Key Takeaways
The Productivity Illusion at the Heart of Common Study Habits
Most learners discover highlighting and re-reading in middle school and never seriously question them. They are low-friction, universally modeled, and — critically — they feel like studying. Pages fill with color. Familiar passages become even more familiar. The hours pass with a comfortable sense of progress.
That comfort is the problem. Cognitive science has established that the subjective experience of studying productively and the actual encoding of durable memory are not the same thing, and can come apart dramatically depending on the technique used. Highlighting and re-reading sit at one end of that spectrum: high perceived effort, low actual retention gain.
Understanding why these habits persist — and why they underperform — is the first step toward replacing them. It also helps to know that the habits the research actually supports are not exotic or expensive. They are accessible to anyone willing to tolerate a learning curve that feels a little less smooth.
Myth
Highlighting key passages is an effective way to retain information because it forces you to identify what matters.
Fact
Highlighting improves retention only marginally, if at all, because it does not require the learner to process or reconstruct information.
Selecting text to highlight feels analytical, but the cognitive work involved is minimal. The learner is recognizing importance, not generating understanding. A landmark review published in Psychological Science in the Public Interest rated highlighting and underlining as having low utility for learning, noting that the technique rarely encourages elaborative thinking or connections between ideas. When students return to highlighted passages, they tend to re-read them — compounding the problem rather than solving it.
Myth
Re-reading your notes or textbook chapters multiple times is a reliable way to learn the material.
Fact
Re-reading produces only a small boost in comprehension on immediate tests and very little durable retention over time.
The same major review that flagged highlighting also assessed re-reading and reached a similar conclusion: the technique is widely used but weakly effective. Re-reading raises familiarity, not understanding. Because the text is already organized and readable, the brain does not have to work hard to process it — and effort, it turns out, is closely linked to encoding strength. Retrieving information from memory (as in self-testing) forces reconstruction, which builds far more durable knowledge than passively re-exposing yourself to organized text.
For a deeper look at what the research actually supports, see our article on active recall and why researchers keep returning to it.
Myth
If a study method feels difficult or uncomfortable, it probably isn't working.
Fact
Desirable difficulty — the friction that comes from effortful retrieval — is precisely what drives stronger long-term retention.
Psychologists use the term desirable difficulties to describe learning conditions that slow initial acquisition but substantially improve long-term memory. Self-testing, spacing practice sessions out over time, and interleaving different topics all feel harder than re-reading — and that friction is the mechanism, not a flaw. Learners who interpret difficulty as a sign of ineffectiveness often abandon the most productive techniques in favor of the comfortable, familiar ones that feel like they are working.
Mixing subjects during study sessions is one underused application of this principle — explored in detail in our piece on interleaving and long-term skill development.
Myth
Using multiple colored highlighters helps organize material and makes it easier to remember.
Fact
Color-coding highlights adds visual structure but does not meaningfully increase retention compared to standard highlighting.
Color-coded systems can help with organization, but they do not address the fundamental limitation of highlighting: the absence of retrieval effort. If anything, an elaborate color system can create an additional illusion of mastery — the material looks sorted and studied, reinforcing the mistaken belief that it has been learned. Organization and memorization are distinct cognitive processes, and conflating them leads learners to overestimate how prepared they actually are.
Myth
Re-reading is worthwhile because repeated exposure is how memory works.
Fact
Spaced retrieval — not repeated passive exposure — is the mechanism behind long-term memory consolidation.
The spacing effect, one of the most replicated findings in memory research, shows that distributing practice over time produces far better retention than massing the same amount of practice into a single session. Crucially, spaced practice works best when it involves active retrieval — recalling information — rather than simply looking at it again. Re-reading in a single session exploits neither spacing nor retrieval, making it doubly inefficient. Designing a schedule around these principles is more tractable than it sounds; our guide to building a study schedule you will actually follow walks through the practicalities.
What to Do Instead: Practical Replacements
Replacing passive review habits does not require abandoning your existing materials. Your textbook, lecture slides, and notes remain useful — the goal is to change how you engage with them.
Passive Study Habits Scale Poorly Under Time Pressure
Highlighting and re-reading become especially problematic during exam preparation, when time is limited. Because these techniques provide weak retention gains per hour invested, learners who rely on them often need to review material far more times than peers using active methods. If your schedule is tight, switching techniques is more urgent, not less.
Self-testing is the most direct substitute for re-reading. After reading a section, close the book and write down everything you can recall — without looking. This effortful retrieval is uncomfortable precisely because it is working. Flashcards, practice problems, and end-of-chapter questions all accomplish the same thing.
Elaborative interrogation — asking yourself why a fact is true or how a concept connects to something you already know — is a particularly efficient upgrade from highlighting. Instead of marking a sentence, pause and explain it in your own words before moving on.
Fluency Is Not the Same as Memory
When material feels familiar after re-reading, that sense of recognition is often 'processing fluency' — your brain smoothly parsing text it has seen before. Fluency does not reliably predict whether you can recall or apply that information later. Treating familiarity as a signal of mastery is one of the most common and costly errors in self-regulated learning.
Spaced review sessions replace the habit of re-reading the same material in one sitting. Plan short review sessions 24 hours, 3 days, and one week after first encountering material. Each session should involve retrieval, not re-reading.
These techniques translate directly to online and self-directed learning environments. For a full picture of how to apply them across digital courses, see habits that make online learning stick. And if you want to audit other counterproductive patterns in your current routine, study habits that undermine learning without feeling like mistakes is a useful companion read.
This article is for informational and educational purposes only. Research findings described are based on published cognitive science literature and represent general patterns, not guarantees of individual outcomes.