Does learning by teaching work? What research says about the protégé effect

The professor effect is the idea that you learn a topic better when you expect to teach it, or when you really do teach it. You may have felt this before finals or a big exam. You explain a concept to a friend, and halfway through the sentence you realise you never understood it. That moment is uncomfortable, but it shows you exactly where your notes are blurry.

Researchers separate two situations. In the first, you study knowing you will have to teach, but nobody ever shows up. In the second, you teach for real, out loud, to a person or to a camera. Both have been tested, and they do not give quite the same result. There is also a neighbouring idea, the protégé effect, which is about effort more than memory. The next sections take each one in turn and stay close to what each study actually measured.

In two experiments, Nestojko, Bui, Kornell and Bjork (2014) asked participants to study a text. Some expected to teach it afterwards, the others expected to be tested. In reality, nobody taught. Even so, those who prepared to teach produced fuller, better organized recall, and they answered questions better, especially about the main ideas (Nestojko et al., 2014).

So the mere intention to explain changes how people study. You look for the structure, you spot the main points, you ask yourself how you would present each part. For you, that turns into a simple habit. When you reread your biology or history notes, imagine you have to make a classmate who missed everything understand them, and read with that question in mind. The study shows the direction of the effect.

Fiorella and Mayer (2013) compared two ways of doing it. Some people prepared to teach, others actually taught, by explaining the lesson in front of a camera. Actually teaching gave a longer-term benefit than only preparing to teach (Fiorella and Mayer, 2013).

Speaking out loud forces you to finish your sentences. You cannot skip the part you half understand, because the listener, even an imaginary one, will stop on it. That is why a class presentation or an oral exam often reveals gaps that a silent reread let slip by. The authors do not say it works for everyone or for every subject. They describe what happened with their material and their participants, and it is up to you to test what it gives on your own course, at your own pace.

Koh, Lee and Lim (2018) looked for the reason why teaching helps. Their conclusion is nuanced. The benefit comes mostly from retrieval, when you teach without your notes (Koh et al., 2018). When you explain while looking at your sheet, you are reading. When you explain from memory, you go and fetch the information, and that effort is what counts.

This fits what research on testing has shown for a long time, recalling beats rereading, as we detail in Active recall, why quizzing yourself beats rereading. Dunlosky and colleagues (2013) also rank self-explanation among the techniques of moderate utility, and practice testing among those of high utility (Dunlosky et al., 2013). So teaching is a good way to test yourself, as long as you put your notes down before you start. It is not a separate magic method, it is a pleasant frame for doing active recall.

Chase, Chin, Oppezzo and Schwartz (2009) described what they call the protégé effect. Students put in more effort to teach their virtual agent, the one they were teaching, than they did for themselves (Chase et al., 2009). We feel responsible for someone who counts on us, even when that someone is a character on a screen.

This helps explain why it is often easier to get started when you are helping a friend revise than when you sit alone with your notes on a weeknight. Be careful, though. The study is about effort, not about grades or success. Effort is good news, because it leads to more practice. Mostly it makes the session easier to begin, and that already counts for a lot when starting is the hard part.