The effects of prior expectations and outcome knowledge on polygraph examiners' decisions

Abstract

The present study deals with the question of whether judgments made by experts working in familiar contexts are affected by prior expectations and beliefs. Two experiments in which prior expectations were manipulated were designed to determine whether and to what extent polygraph examiners are affected by their prior expectations when analyzing and interpreting polygraph charts. Prior expectations affected the examiners' judgments when the polygraph charts did not include clear indications of guilt or innocence, but when the objective physiological evidence included strong indications which clearly contradicted the examiner's expectations, judgments were not affected by these expectations. Theoretical and practical implications of these results are discussed.

Why confessions trump innocence.

“…In one study, Elaad, Ginton, and Ben-Shakhar (1994) asked polygraph examiners from the Israeli Police Force to evaluate and interpret charts previously deemed inconclusive. Some examiners, but not others, were told that the suspect had ultimately confessed.…”

Deception detection with behavioral, autonomic, and neural measures: Conceptual and methodological considerations that warrant modesty

“…But what do such field studies look like? Research has shown that prior information about the guilt of a suspect-for example, about a confession-influences the outcomes of subsequent forensic tests, including the outcomes of lie detection tests (e.g., Bogaard, Meijer, Vrij, Broers, & Merckelbach, 2014;Elaad, Ginton, & Ben-Shakhar, 1994;Kassin, Dror, & Kukucka, 2013). Given the large number of degrees of freedom, especially when it comes to interpreting fMRI data, analysis of deception detection results may be prone to biasing observer effects.…”

Seek and ye shall find: test results are what you hypothesize they are

“…The present study, both in its conception and in its results, extends an earlier paper by Elaad, Ginton and Ben-Shakhar (1994). In that study, expert polygraph examiners were given inconclusive polygraph charts for interpretation and scoring.…”