This is a highlighter. It costs barely a few dollars, and there is probably one sitting in your pencil case right now.
In two thousand thirteen, five psychologists reviewed decades of research on ten study techniques and gave a utility rating to each one. Highlighting received the lowest rating. Rereading and making summaries scored at the bottom as well. Exactly the techniques that almost every student uses.
But the highlighter is not even the worst tool on my list. There is a technique that makes your notebook look gorgeous, feels even more productive, and ranks below it. And out of the ten techniques, only two earned the highest possible score. Almost nobody uses one of them as their primary study method. I will tell you which one shortly.
This is an episode about why the study habit that feels most productive teaches you the least. I am going to rank the most famous techniques on a tier list, from top to bottom. And there is one technique that does not fit into any tier.
1. Every study technique passes one single test: does it make you think?
To rank any technique, you need to understand what happens inside your brain when you study. In twenty seconds: your working memory is the workbench where active thinking takes place. It is tiny, holding only about four items at a time. Your long-term memory is the filing cabinet where everything you need on test day is stored. And only the material you actively processed on your workbench ever reaches that filing cabinet.
So the question to rank any technique is simple: does it force you to think? And be careful, because thinking is not the same as staying busy. Copying an entire whiteboard keeps your hand busy and puts your brain on vacation.
Be careful because there is a trap. Easy techniques feel like they work. You reread the chapter, everything looks familiar, and you conclude that you learned it. That is the illusion of fluency. Recognizing information when it sits right in front of you is completely different from recalling it when the exam paper is blank.
Keep this question in mind: does this make me think? Let us see if you understood. In which tier would you place the technique of “highlighting the textbook”?
2. Highlighting: the favorite technique of students.
Everyone has owned a textbook that was more yellow than white by the end of the semester. If everything is highlighted, nothing is highlighted. You made zero choices, you simply painted. Highlighting feels great because you feel like you are separating the key points. But in reality your hand does the physical work while your brain just watches.
If you cannot let go of your highlighter, at least highlight with clear criteria. Use one color for concepts, another color for examples, and another color for formulas. That way you force yourself to decide what each passage represents. And deciding means thinking.
But the way most people highlight? Tier D.
3. Pomodoro: everyone recommends it. But is it really a study technique?
In truth, Pomodoro is not even a learning technique. It is a focus technique. Twenty-five minutes of concentration followed by a five-minute break. It exists to keep you sitting at your desk studying instead of jumping to your phone every three minutes.
It does not force you to think. But it protects your mental workbench where thinking happens against a flood of notifications. That already solves half the problem. Tier B.
4. Spaced repetition: study less each day to remember more.
Spaced repetition means studying the same subject across several different days instead of doing everything at once. Instead of cramming for five hours the night before the exam, you study one hour a day across five days.
Why does this work? Because between one study session and the next, you forget a little bit. And having to search your filing cabinet for something that has already started to fade is the exact cognitive effort that locks in memory. Your brain realizes: “This comes back repeatedly, so it is worth keeping.”
Does this sound more demanding than bingeing everything at once? It does. And that is exactly why it works. Tier S.
Do you remember the two techniques that earned top marks in the two thousand thirteen review? This is one of them. The other one has not even appeared yet. And when it shows up, it will upend the entire ranking.
5. Rewriting clean notes: the neatest notebook in the room.
You take your messy class notebook, three colored pens, a ruler, and a highlighter, and you rewrite everything with neat handwriting. Two hours later the notebook looks gorgeous and you feel like you had a productive day.
What actually happened on your mental workbench? Almost nothing. You transcribed words. The information entered through your eyes and left through your hand without ever passing through your filing cabinet. And if your workbench is busy choosing the marker color for the title, it is not busy understanding the material.
Reviewing notes like this is not studying. It is calligraphy. Tier F. Rewriting clean notes only copies. But what if, instead of copying, you had to explain the idea? With no book, no notes, to someone who knows nothing about the subject?
6. The Feynman technique: it seems easy until you try it.
The Feynman technique means explaining the material as if you were teaching a twelve-year-old child. You start with confidence, and halfway through the explanation, you freeze: “Wait… why does this happen again?”
The part you thought you knew was only familiarity. Explaining the idea out loud exposes the missing gap immediately. It passes the test with ease. Tier A.
7. Mind maps: beautiful, organized, and almost always done wrong.
Mind maps are useful. You look at the material from above and you see how topics depend on each other and how concepts connect. But notice one detail: most people draw their mind map with the textbook wide open, copying headings directly into bubbles. Once again, that is just transcription in a prettier layout.
To actually benefit from a mind map, you have to draw it from memory. Close the textbook. Sketch what you remember, and only then open the book to fill in the missing pieces.
It helps, but it does not do the heavy lifting. Tier B.
