If you have ever completed a Captcha security verification test on a computer or are learning a foreign language on the Duolingo app (options include Spanish, Korean or High Valyrian from Game of Thrones), then you probably have an immigrant called Luis von Ahn to thank for the experience. Born in Guatemala City, von Ahn moved to the US for university and has built his career in the country. As a computer scientist at Carnegie Mellon University, he created the reCaptcha squiggly-letter fraud protection test bought by Google in 2009. He then founded Duolingo, which now employs 600 people and has a stock market value of $3.1bn.
