Human languages have many properties that seem surprising from the perspective of communication: they are ambiguous, redundant, and apparently arbitrary. **Richard Futrell**, a PhD student in Cognitive Science at MIT, will discuss the remarkable variations among languages: some languages require you to mark gender all the time; in other languages never. In some languages you can rearrange words in whatever order you like, whereas in others, such as English, you can’t. Surprisingly, many of the universal properties of languages and the range of arrangements in particular languages can be predicted by assuming that languages are efficient and robust communication systems. Futrell explains how this recent line of research works, and what it can tell us about language and the human mind.