Diagram showing a profile of a human head with areas labeled for placing electrodes to measure three types of electrical activity. Two dots at the top of the head and above the ear are labeled electroencephalogram (EEG) to measure brain waves. A pattern of long deflections representing an EEG printout is shown. Two dots on the eyelid and at the corner of the eye are labeled electrooculogram (EOG) to measure eye movements. A pattern of short deflections representing an EOG printout are shown. Two dots under the front and side of the chin are labeled electromyogram (EMG) to measure muscle tension. A series of very short deflections representing an EMG printout are shown.