Homer orders a subliminal cassette tape to help him lose weight, but is accidentally sent one that helps him increase his vocabulary after the weight-loss tapes sell out. [...] Homer puts on the headphones in bed and falls asleep. When he wakes up, he is suddenly articulate.
I found some articles (in Spanish) and other references (including an article in the Oxford Journal) about how such method improves memory recall just by listening to audio material during the REM (Rapid-Eye Movement) phase of sleep.
I'm wondering if such learning methods are effective.