Electrical signals originating in the brain are measured and analyzed. In one embodiment, this technology serves to assess brain functioning as a means to evaluate cognitive functioning, to detect cognitive deficits such as those brought about by Alzheimer's, and to assess the efficacy of treatments for cognitive disorders. In another embodiment, which is an improvement on technology previously patented by the inventor, this technology serves to detect information in the brain as a means of detecting participation in specific organizations, acts, or criminal activity. In a third embodiment, this technology serves to evaluate the effectiveness of advertising, educational and training presentations by detecting the attention, information processing, and memory-related responses to these presentations as revealed by brain waves.