Agree, I shouldn't have used the word "proved". But there is a lot of robust evidence for it going back to the 1800s. Many of the studies are linked to on the w

Agree, I shouldn't have used the word "proved". But there is a lot of robust evidence for it going back to the 1800s. Many of the studies are linked to on the wikipedia page https://en.wikipedia.org/wiki/Spacing_effect https://en.wikipedia.org/wiki/Spacing_effect