Have a person sit, relaxed, in a softly-lit room. Don't tell the person the reason you are doing this test. Press the Start button and watch his or her eyes, counting the number of blinks. When you hear the alert, a full minute has passed. How many eye-blinks did you count? The normal rate is 15 blinks per minute. Significantly more blinks usually means the person is nervous about something. Significantly less could mean the person is in deep concentration, or is staring intently.