Study Techniques: Ranked by Evidence (What Works, What Doesn't)

In 2013, cognitive psychologists John Dunlosky and colleagues published a landmark review in Psychological Science in the Public Interest evaluating the scientific evidence for 10 of the most common study techniques. The results were striking: the most popular techniques are among the least effective, and the most effective techniques are among the least commonly used. Here is the full picture.

High Utility Techniques

Practice Testing (Active Recall): The single most evidence-supported study strategy. Instead of re-reading or reviewing notes, you actively retrieve information from memory — using flashcards, practice exams, or covering your notes and attempting to recall the content. The "testing effect" — discovered over a century ago and replicated hundreds of times — shows that retrieval practice produces dramatically better long-term retention than repeated study exposure, typically by a factor of 2–4x. Spaced repetition software (Anki) systematizes this by scheduling cards for review at optimal intervals for long-term retention.

Distributed Practice (Spaced Practice): Spreading study sessions across time rather than massing them into a single session produces significantly better long-term retention — the "spacing effect," one of the most robust findings in learning science. Study for 1 hour today, 1 hour next week, and 1 hour the week after: total 3 hours, much better retention than 3 hours the night before the test. The difficulty of returning to material after an interval — it feels harder — is actually the mechanism that produces the retention benefit (desirable difficulty).

Moderate Utility Techniques

Elaborative Interrogation: Asking "why?" and "how?" while studying. "Why is this true?" "How does this connect to what I already know?" This elaborative processing creates more connections in long-term memory and produces better transfer (applying knowledge to new contexts). More effective than re-reading but requires active engagement that makes it harder to sustain.

Self-Explanation: Explaining the material to yourself (or others) as if teaching it. Identifying steps in a worked example, explaining why each step is taken. This forces identification of gaps in understanding and activates elaborative processing. Less evidence-rich than testing and spacing, but consistently positive across studies.

Interleaved Practice: Mixing different types of problems within a study session rather than blocking by type. Counterintuitive — blocking feels more effective because you get better faster within the block, but interleaving produces better long-term retention and transfer because it forces the learner to identify which strategy applies to which problem.

Low Utility Techniques

Re-reading: The most common study strategy. Among the least effective. Re-reading produces a familiarity illusion — the material feels known because it's familiar, not because it can be recalled. Dunlosky's review rates it as low utility. One careful reading followed by retrieval practice outperforms multiple re-readings.

Highlighting and Underlining: Nearly as popular as re-reading, nearly as ineffective. Highlighting is passive — it requires minimal cognitive engagement and produces minimal encoding benefit. The research consistently shows no meaningful retention advantage for highlighted material over unhighlighted material. Exception: highlighting specific items to retrieve later through testing is useful, but the benefit is the testing, not the highlighting.

Summarizing: Writing summaries of material shows inconsistent benefits in the research — helpful for learners trained specifically in summarization, unhelpful for untrained summarizers. The trained vs untrained distinction matters: if you know how to extract key concepts and express them concisely, summarizing works; if you're summarizing verbatim, it's re-writing, not learning.

Keyword Mnemonics: Associating unfamiliar words with familiar ones through imagery. Works well for vocabulary learning but does not transfer to complex, meaningful material. Limited utility scope.

Imagery for Text: Creating mental images while reading. Mixed and generally weak evidence for meaningful material. Better evidence for concrete content than abstract.

The Optimal Study Protocol

Based purely on the evidence: study a topic once carefully (with self-explanation), then test yourself repeatedly with spaced intervals, using interleaved practice once multiple topics are being studied. This is the study approach of the top 5% of students, and it requires about the same total time as re-reading — while producing dramatically better outcomes.

Conclusion

The gap between popular study strategies and evidence-based ones is large. Most students use re-reading and highlighting — the least effective strategies — and wonder why they don't retain what they study. The alternative is available, free, and well-documented: test yourself, space your practice, interleave topics, and explain the material to yourself. The investment in learning these methods pays off every subsequent study session for the rest of your life.