In 2013 a team led by John Dunlosky reviewed the evidence for ten common study techniques and rated highlighting and underlining as "low utility". That finding is often quoted as "highlighting does not work", which is not quite what the review said. It said that highlighting, as most students do it, adds little to plain reading, and that in some conditions it can hurt. It also pointed at what helps. This article lays out both, because the conclusion for a reader is not "stop highlighting" but "highlight differently and then do something with it".
What the research actually found
- Highlighting alone barely beats reading. Across studies going back to the 1970s, students who highlighted while reading recalled about as much as students who simply read. The act of marking is not the act of learning.
- Too much highlighting can hurt. When students marked a large share of the text, they did worse on tests requiring inference than students who read without marking. Heavy marking flattens the text; nothing stands out, and attention to connections drops.
- Marked material is remembered at the expense of unmarked material. Highlighting focuses later attention on the marked lines, so if the highlights are poorly chosen, the wrong things are learned. This is the "isolation effect": marked items become more memorable partly because everything else becomes less so.
- Careful selection helps. In studies where students were trained to highlight selectively, or where the marking was done by someone who knew the material, later recall of the marked points improved. The benefit comes from the quality of the selection, not the presence of colour.
- Highlights help when they are used again. Reviewing highlighted material, especially by trying to recall it before rereading, produces the gains that highlighting on its own does not.
Why marking feels productive and is not
Highlighting produces a feeling of engagement. Your hand moves, the page changes, the passage looks important. But memory researchers distinguish between processing that is fluent (easy, feels like learning) and processing that is effortful (harder, actually builds memory). Highlighting is fluent. It does not require you to understand the passage, restate it, connect it to anything or retrieve it later. Those are the effortful acts that the strongest techniques, practice testing and spaced review, are built from. A highlight is at best a bookmark for effortful work to be done later, and most highlights are never visited again.
The conditions under which highlighting helps
| Condition | Why it matters | How to do it |
|---|---|---|
| Selective: a small fraction of the text | Forces a judgement about what matters; keeps the isolation effect working for you | Read the section first, then mark at most one line per paragraph |
| Meaningful: marks carry a purpose | Later review knows what each mark is for | Use a small colour code (claim, evidence, term) |
| Followed by retrieval | Recall, not rereading, builds durable memory | Cover the marks and try to recall them; check; repeat days later |
| Turned into your own words | Restating exposes gaps and links ideas | Write a one-line note per yellow mark |
| Spaced | Memory strengthens most when review is spread out | Review highlights after a day, a week, a month |
A routine that makes highlights work
- Read a section to the end without marking.
- Go back and mark selectively using a simple colour code: the point in yellow, the proof in green, terms in pink.
- Close the book or tab and write, from memory, one sentence per yellow mark. Then open it and correct yourself.
- The next day, read only your sentences and try to recall the evidence for each. Check against the green marks.
- Turn pink marks into flashcards or a two-column list and test yourself on them at increasing intervals.
- Before an exam or a piece of writing, work from your notes, not the highlights. The highlights were scaffolding.
Steps 3 to 5 are practice testing and distributed practice, the two techniques Dunlosky's review rated as high utility. Highlighting's real job is to make those steps quick to set up. Our guide on turning highlights into notes gives a worked example.
Does any of this change on a screen?
Not the psychology. Digital highlighting is as passive as the paper kind and easier to overdo because it is effortless to undo. Two things do change. Digital highlights can be exported and collected, which makes the retrieval routine easier to run across many sources. And digital highlights can be shared as links, which turns a private mark into a pointer for someone else; that is a communication act, not a study act, and it is what the highlight link tool on this site is for. Use the right kind for the job.
For teachers
Students highlight because nobody has shown them anything better and because it feels like work. Teaching the routine above, especially the read-first-then-mark habit and the write-from-memory step, is one of the highest-return study skills lessons available, and it takes one class period. See highlighting for teachers for activities.
The practical follow-ups to this evidence are elsewhere in our pages on studying with highlights: a three-colour code for textbooks and PDFs puts selective marking into practice, and turning marks into study notes covers the retrieval step that makes highlights worth making.
Common questions
Is highlighting an effective study method?
On its own, no: research rates it low utility. It becomes useful when highlights are selective, carry meaning, and are followed by recall practice spaced over days.
Why do students highlight if it does not work?
It feels productive, it is easy, and it produces a visible result. Fluent activities feel like learning even when they build little memory.
Is underlining better than highlighting?
The research treats them together; neither is better. What matters is selectivity and what you do afterwards.
How much of a page should I highlight?
Very little. A working ceiling is one line per paragraph, often none. Heavy highlighting has been linked to worse performance on questions requiring inference.
What study techniques work better than highlighting?
Practice testing (recalling from memory) and distributed practice (spacing review over time) have the strongest evidence. Highlighting works best as a way to set them up.
Does highlighting help with reading comprehension?
Selective highlighting after reading a section can support comprehension by forcing a judgement about the main point. Highlighting during a first read tends not to.
Sources
- Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J. and Willingham, D. T. (2013). Improving Students' Learning With Effective Learning Techniques. Psychological Science in the Public Interest, 14(1), 4-58.
- Roediger, H. L. and Karpicke, J. D. (2006). Test-enhanced learning. Psychological Science, 17(3).
- Fowler, R. L. and Barker, A. S. (1974). Effectiveness of highlighting for retention of text material. Journal of Applied Psychology, 59(3).
- Peterson, S. E. (1992). The cognitive functions of underlining as a study technique. Reading Research and Instruction, 31(2).