1. A method of monitoring individual performance, comprising: measuring an objective data parameter corresponding to a first aspect of a subject; collecting a subjective data parameter corresponding to a second aspect of the subject by way of a user interface; and determining a cognitive effectiveness level of the subject based at least on the objective and subjective data parameters; wherein the subjective data parameter is a data parameter representative of a subject's manual indication of a subjective mental state, the subjective mental state including a wake state.