False positive, False negative – While the polygraph technique is highly accurate, it is not infallible and errors do occur. Polygraph errors may be caused by the examiner’s failure to properly prepare the examinee for the examination, or by a misreading of the physiological data on the polygraph charts. Errors are usually referred to as either false positives or false negatives. A false positive occurs when a truthful examinee is reported as being deceptive; a false negative when a deceptive examinee is reported as truthful. Some research indicates that false negatives occur more frequently than false positives, other research studies show the opposite conclusion. Since it is recognized that any error is damaging, examiners utilize a variety of procedures to identify the presence of factors which may cause false responses, and to insure an unbiased review of the polygraph records.