Learning and Memory
Learning is a relatively permanent change in behavior due to experience; memory is the encoding, storage and retrieval of that information. The AAMC outline tests the two associative learning paradigms — classical and operant conditioning — plus observational learning, the multi-store model of memory, and mechanisms of forgetting. Expect several discrete questions on reinforcement schedules and memory stages.
Classical Conditioning
Discovered by Ivan Pavlov, classical conditioning pairs a neutral stimulus with a reflex-eliciting stimulus until the neutral stimulus alone elicits the response.
- Unconditioned stimulus (UCS)
- Naturally triggers a response (food).
- Unconditioned response (UCR)
- The natural reflex (salivation to food).
- Conditioned stimulus (CS)
- Formerly neutral stimulus that, after pairing, triggers a response (bell).
- Conditioned response (CR)
- The learned response to the CS (salivation to bell).
Related processes: acquisition (learning the association), extinction (CR fades when CS is presented without UCS), spontaneous recovery (CR returns after rest), generalization (similar stimuli trigger CR) and discrimination (distinguishing the CS from other stimuli).
Operant Conditioning
B.F. Skinner showed that behavior is shaped by its consequences (Thorndike’s law of effect). Reinforcement increases behavior; punishment decreases it. "Positive" means adding a stimulus, "negative" means removing one.
| Add stimulus (positive) | Remove stimulus (negative) | |
|---|---|---|
| Increase behavior (reinforcement) | Give a treat | Turn off an annoying alarm |
| Decrease behavior (punishment) | Add a scolding | Take away a phone |
- Fixed-ratio — reward after a set number of responses (piecework pay). High steady rate.
- Variable-ratio — reward after an unpredictable number of responses (slot machines). Highest, most resistant to extinction.
- Fixed-interval — reward for the first response after a set time (weekly paycheck). Scalloped pattern.
- Variable-interval — reward after unpredictable time intervals (checking email). Slow, steady.
Variable schedules produce the most persistent behavior. Shaping reinforces successive approximations toward a target behavior.
Observational and Other Learning
Albert Bandura’s Bobo doll experiment demonstrated observational learning (modeling) — learning by watching others, mediated by attention, retention, reproduction and motivation. Related concepts include latent learning (Tolman: learning without reinforcement, revealed later), insight learning (Köhler), and biological constraints such as instinctive drift and taste aversion (Garcia effect).
Memory Systems
The Atkinson–Shiffrin multi-store model describes three stages:
- Sensory memory
- Brief (<1 s iconic, ~4 s echoic), high capacity.
- Short-term / working memory
- ~7 ± 2 items (Miller’s magic number), ~15–30 s; Baddeley’s working memory adds the central executive, phonological loop and visuospatial sketchpad.
- Long-term memory
- Effectively unlimited; split into explicit/declarative (episodic + semantic) and implicit/nondeclarative (procedural, conditioning).
Encoding is aided by elaborative rehearsal, chunking, the self-reference effect, and mnemonics (method of loci). Retrieval is boosted by cues, context and state dependence, and the spacing effect. The serial position effect yields better recall for first (primacy → LTM) and last (recency → STM) items.
Worked MCQs
Five MCQs covering the high-yield testing patterns for learning and memory.
Q1. In Pavlov’s experiment, after conditioning, the bell that triggers salivation is the:
The bell was neutral, then became a conditioned stimulus (CS) after pairing with food (UCS). Salivation to the bell is the conditioned response (CR); salivation to food is the UCR.
Q2. A slot machine that pays out after an unpredictable number of plays uses which schedule of reinforcement?
Reward after an unpredictable number of responses is a variable-ratio schedule, which produces the highest, most extinction-resistant response rate — the basis of gambling behavior.
Q3. Taking away a teenager’s phone to reduce rule-breaking is an example of:
Removing a desired stimulus (the phone) to decrease a behavior is negative punishment. Negative reinforcement would remove something aversive to increase a behavior.
Q4. Recalling the first and last items on a list better than the middle demonstrates the:
The serial position effect combines primacy (early items rehearsed into long-term memory) and recency (last items still in short-term memory). Middle items suffer from both.
Q5. A patient with hippocampal damage can no longer form new long-term memories but remembers events before the injury. This is:
Anterograde amnesia is the inability to form new memories after an injury, classically linked to hippocampal damage (patient H.M.). Retrograde amnesia is loss of memories formed before the injury.
Quick Recap
- Classical conditioning (Pavlov): UCS→UCR, CS→CR; acquisition, extinction, spontaneous recovery.
- Operant conditioning (Skinner): reinforcement increases, punishment decreases behavior.
- Positive = add stimulus; negative = remove stimulus.
- Schedules: variable-ratio is most resistant to extinction.
- Bandura: observational learning via modeling (Bobo doll).
- Memory: sensory → short-term (7±2) → long-term (explicit vs implicit).
- Serial position effect = primacy + recency.
- Anterograde (no new memories) vs retrograde (loss of old) amnesia.