Classical Conditioning

1. Classical Conditioning Psychology 485 September 28, 2010

2. Class Outline • Introduction & History • Three major questions: • What is learned? • Why learn through classical conditioning? • How does learning happen?

3. Conditioning in Psychology • Often contrasted to more cognitive approaches • Watson & Little Albert • A premise: Study of simple learning processes will “scale up” to complex cognition

4. Ivan Petrovich Pavlov (1849-1936) • Pavlovian (Classical) conditioning • Physiologist • Digestion • Dogs • Conditional redirection of reflexes  Conditional reflexes

5. The Basics TIME on Conditional Stimulus off on Unconditional Stimulus off (after enough pairings) Conditional Response Unconditional Response

6. What is learned?

7. Past definition of CC • “The originally neutral stimulus, through repeated pairings with the unconditioned one, acquires the response originally given to the unconditioned stimulus” • Intro Psych textbook from 1987 • What is wrong with this definition?

8. Repeated Pairings • Taste aversion • Idea of contiguity • Temporal similarity between presentation of CS and US • i.e. CS and US are presented at the same time • Contiguity is neither sufficient nor necessary

9. Kamin’s blocking effect • During second training, tone & food are contiguous • Contiguity not sufficient

10. Contingency vs Contiguity CS1 CS2 • Which CS would condition more easily? • Contiguity is the same • CS2: US is contingent (dependent) on CS • Contingency, not contiguity

11. Conditioned Inhibition CS1 • No contiguity between CS and US • CS signals absence of US • Conditioned inhibitor • Contiguity is not necessary for conditioning

12. Past definition of CC • “The originally neutral stimulus, through repeated pairings with the unconditioned one, acquires the response originally given to the unconditioned stimulus” • Intro Psych textbook from 1987

13. CR “same as” UR? • CERs (Conditioned Emotional Response) • Pair tone with shock • When rat is shocked, it jumps and increases activity • What tone is presented, rat freezes • Drug tolerance • CSs for drug use cause body to prepare for drug • Body prepares in opposite direction of drug

14. What is learned? • Context • Hierarchical structure • Second-order conditioning • Occasion-setting • Expectancies

15. So what is learned? US Response CS • What type of association is formed? • Stimulus-Stimulus • Stimulus-Response

16. Rescorla (1973) • So, how do you get rid of a response that is hard wired to a stimulus? • How can you get rid of a reflex? • Habituation

17. Results • Less suppression in Habituation group • (In other words, more responding) • Therefore, the connection MUST be S – S

18. So what is learned? Noise Startle Light

19. Why Learn?

20. Ecological perspective • Expectancies • CS helps you predict occurrence of US • Makes animal more able to react to US • Biological relevance • Not all CSs are created equal • e.g. ‘bright-noisy’ water vs novel-tasting water • Hard to condition visual/auditory stimuli to nausea

21. Improving survivability • Blue Gourami • Territory is defended more aggressively when competitor is signaled • Winners become winners • Losers stay losers

22. Improving survivability • Japanese Quail • Signalling opportunity for reproduction • Increases effectiveness of copulation (quicker and more ejaculate) • Increases likelihood of fertilization

23. Improving survivability • Ant Lions • Signal food presentation for larvae • Build better pits • Extract food more effectively • Moult more quickly (quicker to reproduce)

24. Develop Instincts? • Baldwin effect • If there is a reliable predictor of some important event across generations: • Learning faster is better • Learning becomes instinct? • e.g. New predator in environment • Some behaviour makes it difficult for predator to kill prey • Learning behaviour provides survival advantage • Selection: ability to learn improves • Eventually behaviour becomes instinct

25. How does learning happen?

26. Rescorla & Wagner (1972) • Computational model of conditioning • Widely cited and used • Most important paper in animal learning? • Learning as a violation of expectations

27. RW in Pictures Error Calculation

28. RW as Recipe • On every trial: • Look around and examine all your stimuli • Use them to predict what will happen (V∑) • Get a reward/US. How good/big was it? (λ) • How wrong was your prediction? (λ - V∑) • Take a portion of that error (α and β) • Change your prediction for next time (ΔV)

29. RW as Equation • And Voila! You have a learning algorithm. ΔV = αβ(λ - V∑) • λ = the maximum conditioning possible • α = saliency of the CS (between 0 and 1) • β = saliency of the US (between 0 and 1) • VX= associative (predictive) strength of a given stimulus • ΔVX= change in the associative strength of a given stimulus • V∑ = total associative strength of all stimuli

30. RW as equation • Equation describes a change in expectancies • Change in expectancy is based on: • Features of the CS and US • Total possible learning, minus what you’ve already learned • Based on expectation of US

31. Problems with RW model • Does not account for many Classical Conditioning findings: • Spontaneous recovery • Savings • CS pre-exposure (latent inhibition) • Higher-order conditioning • Trial-by-trial based account • Does not account for timing

32. US vs CS Processing • CS processing theories suggest properties of CS affect learning • Attentional theories: it’s adaptive to pay attention to CSs that may signal important events • Also adaptive to not pay attention to CSs that are not likely to signal important events • Pearce-Hall model • Attention to CS changes across trials • α can change from trial to trial