Competing and collaborating brains: multi-brain computer interfacing

In this chapter we survey the possibilities of brain-computer interface applications that assume two or more users, where at least one of the users’ brain activity is used as input to the application. Such ‘applications’ were already explored by artists who introduced artistic EEG applications in the early ‘seventies’ of the previous century. These early explorations were not yet sup-ported by advanced signal process methods, simply because there was no com-puting support possible, and interest in artistic applications faded until it reappeared in more recent years. Research in neuroscience, signal processing, ma-chine learning and applications in medical, assistive BCIs prevailed. It was sup-ported by computer science that provided real-time and off-line processing to analyze and store large amounts of streaming or collected data. With the possi-bility to access cheap shared and distributed storage and processing power, as it became available in the last decade of the previous century and the first decade of this century, different kinds of BCI applications, following a general interest in digital games, interactive entertainment and social media, became visible. These are domains where experience, fun and emotions are more important than efficiency, robustness and control. BCI provides user and application with a new modality that can be manipulated and interpreted, in addition to other input modalities. This has been explored, but mostly from the point of view of a single user interacting with an application. In this chapter we look at BCI applications where more than one user is involved. Games are among the possible ap-plications and there are already simple games where gamers compete or collab-orate using brain signal information from one or more players. We consider ex-tensions of current applications by looking at different types of multi-user games, including massively multi-player online role-playing games. We mention research - distinguishing between active and passive BCI - on multi-participant BCI in non-game contexts that provides us with information about the possibilities of collaborative and competitive multi-brain games and that allows us to develop a vision on such games. The results of the literature study are collected in a table where we distinguish between the various forms of interaction between players (participants) in collaborative and competitive games and team activities.