The findings in this group divide into two very different bodies of evidence. The first, from cognitive psychology, is about how individual minds learn, and it is among the most robust research in the social sciences. The second, from the sociology and economics of schooling, is about what institutions can change, and it is far more contested. Both are routinely ignored in practice, for different reasons.
Learning feels wrong when it works
The strongest theme in the cognitive findings is that effective learning feels harder than ineffective learning. The Spacing Effect, first measured by Ebbinghaus in 1885, shows study spread over time outlasting the same study massed together. The Testing Effect shows retrieval strengthening memory more than re-reading. Interleaving produces worse practice and better learning; the Generation Effect favours producing an answer over reading it. Bjork's Desirable Difficulties names the pattern.
The reason people keep choosing the wrong methods is the Illusion of Fluency: ease of processing is mistaken for learning, so re-reading a highlighted chapter feels productive. The Illusion of Explanatory Depth shows people believing they understand everyday mechanisms until asked to explain them. The Worked Example Effect and the Expertise Reversal Effect add that what helps a beginner hinders an expert, so the right method depends on where the learner stands.
Expectations and self-image
A second cluster concerns what teachers and students believe. The Pygmalion and Golem effects find teachers' expectations nudging performance up or down. The Big-Fish-Little-Pond Effect finds able pupils in selective schools thinking less of their own ability than equally able pupils elsewhere. The Dr. Fox Effect found an audience rating a confident lecture highly when it contained no substance, which is a warning about student evaluations.
What institutions can change
The institutional findings are more sobering. The Coleman Report found family background explaining more of the variation in attainment than school resources. The Fade-Out Effect finds early test gains from pre-school programmes largely disappearing within a few years. Class Size Effects were large in a randomised trial and small at statewide scale. The Sheepskin Effect finds earnings jumping in the year a qualification is completed, which suggests that some of what education pays for is the credential. Summer Melt and Undermatching find able low-income students lost between admission and enrolment, or applying below their level.
Where it applies
The cognitive findings apply to anyone who studies or teaches: space practice out, test instead of re-reading, mix problem types, and distrust the feeling of fluency. They cost almost nothing to adopt. The institutional findings apply to policy and are more demanding: they suggest targeting what schools can influence, such as teacher quality and specific transitions, and several have produced cheap interventions, including text-message reminders that reduced summer melt in controlled trials.
Where it is argued over
The cognitive findings are rarely in dispute; the argument is about their limits, since Productive Failure finds some benefit in struggling before instruction, which sits uneasily with the worked-example evidence. The institutional findings are contested on almost every point: whether fade-out means lasting benefits have been lost or merely moved from test scores to later life, whether the Dale–Krueger Finding holds at the top of the income distribution, and whether Summer Learning Loss is real or an artefact of test scaling. Three entries, the Learning Pyramid, the Mozart Effect and the Marshmallow Test, are filed partly as records of how educational claims spread beyond their evidence.
Why it is worth knowing
Few areas of research have such a gap between what is known and what is done. The cognitive evidence could change how almost everyone studies, at no cost, and mostly has not. The institutional evidence is a corrective to the hope that schools alone can equalise outcomes, and also a guide to the specific points where they can make a difference.
The entries behind this essay: Evidence in Learning & Education. Every subject has its essays on the essays page.