His research in human-computer interaction focuses on building interactive systems that support interaction at scale: crowdsourcing and human computation, online education and learning at scale, civic engagement and collective action, and interactive data analytics and mining. He creates interactive and collaborative technology that empowers conventionally passive populations -- students receiving instruction and citizens influenced by social issues -- to be active and self-directed participants who initiate deeper learning and collective action. He often takes an interdisciplinary approach to his research, by connecting computer science with learning sciences and social sciences, and aims to deploy interactive systems to real users.