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You can't learn anything useful from scratch while asleep, and subliminal persuasion is dead. Re-cueing memories learned awake (targeted memory reactivation, TMR) works a little in the lab, about g = 0.13–0.29 depending on how one corrects for publication bias. The one technique that looked strong, closed-loop auditory stimulation, has regressed to roughly zero for memory. Nobody has tested whether personalization rescues any of it.
| Claim | Best evidence | Verdict |
|---|---|---|
| Learn new material in sleep | Koroma 2022: N=22, 59% vs 50% chance, implicit only; Züst 2019 word pairs in slow-wave up-states | Real but tiny and unconscious. Awake learning hit 88% after 4 exposures vs 59% after ~40 in sleep |
| TMR boosts awake-learned memories | Hu et al. 2020: 91 experiments, 2,004 people, g = 0.29; skills ~0.44–0.51, language 0.40, declarative 0.23, REM ~0 | Small, bias-adjusted 0.13–0.18, I² = 71%. Effects fade by 6–8 weeks (Carbone & Diekelmann 2024) |
| TMR changes attitudes or habits | Implicit-bias result failed replication (Humiston & Wamsley 2019, power 0.9) | Don't count on it |
| Closed-loop slow-wave stimulation | Harlow et al. 2023: 12 studies, effect falls from d ≈ +0.99 (2013) to −0.39 (2021); publication year explains 92% of heterogeneity | Boosts slow waves, not memory (Henin 2019) |
| Consumer sleep headbands for memory | Elemind's evidence is sleep onset (IEEE Spectrum); no peer-reviewed memory RCT found for any device | Don't buy one for learning |
| Home TMR | Göldi & Rasch 2019: N=66, null overall; helped undisturbed sleepers, hurt those the cues woke | Possible only if the cues never wake the sleeper |
| Subliminal self-help audio | Greenwald 1991 double-blind, 237 people: content did nothing, perceived gains followed the label | Placebo |
| Subliminal priming generally | Independent replications average d ≈ 0.002 vs 0.40 when an original author is involved (Meta-Psychology) | Mostly not real |
Two things sit outside memory. Targeted dream incubation (Dormio) reported creativity scores 43% higher than an unincubated nap in N=49, per MIT News, with no standardized statistics. Two-way communication with lucid dreamers works but rarely: 29 correct answers from 158 attempts (Konkoly 2021).
The gap is real: I found no study where personalized cue timing, cue selection or a per-person model improved a memory outcome. Phase-targeting algorithms work technically, and one 2025 preprint (N=28) predicted memory responders with AUC 0.92, post hoc and with trends only at p ≈ 0.07.
The harder problem is the target. Harlow et al. found the memory-benefit score has test-retest reliability of about r = .01, so per-person optimization would be fitting noise. And because slow waves can be pushed up without memory following, a closed-loop optimizer would happily optimize the wrong variable. A personalization project here would need many nights per person and a within-person cued-vs-uncued design before it could learn anything.
The defensible practice is boring: study before sleep and spread material across nights. For tinkerers, low-volume odor or sound cues on half of tonight's items, with the other half as control, is cheap. Expect a small effect at best.
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