I am a computer scientist with an interest in neuroscience. My research concerns problems at the boundary between people and computers. This involves investigating new technologies to enhance communication between computers and their users, and new applications to exploit these technologies. The main focus for this is human-computer interaction, where I have been leading work for some years on the use of video and paper as part of the user interface. The idea is to develop augmented environments in which everyday objects acquire computational properties through user interfaces based on video projection and digital cameras. Recent work has included desk-size projected displays and inference of users' mental states from facial expressions, speech, posture and gestures.