Up to this point, only one technique reached tier S. And the technique that does not fit into any tier has not even appeared yet. I will get to it shortly. Before that: if you want a method that combines focus, review, and paper practice, I invite you to visit this link.
8. Summaries: they can be great or useless. It depends on your method.
One type of summary simply copies the textbook using fewer words. That is just rewriting clean notes under another name, and you already saw where that ended up. And there is the summary where you read, close the book, and write in your own words. That takes real effort, because you have to choose, rephrase, and connect.
The problem is that most people do the first type: six pages of summary with the book open right beside them.
Do you want to raise your summary to a higher tier? Hide your summary. Take a blank sheet of paper, write down what you remember, and then check what was missing. There: your summary just became retrieval material from your filing cabinet. Keep that idea in mind, because it will come right back.
The way most students do it, summaries sit in the middle of the ranking. Tier C.
9. Active recall: the most uncomfortable technique on this list.
Active recall means closing your study material and trying to remember. A blank sheet of paper, flashcards, or past exam questions, it does not matter. What matters is pulling the information out of your mental filing cabinet without looking at the answer.
It feels uncomfortable: you make mistakes and your mind goes blank. And that exact friction is what builds long-term memory.
Tier A. For now. I will return to it soon.
10. Rereading: the twin sister of highlighting.
Rereading is the illusion of fluency in its purest form. On the second reading everything looks familiar, and your brain confuses “I have seen this before” with “I actually know this”.
Run this experiment: take the chapter you reread yesterday, close the book, and try to explain the three main points out loud. If you freeze, you did not learn the material. You merely recognized it.
It belongs right beside highlighting. Tier D.
11. Elaborative interrogation: the kid question that makes you learn.
Elaborative interrogation means asking “why?” about every concept. Quick test: why is an air conditioner installed high up on the wall? Think for a second. Because cold air is denser and sinks. Done: you just connected a household appliance to a high school physics lesson. And it never ends. Next you can ask yourself why cold air is denser?
Every “why” anchors the new information to something that already lives in your filing cabinet. And well-anchored information is much easier to retrieve later, because you have multiple pathways to reach it.
It forces you to truly think. Tier A.
12. Interleaving: you will make more mistakes. And you will learn more.
Interleaving means mixing different types of practice problems instead of solving them in identical blocks. That creates discomfort: you make more errors, you slow down, and you feel like you are struggling. It feels worse, and during the study session it genuinely is more difficult.
When you practice in predictable blocks, the question you need to solve is obvious in advance. You never train for the hardest part of the exam, which is looking at a blank question and figuring out which mental tool to apply. On a real exam, problems are never organized by chapter.
Tier S.
Notice the overall pattern: the higher the tier, the more uncomfortable the technique feels. The psychologist Robert Bjork, from the University of California, Los Angeles, gave a name to this: desirable difficulties. It is the difficulty that gets in the way right now and locks in memory later.
13. The technique that does not fit into any tier.
So tier S belongs to spaced repetition and interleaving. Do you remember the question I asked you to keep in mind? If active recall is so powerful, why is it not here? Because now I need to reveal something I kept hidden until this point.
Spaced repetition tells you when you study. Interleaving tells you in what order you study. But neither of them tells you what you actually do during your study session.
If you space out rereading, you are simply rereading with time gaps. If you interleave highlighting, you are merely highlighting in a different order. Spacing and interleaving multiply the effect of something. And zero multiplied by any number is still zero.
And what do they need to work? They need active recall, searching the filing cabinet without looking. Active recall without spacing still produces results. Spacing without active recall barely works at all.
That is why active recall moves out of tier A and rises directly into the GOD tier. If I had to choose a single study technique from this entire list, this would be the one.
In practice, here is how it works. Finished studying? Close everything. Blank sheet of paper. Write down what you remember. Then check what was missing. Repeat after one day, after three days, and after seven days. And when you practice problems, mix up the topics. Spaced and interleaved active recall: that is the combo.
Most people study with habits that create a feeling of learning without real comprehension. Rewriting notes, highlighting, and rereading leave knowledge sitting passively on your mental workbench. The top techniques force you to visit your filing cabinet and pull out what you know, and that active retrieval effort is what builds lasting memory. The complete tier list ended up like this. Tier GOD: active recall. Tier S: spaced repetition and interleaving. Tier A: the Feynman technique and elaborative interrogation. Tier B: Pomodoro and mind mapping. Tier C: summaries. Tier D: highlighting and rereading. Tier F: rewriting clean notes.
Notice the paradox: the study habit that feels easiest and most productive teaches you the least, while the habit that exposes your mistakes is what helps you pass your exams.
To build your spaced review plan on paper and retain what you study, I invite you to visit right now this link.