Polygraphs are instruments that measure physiological responses (respiration, pulse, blood pressure, and galvanic resistance) to stress. Among other purposes polygraphs are used to help determine an individual’s eligibility for a special assignment or access to specifically designated information protected within SAPs. They are not generally used for collateral security clearances, unless they are necessary to resolve serious credible derogatory information that cannot be resolved through conventional investigative means. Polygraph examinations are conducted as a supplement to, not as a substitute for, other forms of investigation that may be required under the circumstances. Polygraph exams are only administered by agencies with approved personnel security polygraph programs and these exams are only conducted by government trained and certified examiners.