POLYGRAPHS

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POLYGRAPHS
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• WHO USES THEM?
• PRIVATE EMPLOYERS ARE THE BIGGEST USER
• USE IN CRIMINAL INVESTIGATIONS IS SECOND MOST
  COMMON USAGE
• FEDERAL GOVERNMENT IS THIRD BIGGEST USER

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• HOW IT WORKS
• FOUR SENSORS MEASURE BREATHING, BLOOD PRESSURE,
  HEART RATE, AND PERSPIRATION--ALL SIGNS OF
  AROUSAL
• CONTROL QUESTION APPROACH
• GUILTY KNOWLEDGE TEST

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• ACCURACY DEPENDS ON
• EXAMINER BIASES AND SKILLS
• PROFESSIONAL POLYGRAPHERS HAVE VESTED INTEREST IN
  ADVERTISING HIGH DETECTION RATES
• EXAMINERS SKILL IN QUESTIONING
• EXAMINERS SKILL IN READING THE PHYSIOLOGICAL
  PROFILE
• MAY DETECT TRUTHTELLERS ALONG WITH LIARS--E.G.,
  IN EMPLOYMENT SCREENING, MANY NON-LIARS/CHEATERS
  ARE SCREENED OUT WITH THE LIARS/CHEATERS

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• NATURE OF THE LIE
• NATURE OF THE LIAR
• THEY CAN BE BEAT WITH DRUGS, BITING ONES TONGUE
  OR PUTTING A TACK IN YOUR SHOE, HYPNOSIS,
  RELAXATION, BIOFEEDBACK TRAINING
• KNOWING WHAT GROUND TRUTH IS

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• BOTTOM LINES
• THE POLYGRAPH IS PROBABLY MORE ACCURATE THAN MOST
  HUMAN DETECTORS, BUT TRAINED HUMANS CAN BE JUST
  AS ACCURATE
• POLYGRAPH RESULTS, LIKE THOSE OBSERVATIONS FROM
  BEHAVIORAL CUES, SHOULD BE COUCHED IN TERMS OF
  PROBABILITIES OF LYING ONLY