Highlighting is one of the first things many readers do when a book feels important. A coloured line seems to preserve a sentence, declare a judgement, and create a path back through the chapter. Yet does highlighting actually help a reader understand and remember, or does it mainly make the page look as though learning has taken place?
The honest answer is conditional. Highlighting can support later review when it is sparse, accurate, and followed by active work. It is weak as a complete study method because selecting words from a page does not necessarily require the reader to explain their meaning. The distinction matters for anyone who wants a book to remain usable after the first reading, rather than merely recognisable when opened again.
What the evidence says
John Dunlosky and colleagues assessed common learning techniques in a 2013 review for Psychological Science in the Public Interest. They rated techniques according to the evidence available, the range of conditions in which they worked, and their practical value. Practice testing and distributed practice received high-utility ratings. Highlighting and rereading received low-utility ratings as general methods.
A low rating does not mean that every mark is harmful or that no reader should ever use a highlighter. It means the method, by itself, has limited support across learners, materials, and tasks. Highlighting is especially vulnerable to poor calibration. Readers often mark too much, mark familiar lines, or select sentences because they sound polished rather than because they carry the argument.
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Why highlighting feels so productive
Marks provide visible evidence of activity. They divide a long chapter into apparent units and make a later session feel manageable. When the eye returns to a marked sentence, the material is easier to process because it is familiar and visually signposted. That ease can be mistaken for knowledge, a form of fluency illusion.
Rereading intensifies the same effect. The second encounter is smoother, and the reader can anticipate the next claim. If a test asks for recognition, this familiarity may be enough. If the reader must produce an explanation without the text, the advantage can disappear. The page has become easier to navigate, but memory has not necessarily become more independent.
How to make highlighting less passive
Use a highlighter as a routing device, not as a substitute for thought. Before marking, identify the question you are trying to answer. A line earns attention when it states a central claim, changes the direction of an argument, defines a term, supplies important evidence, or qualifies an earlier point. If half the page is marked, the marks no longer perform much selection.
Delay some marking. A reader who waits until the end of a section has more context for judging what matters. Another useful limit is to mark only one or two sentences per page, although the right quantity depends on the density of the prose. In the margin, add a short label such as “definition,” “evidence,” or “objection.” Labels turn isolated lines into an outline.
What to do instead, or after
The strongest replacement for passive review is retrieval. After a section, close the book and answer a few questions from memory: What was the claim? How did the author support it? What would count against it? Where could the idea be applied? Only then return to the highlights to check accuracy. The act of answering is the main event; the marked text is a correction aid.
Distributed practice adds time between those attempts. A short summary written after the chapter can be tested again days later. The difficulty of recovering an idea after a delay is useful when the aim is later recall. Rereading can then serve a narrower purpose: repair a missing step, examine a quotation closely, or compare the author's wording with your own account.
Writing about reading is another strong complement. Graham and Hebert's 2010 review found that tasks involving writing about texts can support reading comprehension. The benefit comes from composing, not from accumulating transcription. A paragraph that explains an argument in your own language will usually tell you more about your understanding than a page covered in colour.
The utility ratings below summarise Dunlosky and colleagues' categories, with plain-language explanations. They are ratings of general usefulness, not a ranking of every possible classroom or reading situation.
| Technique | Utility rating | Plain-English note |
|---|---|---|
| Practice testing | High | Try to retrieve the material before checking the answer. |
| Distributed practice | High | Return to the material across separate sessions. |
| Self-explanation | Moderate | Explain why a claim follows and how it connects to what you know. |
| Elaborative interrogation | Moderate | Ask why a fact or claim is true, then supply an explanation. |
| Rereading | Low | Useful for clarification, but weak when it is the only review. |
| Highlighting | Low | Can locate important text, but marking alone demands little retrieval. |
A practical reading sequence
Read a section with a purpose, mark sparingly, and pause before the next section to reconstruct the point. Write a short account that includes the claim, the support, and your response. On a later day, use the account as a prompt rather than opening the chapter immediately. If you cannot explain a point, consult the marked passage, revise the account, and test it again later.
This sequence preserves what highlighting does well, namely navigation and selection, while adding activities that make the reader retrieve and organise meaning. It also keeps the method proportionate. Not every book deserves a detailed apparatus, and not every sentence needs to be converted into a permanent note.
Common questions
Does highlighting help you remember what you read?
Highlighting alone has low general utility in the review by Dunlosky and colleagues. It can help when used sparingly to select passages that are later explained, questioned, and retrieved without the book open.
How much of a book should I highlight?
There is no universal percentage, but highlighting should leave clear differences between central material and supporting detail. If nearly every paragraph is marked, use shorter margin labels or write a section summary instead.
Is rereading better than highlighting?
Both are mainly forms of restudy, and neither is as dependable as retrieval practice or spaced review. Rereading is valuable for resolving confusion, while highlighting is valuable for locating selected passages.
What should I do after highlighting a chapter?
Close the book and write what the chapter argued, how it supported the argument, and what you think follows from it. Then check the highlights for omissions and inaccuracies.
What is the best alternative to highlighting?
Use a combination of brief retrieval, spaced review, and explanation in your own words. A question beside a passage is often more useful than a colour because it creates a prompt for later thinking.