The Science Behind Spaced Repetition

The most effective study technique ever discovered started with a 19th-century German psychologist memorizing nonsense syllables.

Ebbinghaus and the Forgetting Curve

In 1885, Hermann Ebbinghaus ran an experiment on himself. He memorized lists of meaningless syllables ("WID," "ZOF," "KAF") and measured how long he retained them. The result: a sharp decay curve. Within 20 minutes, he'd forgotten 42% of what he learned. Within 24 hours, 67%.

But he also discovered something crucial: each re-study session made the forgetting curve shallower. The second time he learned the list, retention lasted longer. The third time, even longer.

This is the foundation of spaced repetition.

Why Spacing Works

Your brain doesn't treat all memories equally. Memories you access frequently get tagged as "important" and consolidated into long-term storage. Memories you never access get pruned.

Spaced repetition exploits this system. By recalling information just before you'd forget it, you signal to your brain: "this matters — keep it." Each successful retrieval strengthens the memory and extends the interval until the next review.

Cramming does the opposite. You dump information into short-term memory, pass a test, then let it decay completely. Three months later, nothing remains.

The Algorithm

Modern spaced repetition systems (Anki, SuperMemo, EA Coach) use algorithms to schedule reviews:

• Correct recall → interval increases (1 day → 3 days → 10 days → 30 days → 90 days)
• Failed recall → interval resets to short (re-learn it)
• Easy recall → interval accelerates faster (you clearly know this)

After a few months of daily 20-minute sessions, a well-designed SRS can maintain thousands of facts with minimal effort.

Why This Matters for Tax

The EA exam covers an enormous surface area: thresholds, rates, filing status rules, penalty tiers, form numbers, exceptions to exceptions. You can't cram this. You need the knowledge to stick through Parts 1, 2, and 3 — which could span a year.

Spaced repetition is the difference between "I studied this last month but forgot" and "I still know this cold."