The cumulative research evidence suggests that CQTs detect deception better than chance, but with significant error rates, both of misclassifying innocent subjects (false positives) and failing to detect guilty individuals (false negatives).
Research on the processes involved in CQT polygraph examinations suggests that several examiner, examinee, and situational factors influence test validity, as may the technique used to score polygraph charts.
Rate and depth of respiration are measured by pneumographs wrapped around a subject's chest.
Cardiovascular activity is assessed by a blood pressure cuff.
Lie detector tests have become a popular cultural icon — from crime dramas to comedies to advertisements — the picture of a polygraph pen wildly gyrating on a moving chart is readily recognized symbol.