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New learning fades fastest right after it happens, then more slowly. And something that has faded is not gone: learning it again takes less time than learning it the first time. Baccare is built on both ideas. Practice comes back on purpose, a little at a time, before a skill has slipped too far, instead of being covered once and left behind.

In the 1880s the German psychologist Hermann Ebbinghaus memorized lists of nonsense syllables, then measured how long it took to relearn each list after a delay. The time he saved the second time around, called savings, showed how much of the list was still with him. In 2015 two researchers at the University of Amsterdam, Jaap Murre and Joeri Dros, repeated the experiment as closely as they could: one person spent about 70 hours learning lists and relearning them after 20 minutes, 1 hour, 9 hours, 1 day, 2 days, 6 days or 31 days. Their curve came out similar to the original, which is why the forgetting curve is still taught today.

After 20 minutes, relearning took about 58% less time than the first learning in Ebbinghaus's results, and about 47% less in the 2015 replication. After an hour the savings were 44% and 37%. After a day, 34% and 32%. After a month, 21% and 4%. The steepest drop is in the first hour or so, and the decline slows after that. Notice that even a month later, relearning was still faster than starting fresh in both studies: forgotten is not the same as never learned.

The curve is not perfectly smooth. In the original and in the replications, there was less forgetting at one day, two days or both than a smooth curve predicts. The authors point out that research on sleep and memory would predict a boost like this after a night or two of sleep, but they are careful to say that this experiment cannot show sleep is the cause, and that more research is needed.

Nonsense syllables were chosen because they mean nothing, and school learning is the opposite: a fact about the water cycle connects to rain your child has seen, so it usually lasts longer than a list of syllables. The replication also tested a single person. So the curve describes a shape, not a schedule, and not a prediction about any one child. It is not a test of your child's memory, and Baccare does not use it as one. The study is about forgetting, not about the best way to review; the review timing below is our design choice, made with this shape in mind.

Short practice on most days, rather than one long session a week (what ten minutes a day is for). Flashcards from Notes Studio come back on a schedule: a card missed goes back to the start and returns in the same sitting, and each time your child knows a card it waits longer, 1 day, then 2, 4 and 8, until it retires. On Progress, a skill your child mastered but has not practiced in 45 days appears under Needs a refresher, and Plan the week suggests it as Due for review. Right answers your child marked as a guess appear under Guessed last time, so a lucky guess gets a second look. In grades 4 through 8, the Cornell Notes lessons teach children to cover their notes, answer their own questions from memory, and come back to the page over several days.

Ask your child to tell you one thing from today's practice at dinner; saying it from memory is review. When yesterday's skill looks shaky today, that is the curve, not a sign that the practice did not work, and the second time through will go faster. And let the refreshers and review cards do their job: a skill that comes back after a month is not a step backward.