Current Theoretical Approaches and Issues in Classical Conditioning

1. Current Theoretical Approaches and Issues in Classical Conditioning Psychology 3306

2. Everything you know is wrong • So, the number of pairings is an important, maybe all important, variable in determining the amount of conditioning, right? • Fine, then explain Kamin Blocking to me…

3. Kamin (1968) L = Light T = Tone + = CS (shock)

4. Blocking is rocking • Same number of tone shock pairings in both groups • It is NOT just number of pairings • The tone predicts nothing in the blocking group (nothing extra anyway) • These results, and some others, lead to the Rescorla Wagner Model

5. You said there’d be no math! • Yes, it is a math model • Trial by trial • Assumes you can get excitatory conditioning, inhibitory conditioning or nothing • All based on what the CS predicts • Let’s look at the rules

6. The Rules • If the strength of the US is greater than expected then excitatory conditioning to the CS is the result • If the strength of the US is LESS than expected, then you will get inhibitory conditioning • The larger the discrepancy between what is observed and what is expected, the greater the conditioning

7. More rules • The more salient the CS, the more conditioning you will get • Two or more CSs together, their strength is additive • This is, in essence, a model of surprise! The more surprised the animal, the more it learns

8. The model makes some groovy predictions • Slope of the acquisition curve • Blocking • Conditioned inhibition • Overshadowing • Overexpectation

9. Overexpectation

10. The Model: • ΔVi – Si(Aj-Vsum) • i = CS • j = US • S = Salience • A = Value of the US • V = amount of conditioning • These quantities are, of course, hypothetical

11. An example • OK, say a food pellet = 100 • Say salience of a light CS = .2 • Vsum = 0 (at the start of the experiment, there is no conditioning yet

12. OK, now for the numbers • Trial 1 • ΔVi – Si(Aj-Vsum) • =.2(100 – 0) • =20 • Trial 2 • ΔVi = .2(100-20) • =16

13. Continued…. • Trial 3 • ΔVi – Si(Aj-Vsum) • ΔVi = .2(100-36) • -12.8 • And so on…. • Less and less conditioning as time goes by • Coo eh

14. Overshadowing • CS1 -> Light, S = .2 • CS2 -> Noise, S= .5 • 2 CSs, so two calculations per trial • Trial 1 • ΔVLight = .2(100-0) = 20 • ΔVNoise = .5(100-0) = 50

15. Overshadowing • Trial • ΔVLight = .2(100-70) = 6 • ΔVNoise = .5(100-70) = 15 • OK, how does blocking work? • Well there is no strength left • Conditioned inhibition? • Negative for old CS • Additive model

16. Stuff it cannot deal with • CS preexposure • Change S? • Mackintosh’s attentional theory does this, S becomes an attention parameter • Pearce Hall model • Gallistel’s model

17. Types of associations • First order conditioning is S-S • Second order is S-S and S-R • CS - context associations too • US context associations • Context Blocking • CS CS associations in compound stimulus experiments • Occasion setting (Holland)

18. Constraints on Pavlovian Conditioning • Taste aversions • Not just sickness • Not the aftertaste • Only to certain elements of the food, which depends on the species • Special? • Could just be a quantitative difference (Andrews and Braverman, 1975)

19. Form of the CR • CR is often like the UR but not always • Weaker • Opposite direction • Drug tolerance • Compensatory CRs with opiates • Context as CS • Shooting gallery effect • Could depend on drug action being in PNS or CNS (Stewart et al)

20. Physiological Basis • New synapses formed in Aplysia • Increase in transmitter release in neurons sensitive to CS (very cool) • Just like habituation! • What about more complex creatures

21. Five points about Physiology and conditioning • 1) CR and UR pathways are often different • 2) CR production is distributed • 3) Conditioning is distributed • 4) Different CRs, different brain regions • 5) Sometimes it is individual neurons • My conclusion then is that we have a very basic mechanism at work here