This "research" has no controls, no blinding, no quantitative data. The historic work mentioned all come from a time when there was no reliable way to confirm that someone was actually asleep. The recent research is full of weasel words like suggests, seems like, appears to, with no actual hard facts to measure and review.

So called Sleep Learning systems have been around for over 100 years but to date there is no rigorous suggesting that any of them work for acquisition of new information and/or skills.

I'll never understand HN's fascination with obvious pseudo science.