Ebbinghaus and the study of forgetting
1885, Herman Ebbinghaus embarked on memory research as a solo researcher, using himself as the only participant.
He created lists of random nonsense syllables (consonant–vowel–consonant, e.g., pub, dax, russ, wood) to study memory without meaning.
Rationale:
- If items have meaning, people use semantic cues to remember; Ebbinghaus wanted to strip away meaning to isolate basic memory mechanisms for encoding and retrieval.
Experimental design details:
- Varied list length: 10, 12, 20, 40 items.
- Learning phase: read the list aloud repeatedly until he could recite the entire list in order (his learning criterion).
- Retention tests: after different intervals, he retested himself to see how memory held up.
- Intervals studied: after the initial learning, he varied the delay periods (e.g., 2 days, 3 days, 4 days, 20 days) before testing.
Key concept: the forgetting curve
- On day 1, memory is excellent (perfect recall by his criterion).
- After 24 hours (day 2), about half of the items are forgotten.
- By day 3, memory is very poor, illustrating rapid forgetting for information that is not well encoded.
- This rapid early forgetting characterizes what happens when encoding is shallow or missing.
Relearning and the green lines: the effect of relearning (over multiple sessions)
- Instead of testing on day 2, Ebbinghaus sometimes had himself relearn the list on day 2 until he again reached the memory criterion.
- He then tested memory in subsequent days (day 3, day 4, etc.).
- Result: forgetting is much more gradual when relearning occurs; memory decays more slowly with each subsequent retrieval of the material.
- With repeated relearning to criterion across days, forgetting becomes very small or nearly nonexistent.
- This phenomenon is described as overlearning: continuing to learn beyond initial mastery to create a more durable memory trace.
Practical takeaway: forgetting isn’t inevitable if you engage in relearning/overlearning
- Learning once may suffice for a short-term test, but for durable long-term retention, repeated relearning strengthens memory.
- Ebbinghaus’s findings underpin the value of regular review and spaced repetition in real-world studying.
Savings: how relearning becomes faster over time
- Observation: each time he relearned the list, the time required to relearn decreased.
- Definition: Savings is the reduction in time required to relearn a previously studied item.
- Formal idea (conceptual):
where $T1$ is the time to learn the list the first time and $T2$ is the time to relearn it the second time. - Implication: as you relearn, you not only remember better but also become faster at reacquiring the material.
How this applies to schooling and study habits
- Memory durability improves with periodic review across a course, not just cramming before a test.
- Going back to notes from a previous year, re-reading tests, and revisiting old material can lead to more durable memory traces.
- The phenomenon helps explain why students who space their study over time tend to perform better on exams and retain material longer.
Basic mechanisms: encoding, retrieval, and the role of meaning
- Meaningful encoding typically enhances memory; Ebbinghaus deliberately used meaningless syllables to focus on basic encoding/retention processes.
- Retrieval strengthens memory traces: memory is reinforced every time we retrieve or recall information.
- When information is weakly encoded, forgetting happens rapidly, but retrieval practice and relearning can bolster durability.
Durability of memories and aging: the question of long-term retention
- Even durable memories can fade if not referenced or retrieved over time, but the strength of traces persists with practice and retrieval cues.
Real-world example mentioned in class context
- You may forget some material from a prior course (e.g., Psych 201 if you’re returning next year), but careful review can reactivate and re-stabilize those traces.
- The idea is not personal failure but a natural property of forgetting—and a practical path to resilience: review and relearn.
Transition to longer-term memory questions: Barak and Whitlamer’s decades-long view
- Question: Are memories inevitably fading with age, or can some be retained for decades?
- They investigated long-term memory across decades using yearbooks as naturalistic, stable memory materials.
Long-term memory across decades: Barak and Whitlamer (1975)
Study approach and participant materials
- Participants brought their yearbooks to the study, containing names and faces of classmates learned years earlier.
- Participants ranged from 18 (early in adulthood) to 70+ years old; yearbook ages spanned from a few months to roughly 50 years in the past.
- This design allowed assessment of memory for well-learned social information over decades, with each participant having a similar material but a personal memory set.
Memory tests used
- Free recall: show a face and ask for the name (face-name recall).
- Recognition (face-cued name): show a face with four possible names; pick the correct name.
- Reverse recognition (name-cued face): give a name with four photos; pick the correct photo.
- These three tests examine different retrieval routes: recall, recognition with a cue, and cue-based retrieval via a different modality.
What the x-axis shows
- Time since high school (in years): range from 0.25 years (about 3 months) to 47 years.
- This captures very recent recall to long-term memory spans.
Results by memory type
- Free recall (red line):
- Immediately after high school, recall is about 80% and then shows a dip followed by relative stability through young adulthood.
- Declines gradually into older age, indicating that pure recall of names from a long-ago cohort becomes harder with aging.
- Recognition memory (faces with names or names with faces):
- Generally more stable across age than free recall.
- Picture recognition (recognizing the correct photo given a face) remains particularly robust across the lifespan.
- Name recognition declines later than picture recognition, indicating retrieval is easier when a perceptual cue (a picture) is available.
- Overall pattern:
- Recognition memory, especially picture-based recognition, is relatively resilient to aging compared to free recall.
- Very long-term, overlearned information such as names and faces from high school can be retained for decades with the right cues.
Interpretation and implications
- Highly overlearned, meaningful social material (names/faces from one’s past) can persist across many years, suggesting strong durability for well-encoded, frequently encountered information.
- Access to memories often depends on retrieval cues; a face cue can dramatically aid recall of a name.
- Even after many years, some memory traces persist; aging effects are more pronounced for recall than for recognition, especially cue-rich recognition tasks.
Practical implications for studying and memory strategies
- Importantly, the durability of long-term memories hinges on exposure, encoding richness, and retrieval opportunities.
- In real life, testing yourself with cues (e.g., flashcards with pictures or context) may be more effective than attempting pure recall alone.
- The Barak/Whitlamer work supports the idea that well-supported memories can endure for decades, reinforcing the value of continuous retrieval practice and cue-based retrieval strategies.
Connections to broader memory principles
- Encoding matters: meaningful encoding enhances long-term retention; Ebbinghaus deliberately avoided meaning to study basic mechanisms, highlighting how encoding quality affects forgetting rates.
- Forgetting curve vs. spaced repetition: initial rapid forgetting can be offset by spaced relearning sessions, which reduce the slope of forgetting over time.
- Retrieval practice and the testing effect: memory traces are strengthened with each retrieval, contributing to durability and resistance to forgetting.
- Overlearning and durability: continuing to study beyond criterion strengthens memory, reduces forgetting, and yields savings on future relearning efforts.
- Retrieval cues and access: long-term memory can be robust but may require appropriate cues to access, especially for recall tasks.
Practical study takeaways
Incorporate regular review and spaced repetition to create durable memories, not just last-minute cramming.
Do not fear forgetting: expect some forgetting of poorly encoded material, but use relearning to rebuild and stabilize traces.
Use retrieval-based practices (testing yourself, flashcards, practice recalls) to reinforce memory and reduce the forgetting curve.
Leverage retrieval cues: when studying, pair information with distinctive cues (context, images, associations) to improve long-term accessibility.
For long-term retention of core knowledge, aim for overlearning and varied retrieval contexts to build multiple retrieval routes.
Final reminder from the transcript: memory durability can last for years with proper practice; the key is to relearn, retrieve, and review regularly. Good luck with your own memory!