Abstract: Computer-implemented systems and methods are provided for determining indications of a mental state of a subject. A computing system may receive at least one electrophysiological signal from at least one pair of electrodes on a head of a subject. The system may store at least one threshold bio-electrical value, and compare a plurality of portions of the at least one electrophysiological signal with the stored value. The system may determine, based on the comparing, identities of portions of the at least one electrophysiological signal that surpass the stored at least one threshold bio-electrical value. The system may also determine the existence of a portion sequence among the portions of the at least one electrophysiological signal that surpass the stored at least one threshold bio-electrical value. And the system may output an indication of a mental state of the subject when it is determined that the portion sequence exists.