Effect of altered outcome expectancies stemming from placebo and feedback treatments on the validity of the guilty knowledge technique

Abstract

Examined the effect of using placebo and feedback treatments to alter outcome expectancies on the detection efficiency of the guilty knowledge polygraph technique. 270 undergraduates each committed a mock murder, after which the investigator administered a series of 5 lie detector tests to ascertain the facts involved in the simulated murder. Prior to testing, an equal number of male and female Ss were randomly assigned to 1 of 9 treatment groups. The groups consisted of the different treatment combinations produced by pairing 1 of 3 placebo conditions (pass, control, fail) with 1 of 3 feedback conditions (pass, control, fail). Although highly significant sex and feedback effects on outcome expectancies were found, there were no significant main or interaction effects produced by the sex, feedback, or placebo conditions with respect to detection efficiency as measured by a standard guilty knowledge scoring procedure. Results support the detection of deception theories that stress the importance of differential arousal and/or habituation effects associated with relevant and irrelevant stimuli. (25 ref) (PsycInfo Database Record (c) 2025 APA, all rights reserved)