SEARCH

SEARCH BY CITATION

Keywords:

  • forensic science;
  • psychological stress;
  • deception;
  • speech;
  • voice stress;
  • phonetics

Abstract:  The purpose of this study was to evaluate a commonly used voice stress analyzer, the National Institute of Truth Verification’s (NITV) Computer Voice Stress Analyzer (CVSA), using a speech database containing materials recorded (i) in the laboratory, while highly controlled deceptive and shock-induced stress levels were systematically varied, and (ii) during a field procedure. Subjects were 24 each males/females (age range 18–63 years) drawn from a representative population. All held strong views on an issue and were required to make sharply derogatory statements about it. The CVSA system was then evaluated in a double-blind study using three sets of examiners: (i) two UF scientists trained/certified by NITV in CVSA operation, (ii) three experienced NITV operators provided by the manufacturer and (iii) five experimental phoneticians. The results showed that the “true positive” (or hit) rates for all examiners ranged from chance to somewhat higher levels (c. 50–65%) for all conditions and types of materials (e.g., stress vs. unstressed, truth vs. deception). However, the false-positive rate was just as high – often higher. Sensitivity statistics demonstrated that the CVSA system operated at about chance level.