any stimulus that doesn’t originally elicit the UR (e.g., bell) Conditional response (CR) The action elicited by the CS (e.g., salivation)

Conditioning and Awareness Awareness of conditioning not required for learning

Innate US-UR is an innate stimulus-behaviour “Reflex” Hardwired Stereotypic pattern of behaviour

Example: Bell and Food CS US UR CR Later Trials CS US UR First Few Trials Time CS = bell US = food UR = salivation CR = salivation

Processes Acquisition Extinction Acquiring a CR E.g., pair CS with US Reduce/eliminate a CR E.g., present CS without US

Measuring Conditioning Sometimes difficult to measure CR e.g., if CS & US close together, CR & UR can overlap Test trial (probe trial) Give CS alone Intensity Does CR intensity increase with experience?

Example: Eyeblink Conditioning CS (tone) US (airpuff) Airpuff on eye Blink UR vs. CR eyeblinks UR blink faster than CR blink CR (blink) UR (blink)

Example: Taste Aversion Very strong Very persistent Usually conditioned after one presentation Experiment Rats fed novel food (CS) Injected with lithium chloride (US) Choice: novel food or regular food Chose regular food

Higher-Order Conditioning CSs and USs can be associated (First-order) CSs can be associated with other CSs Second-order conditioning

First-Order Conditioning tone (CS1) food (US) salivation (CR)

Second-Order Conditioning light (CS2) tone (CS1) salivation (CR) Risk of extinction? salivation (CR) tone (CS1) food (US)

CS+ and CS- CS+ (excitatory CS) CS- (inhibitory CS) CS predicts occurrence of US Activates behaviour related to US CS- (inhibitory CS) CS predicts non-occurrence of US Suppresses behaviour related to US

PAVLOV’S PROCEDURE Trial Type A Trial Type B CS+ CS- US Randomize trial type presentation NEGATIVE CONTINGENCY PROTOCOL CS- US Context cues serve as CS+

Testing for CS- CS- produces absence of CR No CR You’ve produced CS- Haven’t learned anything How to measure nothing… 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

Short Delay Conditioning Strongest and most rapid Simple autonomic responses: 5-30 seconds Quick skeletal responses: 0.5 seconds CS US or

Long Delay Conditioning Other distracting stimuli? Timing estimation required CS US or

Trace Conditioning From “memory trace” Must remember CS Other stimuli interfere trace interval CS US

Simultaneous Conditioning Weaker than short delay CS can’t signal onset of US Not predictive CS US

Backward Conditioning Ignores order; US comes first CS has no predictiveness Might become CS- CS US

Influences in Classical Conditioning

CS-US Contiguity Closeness together in time and/or space Usually, more learning if greater contiguity between CS & US Type of conditioning may influence this e.g., eyeblink vs. taste aversion

CS-US Contingency If-then situation X iff Y Consistency of pairing CS and US Greater contingency, greater learning

Stimulus Features Nature of stimulus affects its conditioning ability Intensity Novelty

Compound Stimuli Two+ simple CSs presented at the same time Paired with US

Overshadowing Salience Exclusive regulation of CR by most salient CS in compound stimuli

Latent Inhibition Repeatedly present neutral stimulus (N) Pair N with US Harder to condition N as CS CS- or habituation

Blocking CS1 -- US CS1 and novel stimulus (CS2) with US CS1 --> CR CS2 --> no or very weak CR

Textbook Error: p. 77 “But suppose we eat two foods, one spicy and the other bland. If we then become sick, thanks to blocking we are likely to develop an aversion to the spicy food -- even though it may have been the bland food that caused our illness.”

Sensory Preconditioing Pair two neutral stimuli repeatedly Pair one with US repeatedly until CR produced Test other stimulus CR produced

Number of CS-US Pairings Acquisition curve Non-linear Asymptote asymptote CR Strength Conditioning Trials

Intertrial Interval ITI Time between each CS-US pairing (i.e., between trials) Generally, around 30 seconds effective

Extinction of CR

Extinction CS without US --> Extinction Weakening and stopping of CR Not forgetting A type of conditioning CS paired with absence of US

Spontaneous Recovery After extinction, let time pass Present CS again (no US) Temporary, small return of CR Shows extinction is not forgetting

Relearning/Reacquisition Effect Extinguish CR Recondition with CS-US pairing Fewer trials required

Putting it Together Strength of CR Trials/Time Spontaneous Recovery Acquisition Extinction Reacquisition Strength of CR CS&US CS alone CS alone CS&US Trials/Time

