Duolingo's unabashed gamification

How it works: Duolingo has A/B tested its way to a highly addictive app, in a successful attempt to solve the biggest problem in language learning, which is that people aren't motivated to spend enough time doing it.

• The catch: The way to get people to spend more time on the app might not be the best way to get them to learn a language. Burr Settles, Duolingo's director of research, told Natasha Mascarenhas of TechCrunch that users spend more time on the app whenever it gets easier.
• "Ultimately, when the product team has to make a decision between engagement and learning efficacy, it typically must err toward entertainment over education," writes Mascarenhas.