The present study provides a first attempt to compare the validity of the respiration line length (RLL) and skin resistance response (SRR) amplitude in real-life criminal guilty knowledge tests (GKTs). GKT records of 40 innocent and 40 guilty Ss, for whom actual truth was established by confession, were assessed for their accuracy. When a predefined decision rule was used and inconclusive decisions were excluded, 97.4% of the innocent Ss and 53.3% of the guilty Ss were correctly classified with the SRR measure. For the RLL measure, the respective results were 97.2% and 53.1%. The combination of both measures improved detection of guilty Ss to 75.8% and decreased detection of innocent Ss to 94.1%. The combined measure seems to be a more useful means of identifying guilty suspects than each physiological measure alone. The results elaborate and extend those obtained in a previous field study conducted by Elaad (1990).

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.

An experiment was designed to demonstrate the latent inhibition phenomenon in adult humans and to determine the effects of initial level of attention to the to-be-conditioned stimulus during a preexposure phase on subsequent learning. Results indicate that a strong latent inhibition effect can be obtained with adult humans. This effect occurs even though the preexposed stimulus is presented under severe conditions of inattention.