What is the popularity of using colored (e.g. red) transparencies to obscure words in a language book?

Question

When I was in Japan twenty years ago, I noticed that high school students would sometimes study English from special books with black and red printing inside. The book would come with a red-colored transparent plastic film, a little smaller than the size of a page, which would be used to obscure words that the learner was trying to guess. Words printed in red would be invisible under the transparency.

Here are some photos to give a better idea how it works:

I'm wondering about the popularity of this learning method, since I've never encountered it outside of Japan. Was it ever used in America? Is it still used in Japan? Is there something wrong with the method? Was it just a fad, or was it another instance of Japan being ridiculously advanced education-wise?

Does it even have a name?

Answer 1

This is as AML said, an implementation of the Cloze deletion test but within a book.

Generally, Cloze deletion tests are basically "fill-in-the-blanks" but with the best and grammatically correct word(s). Taking from the link above, we find that:

In addition to use in testing, cloze deletion can be used in learning, particularly language learning, but also learning facts. This may be done manually – for example, by covering sections of a text with paper, or highlighting sections of text with a highlighter, then covering the line with a colored ruler in the complementary color (say, a red ruler for green highlighter) so the highlighted text disappears; this is popular in Japan, for instance.

The correct red text in your book will be hidden by the red card and the student can attempt to fill in with the right word(s). After doing so, the student may remove the card and check their answers.