Even when material has been encoded and stored, two things commonly stop us retrieving it: interference between memories, and the mismatch of context cues between encoding and retrieval.
Interference
Interference is when one memory disrupts another. There are two main types:
Proactive interference (PI) — old material disrupts the recall of new material. Example: you've used the same PIN for years; you change it; you keep typing the old one. Old learning interferes proactively (forwards in time).
Retroactive interference (RI) — new material disrupts the recall of old material. Example: after learning your new PIN you can no longer remember the old one. New learning interferes retroactively (backwards in time).
Interference is strongest when the two sets of material are similar — the same kind of code competing for the same kind of trace. McGeoch & McDonald (1931) demonstrated this: participants learned a list of 10 words to perfection, then learned a second list of either synonyms, antonyms, unrelated words, numbers or did nothing. When asked to recall the original list, those who learned synonyms (most similar) recalled the fewest words, while those who did nothing or learned numbers recalled the most. Similarity drove the interference.
Context-dependent memory
Recall is best when the environmental context matches the one in which encoding took place. Godden & Baddeley (1975) asked deep-sea divers to learn 36 unrelated words either on land or 6 metres underwater, then to recall them in either the same or the opposite environment. Recall was about 40% lower when the contexts mismatched. The external context acts as a retrieval cue.
State-dependent memory
A related effect: recall is best when the internal state (mood, alertness, intoxication) at retrieval matches that at encoding. People learning material when slightly anxious may recall it best when slightly anxious again. The mechanism is the same — internal cues during retrieval.
Why this matters
- Revision strategy: vary contexts (different rooms, different times) so memory isn't tied to one set of cues. Better still, take the practice paper in conditions resembling the real exam.
- Eyewitness testimony: cognitive interview techniques exploit context-dependence by mentally reinstating the scene.
- Distinct from decay: interference shows the trace is still there — it is retrieval that fails when cues are wrong.
⚠Common mistakes— Common errors
- Mixing up proactive and retroactive interference. Mnemonic: Proactive = Past (old) interferes with new; Retroactive = Reaches Round to disrupt old.
- Claiming Godden & Baddeley shows context matters for everything — it is strongest for episodic recall in the absence of strong internal cues; less effect on recognition tasks.
AI-generated · claude-opus-4-7 · v3-deep-psychology