Human-Activity Kinetic Alignment (HAKA)

A method for identifying a group of users from a number of users includes receiving, for each user of the number of users, response data including motion data characterizing motion of the user during a prescribed time period occurring after issuance of a challenge to the number of users, processing the motion data of the number of users to identify a first subset of the number of users with substantially matching motion data, and forming the group of users to include the first subset of the number of users.