On this page
Two students study the same solved example from their physics book. One reads it, nods and moves on. The other stops at every line and asks, "Why this step? Where did that come from?" Decades of research suggest the second student learns more from the same page. This habit is called self-explanation, and it is one of the easiest techniques to start using today.
What did Chi's research on self-explanation find?
Michelene Chi and colleagues published a landmark 1989 study in Cognitive Science. They recorded students thinking aloud while studying worked examples of mechanics problems. The "Good" students generated many explanations: they worked out the conditions under which each step applied and connected the steps to principles in the text. They also monitored their own understanding accurately. The "Poor" students generated few explanations, misjudged what they understood, and later leaned heavily on the examples when solving new problems.
A 1994 follow-up asked whether self-explaining could be prompted. Fourteen eighth-grade students were asked to explain to themselves after reading each line of a passage on the human circulatory system. Ten students in a control group read the same text twice. The prompted group gained more from pretest to posttest, and every "high explainer" ended up with the correct mental model of the circulatory system.
How strong is the evidence?
A 2018 meta-analysis in Educational Psychology Review by Kiran Bisra and colleagues pooled studies in which learners were prompted to self-explain. The British Psychological Society's summary reports 64 studies with nearly 6,000 participants and an average effect size of g = 0.55. Two details matter for how you use it: there was some limited evidence that multiple-choice style prompts were the least effective, and explanations about your own state of knowledge ("I get this") helped less than explanations of the material itself.
For balance: in their 2013 review of study techniques, John Dunlosky and colleagues rated self-explanation "moderate utility", partly because it had not been adequately evaluated in real classrooms at the time.
How do I self-explain a worked example?
At each line of a solution, cover the next line and answer these prompts out loud or in the margin.
What principle is being used here? Name it: Newton's second law, energy conservation, Kirchhoff's rule.
Why this step, and not another? What made the author choose it?
What conditions make it valid? No friction? Constant acceleration? Inertial frame?
How does it connect to the previous line? What was substituted or rearranged?
What would change if the problem changed? Double the mass, flip the direction, remove friction.
Then predict the next line before you uncover it.
Worked example: a block sliding down a rough incline
A block of mass m slides down an incline of angle θ with coefficient of kinetic friction μ. Find its acceleration.
Line 1: Forces are mg, the normal force N, and friction f = μN up the slope. Self-explanation: "Kinetic friction opposes the block's motion relative to the surface, and the block moves down the slope, so friction points up it."
Line 2: N = mg cos θ. Self-explanation: "There is no acceleration perpendicular to the incline, so the forces in that direction balance. The perpendicular component of gravity is mg cos θ."
Line 3: ma = mg sin θ − μmg cos θ. Self-explanation: "Newton's second law along the slope. Gravity's component down the slope is mg sin θ; friction subtracts."
Line 4: a = g(sin θ − μ cos θ). Self-explanation and check: "Mass cancels. If μ = 0, a = g sin θ, the frictionless result. If μ cos θ is larger than sin θ, a comes out negative, which means a block already sliding would slow down."
That last check is the habit Chi's "Good" students showed: working out the conditions under which a result holds and testing it against cases you already understand. Our piece on John Sweller's cognitive load theory and the worked example effect explains why studying solved problems this way suits beginners.
Using a step-by-step solver the self-explanation way
Step-by-step solutions are most useful when you engage with each step rather than read the whole thing at once. The Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning; before reading each step, say what you expect it to be and why, then compare. If you cannot name the principle behind a step, look it up in the Fermi Concept Library, which gives every concept in physics, chemistry, biology, mathematics and computing its own lesson.
For explaining with others, see how to run a study group that actually helps.
Take one solved example from today's chapter and write a self-explanation beside every line.