Theories of Classical Conditioning Associationism, Stimulus Substitution, Preparedness, Rescorla-Wagner

Associationism Linking together of: Contiguity, similarity, contrast Events Memories Actions and consequences Contiguity, similarity, contrast Central to study of learning and behaviour

Ebbinghaus’ Memory Experiments Nonsense syllables E.g., ZOG, PAF, TOB One subject Recite from memory Savings E.g., if 10 trials initially, then after a delay 3 more trials, savings = (10-3)/10 = 7/10 = 70%

Major Findings List length Effects of repetition Effects of time Overlearning Effects of time Role of contiguity Backwards associations Forgetting Curve Time between study and relearning 20min 1hr 8.8hr 1day 2days 6days 31days 100 75 50 25 Percent Savings

Classical Conditioning Innate US-UR reflex pathway CS is associated with the US Through the associative process, CR is produced

Stimulus Substitution Theory Pavlov CR and UR produced by same neural region CS takes on properties of US Substitution CR should be the same as UR

Example: Sign Tracking 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 F = CS F = US

Biological Predispositions Burns & Domjan (2000) Timberlake & Grant (1975)

Problems with SST CS not a complete substitute for US e.g., eyeblink differences Magnitudes CSs produce different responses Omissions and additions Compensatory conditional responses

Preparatory Response Theory Learn responses that prepare organism for US occurrence Sometimes CR same as UR, sometimes different

Example: Drug Tolerance Neurophysiological dependencies Siegel (1975) Contextual stimuli act as CSs Compensatory CR Morphine

Contextual Stimuli Theory Rats on hotplate Between-groups study Independent variables: Morphine or placebo Location of injection (Home or Injection room) Dependent variable: time to lift feet

Results Control (placebo): 13 sec. Exp. Gr. 1 (morphine): 24 sec. (day 1) to 13 sec. (day 4) Injection room gives contextual cues Compensatory CR Exp. Gr. 2 (morphine): Day 1-3 injection room: 24 --> 13 sec. latency Day 4 home room: 28 sec. latency

Interpretation US: Morphine UR: Pain reduction CS: Injection room CR: Pain sensitivity CS prepares rats for morphine injection Body homeostasis

Rescorla-Wagner Theory Contiguity account Associative strength CS acquires limited amount of associative strength on any one trial

Three Factors in Theory Maximum associative strength Difference between current and maximum strength Number of additional CSs

Rescorla-Wagner Equation DVn = c( - Vn-1) DVn: change in associative strength for CS on one trial c: represents salience of CS and US; a constant (0.0-1.0) : maximum associative strength (magnitude of UR) Vn-1: associative strength already accrued by CS

Acquisition Phase Example: set c = 0.25,  = 10.0 Vn-1 starts at 0.0 For the first trial Vn-1 = V1-1 = V0 For the second trial Vn-1 = V2-1 = V1

Total associative strength Vn (or “VTotal”) after two trials: First CS-US pairing: DVn = c( - Vn-1) DV1 = 0.25(10.0 - 0.0) = 2.5 Second CS-US pairing: DV2 = 0.25(10.0 - 2.5) = 1.88 Total associative strength Vn (or “VTotal”) after two trials: V1 + V2 = 2.5 + 1.88 = 4.38 Third CS-US pairing: DV3 = 0.25(10.0 - 4.38) = 1.41

Acquisition Phase  Trial DVn Vn (VTotal) 0 0.00 0.00 1 2.50 2.50 Trials Associative Strength (Vn) 0 0.00 0.00 1 2.50 2.50 2 1.88 4.38 3 1.41 5.79 DV3 4 1.05 6.84 DV2 5 0.79 7.63 6 0.59 8.22 DV1 7 0.45 8.67 8 0.33 9.00 9 0.25 9.25 10 0.19 9.44

Extinction Example: After first extinction trial: Set c = 0.25,  = 0.0 After first extinction trial: DVn = c ( - Vn-1) = 0.25(0.0 - 10.0) = -2.5

Extinction Trials Associative Strength (Vi)  = 0.0 DV1 DV2 DV3

Blocking Learned CS blocks subsequent CSs Example CS = tone, novel CS = light c = 0.25,  = 10.0 Completed 8 trials with just tone, V8 = 9.0 DVn = 0.25(10.0 - 9.0) Only 1 unit of associative strength left to split between the tone and the light Ultimately, Vtone=9.5 and Vlight=0.5