Experiment 2: BCI communication system for free conversation. (a) Two experienced participants used an asynchronous messaging interface to have an unprompted free conversation using a system with only six electrodes. This image was created by Dr David J. Lloyd. (b) The keyboard layout was similar to Experiment 1. The interface additionally included an electromyography (EMG) enter key [↵], controlled by detecting jaw clench signals at a frontal scalp electrode, allowing the participants to complete their messages, view the messaging display and recommence BCI typing. (c) BCI messaging display. The local participant’s (P1′s) messages are indicated with light blue, and the remote participant’s (P2′s) with light grey. The chat icon is enabled (bottom left corner), indicating that P2 is currently BCI typing, rather than viewing messages. (d) Three parallel threads devoted to reading the EEG, real-time analysis and stimulus presentation (indicated by rounded boxes). Inter-thread communication was via parallel port and TCP/IP (indicated by arrows). “Message” indicated the BCI typed text, and “status” indicated whether the remote participant was typing or viewing messages. The flow of information between threads was identical for P2.