Reviewing in ADHD: Why You Forget What You Learned

You studied a topic. When you finished, you knew it; you could have explained it to someone. Three days later a question on the same topic came up and you have nothing.

For years I read this as my memory being bad. Then I noticed it had nothing to do with memory itself; it had to do with the way I fed information to it.

This article is the review part of the how to study for an exam with ADHD series. In the article on memorization and spaced repetition I described the research side of the spacing effect; here I look at how to turn it into an exam calendar.

Familiarity and remembering are not the same thing

The most common form of review is rereading the notes. You open the page, the lines look familiar, you say "I know this," and you close it.

There is a trap here. Familiarity does not mean the information can be recalled. When you see the text, you recognize it; without the text, you cannot call it up. And in the exam there is no text.

The review by Dunlosky and colleagues, which evaluated ten learning techniques, shows this point clearly. The two most widely used methods, rereading and underlining, stayed in the low-utility category; self-testing and spreading study over time were the two methods given the highest utility (Dunlosky et al., 2013).

So the most common thing you do before an exam may be the thing that helps least.

The power of testing yourself

The classic study by Roediger and Karpicke sets this out very clearly. Participants read passages; one group studied the passage again and again, the other group tested themselves on it.

On the measurement taken five minutes later, the group that kept studying did better. But on the measurement a week later the picture reversed: the group that tested themselves remembered markedly more (Roediger and Karpicke, 2006).

The sneakiest side of this finding is the short-term illusion. While you study, you cannot measure by feel which method is working, because the feeling shows the short term. Reading the notes makes you feel good; testing yourself makes you feel bad, because it shows what you do not know. And the one that works is the one that feels bad.

There is good news on the ADHD side too. In studies with university students, the benefit of retrieval practice came out at a similar size in students with and without ADHD. I wrote about these findings in detail in the article on memorization and spaced repetition.

The interval: when to review

The second thing, as important as testing yourself, is when you test yourself.

Going over the same topic three times in one session and spreading it over three days use the same amount of time but do not give the same result. Review spread over time lasts markedly longer. In the glossary: spaced repetition.

There is a handy rule of thumb for turning this into an exam calendar: set the review interval according to the time left before the exam.

If the exam is three months away: after you learn the topic, review it on day 1, day 7, day 21 and one week before the exam.

If the exam is one month away: day 1, day 4, day 10 and three days before the exam.

If the exam is one week away: the next day, the third day and the last day.

These numbers are not sacred; think of them as ratios. The longer you need to hold the information, the longer the intervals get.

One more detail: a review does not have to be long. The second review of a topic can take fifteen minutes, because you are not learning, you are recalling. Short reviews are especially valuable for ADHD, because putting off a forty-five-minute review block is much easier than putting off a fifteen-minute one.

Studying in a mixed order

The third setting is how you arrange the topics.

Working forty questions of the same type back to back is the most common way of studying. As you solve them you get faster and faster, and that speed makes you think you are learning. Yet most of the time what you are learning is not which method to use; it is that all the questions on that page call for the same method.

The study by Rohrer and Taylor tested this directly. In one experiment students worked on problems of different types either blocked by type or in a mixed order. Test performance was markedly higher in the group that worked in a mixed order (Rohrer and Taylor, 2007).

In terms of exam study, this means: once a topic is done, mix the last questions you solve on it with questions from earlier topics. This is exactly what a practice exam already does, and part of a practice exam's value comes from here. In the article on practice exams and time management I described the other functions of a practice exam.

Closing question. In the last three minutes of every study block, close the book and write three questions on a blank sheet of paper: what did I learn today, which part was hardest, what do I need to review tomorrow. Write the answers too. This sheet becomes the starting point of the next day and removes the question "where do I start" when you sit down at the desk.

In ADHD the real problem is remembering the calendar

What has been described so far is not specific to ADHD; it applies to everyone. The part that is specific to ADHD is this: this whole plan requires remembering to do something three days from now.

The ability to remember to do something in the future is called prospective memory, and it is one of the areas where ADHD struggles most often. On top of that comes the difficulty of feeling time itself: the difference between "three days from now" and "two weeks from now" stays blurry. I wrote about this in the article on what time blindness is.

The only rule that comes out of this is: do not keep the review calendar in your head. Let a system keep it.

A card app that does spaced repetition. It calculates which card comes on which day. Which one you use matters less than always using the same one.

Review appointments put in the calendar. On the day you finish the topic, put three separate reminders in the calendar. With the name of the topic, not just "review."

A review chart on paper. A table hung on the wall: rows are topics, columns are review numbers. You tick the box when you have done it. Being visible is a big advantage over a digital list in ADHD.

Taking notes is part of review too

To be able to review, there has to be something that can be reviewed. Pages and pages of notes taken during a lecture often do not do this job, because when review time comes, rereading those notes takes as long as learning the topic from scratch.

What makes a note reviewable is that it has been turned into question form. Writing "when is this formula used" in the margin of the page is more useful than writing the formula itself, because during review you can close the page and try to answer that question. In the article on taking notes I described this side in detail.

There is also the fact that making cards can itself turn into a way of procrastinating: making the cards pretty, coloring them, sorting them into categories. As a rule, put one question and one short answer on a card, and write the card at that moment while you are studying the topic. Notes that you say "I will turn them all into cards later" most likely never turn into cards.

Four practical forms of active recall

The advice "test yourself" is right but abstract. The concrete version can be one of these four forms.

The blank page method. After studying a topic, close the book and write everything you remember on a blank sheet of paper. The order does not matter, neatness does not matter at all. Then open the book and fill in the gaps in a different color. It takes two or three minutes and is usually the most uncomfortable method, because it immediately shows how little you remember.

Writing your own questions. While reading the topic, write questions in the margin; do not write the answers. The next day, look only at the questions. Because writing questions requires a different mental job from passively reading the text, it also holds your attention during the reading.

Explaining it to someone. Explain the topic to a friend, to a sibling, or out loud to an empty room. The point where you get stuck while explaining is exactly the point you do not know. The glossary counterpart of this method is thinking out loud.

A deck of cards. Cards with one question and one short answer in an app that does spaced repetition. Long paragraphs do not fit on a card and do not get read during review.

What the four have in common is this: trying to recall before seeing the answer. Flipping the card and saying "yes, I knew that" does not count as testing; that is just recognizing. Even trying to remember and failing contributes to learning, because the act of searching strengthens the path to the information.

There is also combining with mixing. When you do the blank page method not with one topic but with three together, retrieval and mixed study happen at the same time. Layering these two methods on top of each other instead of applying them separately is the easiest way to use limited study time more efficiently.

Forgetting is not a defect

Finally, I want to say something about forgetting itself.

Forgetting is not the brain breaking down; it is its normal functioning. Every person loses most of what they learn within days. The difference is that some people make up for this loss without noticing: they hear it once more in class, use it once more in homework, call it up once more while talking with a friend.

In ADHD these automatic make-ups happen less. Attention drifts while listening to the lecture, homework is done on the last night, the topic is seen once and closed. So forgetting is not bigger; the repetition layered on top of it is smaller.

That is why building a review system in ADHD is not an effort to be superior; it is adding from outside the natural repetitions that are missing. And when you do it, you see that your memory was not as bad as you thought.