How Memory Works

HOW MEMORY WORKS the desk between the firehose and the archive — sensory → working → long-term 1 · SENSORY MEMORY eyes · ears skin · nose ATTN everything hits, < 1 second iconic ~0.5s (sight) echoic ~2s (sound) ~99% evaporates ATTENTION is the filter: only what you attend to gets to the desk. a few get through 2 · WORKING MEMORY — the desk 4 8 15 a face phone # this idea 5th → displacement: new shoves old off rehearsal loop keeps it alive ~15-30s tiny: ~4 chunks (Miller 7±2, refined) · volatile this is where THINKING happens a CHUNK = one meaningful unit: F-B-I = 1 chunk, not 3 letters ENCODING (write) deep/meaning > rote RETRIEVAL (read) needs a CUE · recall strengthens it → 02 3 · LONG-TERM MEMORY — the archive ARCHIVE ≈ unlimited · can last a lifetime NOT a recording — a RECONSTRUCTION (rebuilt each recall, and editable) EXPLICIT (you can state it) SEMANTIC facts: 'Paris=capital' EPISODIC events: 'my 18th' IMPLICIT (you just do it) PROCEDURAL skills: cycling, typing CONSOLIDATION: sleep files desk → archive (hippocampus → cortex) THE FORGETTING CURVE — Ebbinghaus, 1885 100% 0% time → forget fast then level off each review re-lifts it AND flattens the next drop → spaced repetition 02 SAME SHAPE AS A COMPUTER'S MEMORY HIERARCHY (→ How Computers Work) MIND COMPUTER why it matches Sensory buffer NIC / DMA buffer fleeting, overwritten instantly Working memory registers + RAM tiny, fast, VOLATILE (lost on restart) Long-term memory disk / SSD big, slower, PERSISTENT Encode → consolidate write → fsync not durable until flushed Forgetting lost pointer / bit-rot data may exist, but no cue to find it shop on K8s: working memory ≈ a pod's RAM (evicted on restart) · long-term ≈ the Postgres volume (survives). A crash before the write is fsync'd = you 'forgot' it. Sleep is your brain's fsync. JARGON, DECODED encoding — getting info in (the write) storage — holding it over time retrieval — pulling it back out (the read) chunk — one meaningful unit cue — a trigger that unlocks a memory consolidation — stabilising it (mostly in sleep) rehearsal — looping it to keep it on the desk displacement — new items shove old off the desk iconic / echoic — visual / auditory sensory trace semantic / episodic — facts / lived events procedural — skills you do without words reconstruction — memory is rebuilt, not replayed ONE LEVEL DEEPER — SLEEP: WHEN THE WRITE-BACK HAPPENS the rest of this track says 'sleep = your brain's fsync'. This is the actual mechanism behind that line. the problem sleep solves: a fast cache vs a slow store HIPPOCAMPUS fast, writes today's episodes, SMALL — fills up, will overwrite ← by day: write here → NEOCORTEX vast, slow to learn, permanent, where schemas & skills live if you never moved data from cache to disk, the cache would overwrite it. Sleep is the transfer — 'systems consolidation'. one night = ~5 cycles; the two stages do different jobs awake deep NREM (early night) REM (late night, near waking) 0h ~8h NREM slow-wave sleep (deep, early night) • hippocampus REPLAYS the day's traces — the same neurons fire, sped up ~20× • it teaches the neocortex, slowly, offline • strengthens & MOVES facts to permanent store REM sleep (dreaming, late night) • integrates new memories into existing SCHEMAS — links, gist, creative recombination • emotional tone gets processed/dampened • why a problem 'looks clearer in the morning' the evidence (Rasch & Born 2013): targeted memory reactivation — replay a SOUND or SMELL from learning during NREM → better recall. what this means for the vault: • your last review before sleep gets consolidated overnight — timing your hardest cards there pays off • an all-nighter doesn't just tire you — it CANCELS the consolidation window; the encoding never becomes permanent • this is exactly why spaced repetition works WITH sleep between reps → "Spaced Repetition". Sleep is the write-back; spacing schedules the next read.