Spaced practice
Cepeda, Pashler, Vul, Wixted & Rohrer (2006), Psychological BulletinWhat it measured
A meta-analysis of hundreds of experiments on when to review: memory is more durable when reviews are spread out than when they are crammed, and the best gap grows with how far away the test is.
What it doesn't say
Most studies used lists of words or facts and tests within days or weeks. The benefit for complex skills is real but less precisely mapped.
In BrainyGym
Each review is scheduled right before you would forget it, from how you answered last time, not on a fixed calendar.
Retrieval practice
Roediger & Karpicke (2006), Psychological ScienceWhat it measured
Students who took a test after one reading remembered more a week later than students who reread the text, even though rereading felt more effective to them.
What it doesn't say
University students and prose passages; a single week. The effect is one of the most replicated in the field, but the size varies with the material.
In BrainyGym
Every module asks you to answer before it lets you reread: quiz first, cards second, then explaining it in your own words.
Interleaving
Rohrer & Taylor (2007), Instructional ScienceWhat it measured
Mixing problem types during practice lowered scores during the session but raised them on the test a week later, compared with practising one type at a time.
What it doesn't say
Maths problems with students; the benefit shows when the types are easy to confuse. For unrelated topics it is smaller or absent.
In BrainyGym
The daily session alternates concepts from the same course that are easy to mix up, so you learn to tell which one applies.
The 2013 synthesis
Dunlosky, Rawson, Marsh, Nathan & Willingham (2013), Psychological Science in the Public InterestWhat it measured
A review of ten study techniques across hundreds of experiments: practice testing and spaced practice rated high utility; rereading and highlighting rated low; self-explanation moderate.
What it doesn't say
A review, not a new experiment. "Moderate" for self-explanation means promising with less evidence, not proven.
In BrainyGym
The Feynman step, explaining a concept in your own words to Brainy, rests on that moderate rating. We say so rather than oversell it.