I came across an interesting article today on an artificial intelligence system that helps powers Duolingo.

If you’re unaware, Duolingo is the most popular learning and educational app in the world with ten of millions of subscribers who do a combined 1 billion(!) exercises each day. Duolingo offers roughly 100 language-learning courses and its users complete lessons on reading, writing, listening, speaking, and more. Duolingo is a prominent example of gamification in learning as users earn points to win prizes and reach higher levels. Personally, I’ve enjoyed using Duolingo over the years to improve my Spanish and Italian and often laugh out loud as I read its hilarious short stories (my favorite Duolingo activity).

In any event, behind Duolingo’s simple and cheerful interface are advanced artificial-intelligence systems. One of the difficulties of building a successful learning app is creating challenging and engaging lessons while all the while not overburdening and discouraging users. And that’s where “Birdbrain” comes in.

As its creators explain, Birdbrain is an AI system that estimates the difficulty of a particular exercise and the proficiency of the user. Based on learner responses, Birdbrain uses an algorithm to instantly select new exercises for the next lesson. In other words, BirdBrain is consistently personalizing Duolingo’s lessons for its language learners. Birdbrain estimates the difficulty of each exercise by calculating the difficulty of its various components and when a learner gets an exercise wrong, Birdbrain lowers the estimate of the user’s ability and raises the estimate of the exercise’s difficulty. Birdbrain helps Duolingo accomplish the very difficult task of both challenging its learners while keeping them motivated to continue the lesson. (And I can can vouch for its success personally.)

In their article, the builders of Birdbrain explain their AI system in detail and outline the daunting challenges they’ve faced in updating and scaling their work. Along the way, they outline Duolingo’s history and mission and how educational psychology has influenced the app.

I’d encourage you to read the full article at IEEE Spectrum.