"Part of Duolingo's success is their unorthodox approach to online learning: Much like online games and e-commerce sites, Duolingo uses A/B testing to hone their curriculum. The small but crucial difference is that Duolingo doesn't use A/B testing--giving different users slightly different online experiences for the purpose of testing--to sell more consumer products or in-game currency. Alongside standard web design tweaking, von Ahn and his team use A/B testing to find different ways people learn languages--and tweak Duolingo's experiences based on that." - × × ×