Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving brain activity data of a user from a brainwave sensor and user physiological data from a non-brainwave sensor, where the brain activity data represents a brainwave pattern related to a physiological activity of the user and a brainwave pattern related to a mental activity of the user. Identifying a physiological action of the user based on the user physiological data. Identifying, within the brain activity data, a pattern that is representative of the identified physiological action. Filtering the brain activity data to lessen a contribution of the pattern representative of the identified physiological action to the brain activity data, thereby, providing filtered brain activity data.