Explore the evidence
17 of 88 decisions · clear everything
Testing yourself beats rereading — robust in real classrooms; honest durable size ~0.1–0.3 SD, biggest after delay, thinnest on transfer.
strong supportconf: highgc: lowRetrieval practice (the testing effect) · practice · ages 8–18 · method
Spacing beats massing at equal total time — the most robust finding in learning science. Space repetitions at ~10–20% of how long you need to remember.
strong supportconf: highgc: lowSpaced (distributed) practice · practice · ages 6–18 · method
Physical capacity is about as heritable as cognitive ability (~60%, no shared environment). Whether trainability is a stable trait remains unproven — the skeptics are winning.
strong supportconf: highgc: lowTalent and trainability — what is heritable, and what that does not license · talent · ages 4–18 · input
High-dosage tutoring is education's most reliable lever: ~0.29 SD in trials, ~0.2 well-scaled — not Bloom's 2σ. Groups of 3–4 work; 1:1 is unnecessary.
strong supportconf: highgc: lowTutoring — the honest effect, the Bloom 2-sigma myth, and what survives scale · tutoring · ages 5–18 · method
The 10,000-hour rule is dead: practice explains ~14% of performance variance, is itself heritable, and identical twins 20,000 hours apart didn't differ. Necessary, insufficient.
mixedconf: highgc: mediumDeliberate practice and the 10,000-hour rule · deliberate-practice · ages 6–18 · method
Feedback on the task helps modestly; feedback on the person backfires — a stable third of studies reverse. The famous 0.4–0.7 number has no computed source.
mixedconf: highgc: lowFeedback and formative assessment · feedback · ages 5–18 · method
Mastery learning moves tests of what it taught (~0.25) and barely moves independent measures (~0.05) — and time-to-mastery gaps widen, converting ability differences into time.
mixedconf: highgc: lowMastery learning (teach → test → reteach to criterion → advance) · mastery · ages 6–18 · method
Most measured 'home environment' effects are parents' genes: three-quarters of parent-child transmission isn't rearing, and a whole better childhood buys ~4 IQ points.
mixedconf: highgc: lowThe early home environment — what parents can and cannot causally move · early-childhood · ages 4–10 · input
Later bells buy adolescents 40+ measured minutes of sleep — the best-identified positive effect in the archive; the achievement payoff is real but far smaller.
strong supportconf: mediumgc: lowDo later school start times increase adolescent sleep, and does that raise achievement? · health · ages 11–18 · input
Unassisted discovery loses to explicit teaching; well-scaffolded guided discovery beats both. The operative variable is guidance, not ideology.
moderate supportconf: mediumgc: lowExplicit instruction vs discovery/inquiry — how much guidance? · instruction-style · ages 4–18 · method
Mixing problem types helps where confusion is the enemy — discriminating similar categories, mixed math practice — and is useless or worse for facts and prose.
moderate supportconf: mediumgc: lowInterleaving (mixing problem types vs blocking) · practice · ages 10–18 · method
Outdoor time prevents myopia from starting (not progressing); screening plus free glasses raises test scores in children who need them. Two claims, both real.
moderate supportconf: mediumgc: lowVision — outdoor time against myopia, and screening and correction for achievement · health · ages 4–18 · input
Novices learn faster studying solutions than solving problems — then the effect reverses with expertise. Use worked examples early; fade them.
moderate supportconf: mediumgc: lowWorked examples (studying solutions vs solving problems) · instruction-style · ages 10–18 · method
Correcting a real deficiency moves cognition (iron in anaemic children: 0.79 SD); supplementing already-fed children moves nothing (35 RCTs, 19,343 children).
mixedconf: mediumgc: lowBreakfast, school meals, and micronutrients — what feeding children actually buys · health · ages 4–18 · input
A missed day costs little (~0.005 SD); interventions reliably buy days back cheaply, but nobody has shown the recovered days move achievement.
mixedconf: mediumgc: mediumChronic absenteeism — does raising attendance raise achievement? · time · ages 4–18 · input
What parents are asked to DO is the whole effect: tutoring a skill d≈1.15, listening to reading 0.51, reading aloud ~0.18 — same parent, same child. All deflate under better designs.
mixedconf: mediumgc: mediumThe parent as instructor — what survives when the person teaching is the person who raised the child · homeschool · ages 4–18 · method
School exercise programs don't raise achievement: four of the five largest RCTs are null, and more dose doesn't rescue it. Exercise for health, not for grades.
no effectconf: mediumgc: lowPhysical activity as an input — dose, fitness, and school outcomes · health · ages 4–18 · input
The URL is the state — any view you build here is a permalink you can hand to someone mid-argument.