The Von Restorff Effect: Why Highlighting Everything Means Remembering Nothing

Read this list once: table, chair, sofa, chipmunk, dresser, bookshelf, stool.

Close your eyes. What do you remember?

The chipmunk. Obviously the chipmunk. You didn't try to remember it. Your brain just grabbed it, because it was the one thing that didn't belong.

That automatic grab has a name: the Von Restorff effect. And once you understand how it works, you'll also understand why the most popular study habit on the planet, highlighting, quietly fails most students. Your highlighter isn't the problem. The way you use it is.

What Is the Von Restorff Effect?

The Von Restorff effect (also called the isolation effect) is the finding that when you see a group of similar items, the one that stands out gets remembered best. Different color, different size, different category, different anything. Distinctiveness earns memory.

The effect is named after Hedwig von Restorff, a German researcher who published the original study back in 1933. She showed people lists where most items were similar and one was different, and found that memory for the odd one out was consistently better. Nearly a century of research since has confirmed it across colors, fonts, sizes, meanings, and formats.

Your brain does this because it's a difference detector. It can't treat every piece of incoming information as equally important, so it uses contrast as a shortcut for "this one matters." The weird item gets deeper processing. The uniform items blur together.

You've felt this. You remember the one lecture where your professor showed up in a Halloween costume. You remember the single red slide in a deck of white ones. You remember the chipmunk.

Why Does Highlighting Backfire?

Here's where it gets uncomfortable. Highlighting works, when it works at all, through the Von Restorff effect. A yellow sentence on a white page stands out, so your brain treats it as important and remembers it a little better.

Which means the entire benefit depends on contrast. And contrast is exactly what most students destroy.

Think about the last textbook page you highlighted. How much of it was yellow? If you're like most students, the answer is somewhere between "a lot" and "all of it." When 80% of the page glows, nothing is isolated anymore. You've turned the distinctive signal back into uniform noise. The effect doesn't weaken. It disappears.

A large 2013 review of study techniques by John Dunlosky and colleagues rated highlighting as one of the least effective methods students use, partly for this reason. Later research added nuance: selective highlighting can still help, especially when you re-read a passage soon after marking it. The keyword is selective. A highlighter used on 5% of the page is a memory tool. Used on half the page, it's a coloring activity.

The Catch Nobody Tells You About

There's a second problem, and it's sneakier than over-highlighting.

The Von Restorff effect is a trade-off, not a free bonus. Studies going back to the 1970s found that when students read passages where someone else had already highlighted key sentences, they remembered the highlighted material better but the non-highlighted material worse, compared to students reading a clean copy.

Distinctiveness borrows attention. It doesn't create it. When you make one fact stand out, the surrounding facts pay for it.

That's fine when the standout fact is genuinely the most important thing on the page. It's a disaster when you highlighted the wrong sentence, or when the exam asks about the paragraph you left plain. So the skill isn't "make things stand out." It's choosing the right things, and accepting that everything else steps back.

One more finding worth knowing, because it shows how deep this runs. Researchers tested whether the effect only works when the odd item surprises you after a pattern forms. It doesn't. Even when the distinctive item comes first in a list, before your brain has seen any pattern to break, it still gets remembered better. Distinctiveness isn't just a cheap attention trick. It changes how the memory gets encoded.

How to Use the Von Restorff Effect While Studying

The principle behind every tactic here is the same: isolate little, isolate deliberately.

Set a highlighting budget. One or two sentences per page, maximum. If everything feels important, you haven't figured out what's important yet, and that's the actual studying you need to do. The decision is the work.

Make the weird version of the fact. Boring information doesn't have to stay boring. Turn the formula you keep forgetting into something absurd: a mnemonic, a ridiculous drawing in the margin, a sentence that rhymes. This is why memory palaces lean on bizarre imagery. Weird is sticky.

Change the format of what matters most. Write the three make-or-break concepts of a chapter on a single index card in huge letters, or say them out loud while everything else stays silent reading. The production effect works partly through the same distinctiveness mechanism: spoken words stand out from the sea of words you only read.

Put one hard thing in the middle of easy things. Since your brain naturally blurs the middle of any study session (the serial position effect strikes again), placing one oddball item there fights the sag. A surprise flashcard from a different subject dropped into your deck wakes attention right where it dips.

Test instead of tint. Here's the honest truth about highlighting: even used perfectly, it's passive. A stronger way to make a fact distinctive is to get it wrong on a quiz. Miss a question and the correction stands out in your memory the way no yellow marker can. If you'd rather not write your own questions, StudyLab can generate a quiz from your PDF in seconds, and every question you miss becomes a chipmunk in the furniture list.

Common Mistakes to Avoid

Highlighting on the first read. You can't know what's distinctive before you know what's normal. Read first, mark on the second pass.

Making everything colorful. Five highlighter colors with a complex code feels organized. To your memory, it's uniform noise with extra steps.

Forgetting the trade-off. Whatever you isolate steals attention from its neighbors. Choose standouts because they matter, not because they were easy to spot.

Confusing "memorable" with "understood". The Von Restorff effect gets a fact into memory. It doesn't build understanding around it. Pair it with techniques that force explanation, like desirable difficulties that make you work for the meaning.

FAQ

What is the Von Restorff effect in simple terms?

When several similar things appear together, the one that's different gets remembered best. A red word in a black list, an animal in a furniture list, a spoken sentence among silent ones. Your brain prioritizes whatever breaks the pattern.

Does highlighting actually help you study?

Only a little, and only when it's selective. Research rates highlighting among the weakest study techniques, mostly because students mark too much, which erases the contrast that made marking useful. One or two sentences per page, marked on a second read, is the version that can help.

Is the Von Restorff effect the same as the isolation effect?

Yes, they're two names for the same finding. Some papers also call it the distinctiveness effect. All three describe better memory for items that differ from their surroundings.

Can I use the Von Restorff effect for exam prep?

Yes, in two ways. Make your most important facts genuinely distinctive: weird imagery, a format change, one bold card among plain ones. And remember the trade-off, so you only isolate the facts worth the cost. For coverage of everything else, active testing beats visual emphasis every time.

Why do I remember random things but forget what I study?

Because random things are distinctive and study material usually isn't. A weird meme breaks the pattern of your day, while page 47 of your notes looks exactly like page 46. The fix is making the material that matters look, sound, or feel different from the pages around it.

Make It the Chipmunk

Pick the one concept this week that keeps slipping away from you. Now make it impossible to blend in: draw it ridiculous, say it out loud, put it alone on a card in letters too big to ignore.

Then let a quiz do the isolating for you. Upload your notes to StudyLab, take the generated quiz, and watch how the questions you miss become the facts you can't forget.