Luis von Ahn, founder of Duolingo, has given a TED Talk that sounds like a dream come true for many teachers: what if we could make learning as addictive as TikTok or Instagram? He makes his point sharply and relatably: if people don’t return to your lesson or app, you can’t teach them anything. Engagement comes first, effectiveness follows.

And that sounds logical. Anyone who’s ever had a class that completely lost interest after ten minutes knows that motivation is a crucial breaking point. But that’s precisely where the problem lies.

Von Ahn explains how Duolingo taps into the psychological mechanisms that make social media so irresistible: streaks, rewards, rankings, a constant stream of little dopamine hits. It works: millions of people open the app daily. The green owl is the gateway to a new language for many beginners. But this immediately raises an ethical question: do we want learning to become as addictive as social media—while simultaneously recognizing how problematic that addiction can be?

What does the research actually say?

More importantly, even if it were effective in retaining people, what would actually stick? If you type Duolingo into Scholar, you’ll find a wealth of research. I looked at several, but found the quality of the studies varied considerably. I’ll focus on two relatively recent systematic reviews, which provide some context.

The first (Shortt et al., 2023) examined research on Duolingo from 2012 to 2020. What did they find? Most studies focused not on learning outcomes, but on the app’s design and gamification elements. Only a limited number of studies actually examined what students learned. And where they did, it was usually basic vocabulary or repetitive drills. More complex skills, such as communication or listening comprehension, were barely addressed. The authors’ conclusion: we still know far too little about how effective Duolingo truly is for sustainable language acquisition, and the research is often methodologically weak.

The second review (Rouabhia & Kheder, 2024) focused on vocabulary learning. The results are more positive there: students using Duolingo often score better on vocabulary tests and are more motivated than students using traditional methods. The playful interface and gamification elements therefore work, especially when it comes to learning basic vocabulary. However, there are caveats here as well: most studies are small, short-term, and primarily measure whether students can recognise words, not whether they can use them in real-world communication. Moreover, it’s unclear whether the motivation the app generates will be sustained in the long term.

The role of struggle and frustration

Von Ahn himself admits in his talk that frustration is the greatest enemy. Duolingo consciously chooses to make learning as frictionless as possible—preferring slow progress over abandonment. But that’s a trade-off: if you remove all the difficulty, you also take away some of the depth. And anyone who’s ever truly learned something knows that a bit of struggle is often necessary. Research on “desirable difficulties” shows that learning is often more powerful when it doesn’t come naturally (Bjork & Bjork, 2011 and 2020).

I find it a fascinating paradox. Duolingo makes learning accessible, approachable, and fun. That’s an achievement in itself. But when motivation becomes more important than effectiveness, there’s a problem. Engagement should never be the end goal. It’s a means to enable learning, not a replacement for it.

Perhaps that’s the most important message we can take from this talk: let’s make learning attractive, certainly. But let’s also not forget that real progress sometimes comes from those moments when you’re not rewarded, when things are a bit rough, when you persevere because it’s difficult—and not because a cartoon owl is giving you a virtual high five.

Chocolate on broccoli

Gamification can, in this sense, act like a layer of chocolate on the broccoli of learning: it makes the first bite more appealing, but it doesn’t change the broccoli itself. If we’re not careful, the candy taste lingers and we forget what it was all about: perseverance, practice, and embracing even the less enjoyable aspects of learning.