PSY402 Theories of Learning Monday March 10, 2003

Contemporary Theories Shift from global theories (e.g., Hull’s drive theory) to theories about specific aspects of learning. Global theories were about operant responding not classical conditioning. An animal’s biology influences whether, what, and how fast it can learn. Cognitive view requires emphasis on specific cognitive processes.

Contemporary Theories (Cont.) Classical Conditioning: Nature of the CR – stimulus substitution theory and SOP theory Predictiveness of the CS – Rescorla-Wagner associative model, comparator theory, attentional theory, retrospective processing approach. Operant Conditioning: Nature of reinforcement Behavioral economics

Stimulus-Substitution Theory What is the nature of the CR – is it just the UCR or is it different? Pavlov – stimulus-substititon theory: The CS stimulates the same areas of the brain as the UCS, producing the same response. Activation of CS with UCS establishes neural connection between brain areas.

Conditioned Opponent Response The CR and UCR are often different: CR of fear is different than UCR of pain. Siegel – best evidence of difference: Morphine (UCS) produced analgesia, reduced pain (UCR) Light or tone (CS) produced hyperalgesia, increased pain (CR). Rats remove paws from heat quickly with CS, slowly with UCS. Insulin (glycemia) works the same way

Drug Tolerance Overdoses Elimination of a CS results in a stronger response to the UCS, drug. Extinction of responding to environ-mental cues strengthens drug response Changing the context in which a drug is administered increases response to the drug. Novel environment does not elicit an opponent CR.

SOP Theory Sometimes Opponent-Process theory (SOP) – explains why CR varies. UCS elicits primary A1 (fast) and secondary A2 (longer) responses. A1 & A2 can be same or different. Conditioning only occurs to A2 – the CR is always an A2 response. When A1 & A2 differ, UCR & CR differ.

Two-Phase Reactions Shock – results in: Morphine – results in: A1 -- Initial agitated hyperactivity A2 -- Long-lasting hypoactivity (freezing) CER elicited by CS is A2 Morphine – results in: A1 – sedation or hypoactivity A2 – hyperactivity two hours later CR elicited by CS is hyperactivity

More Support for SOP Theory Rabbit eyeblink mechanisms support the idea of two-phases. Backward conditioning – learning occurs if the CS is presented just before the peak of the A2 response. Larew – conditioning occurred with a 31 sec lapse but not 60 sec or 1 sec.

Affective Extension of SOP Theory Why do different A2 responses have different optimal CS-UCS intervals? Two distinct UCR sequences activate distinct A1 & A2 sequences: Sensory Emotive These distinct sequences can have different strengths, time scales (latencies), or eliciting CS’s.

Rescorla-Wagner Theory There is a maximum associative strength between CS and UCS. UCS determines the limit Strength gained on each training trial depends on prior training. More learning early, less later on Rate of conditioning varies. Conditioning of a CS depends on prior conditioning to other stimuli.

UCS Preexposure Effect If the UCS is encountered without the CS prior to pairing of the two, less learning occurs. UCS becomes associated with other environmental stimuli (without CS). Since there is a limit to association strength, some is drained off by such prior associations. CS-UCS association is weakened.

Problems with Rescorla-Wagner Overshadowing – salient cues have more associative strength. Sometimes a salient cue potentiates another cue instead of overshadowing. Garcia says cues are indexed. R-W says cues are seen as unitary stimulus. Unclear which explanation is correct.

More Problems CS preexposure effect – appearance of CS without UCS prior to learning weakens learning. Shouldn’t have any effect according to Rescorla-Wagner theory, but it does. Cue-deflation effect – extinction of a more salient cue enhances learning for the less salient cue. Should be no change according to R-W.

Comparator Theory If two CS’s are associated, extinction of one should reduce responding to the other. Sometimes true, other times not. CS-UCS associations exist for many stimuli but are exhibited only for the strongest. CS’s are judged in relation to each other.

Attentional View Mackintosh – learned irrelevance occurs during preexposure of CS. Animals exposed to a novel stimulus exhibit an orienting response. No orienting with preexposure. Habituation results in failure of conditioning. Pairing of CS/UCS in novel context results in learning.

Retrospective Processing Most theories assume the level of responding will be constant after learning. Baker & Mercier suggest association can change after learning. Retrospective processing – CS-UCS contingency reevaluated after learning. Backward blocking – support for theory Suggests animals have mental representations, memory for events.