In the present study, the authors examined the effects of outside issues on the validity of the Comparison Question Test in a laboratory mock-crime paradigm. In a 2 × 2 X 2 factorial design, 192 participants either did or did not commit (a) a mock theft of a dollar (about which they were tested), or (b) a mock theft of $20 (the outside issue); and they either were or were not asked questions about an outside issue. The presence of the outside issue had a strong differential impact on the participants who were innocent of the tested issue, and it dramatically moved their scores toward deception. The impact of an outside issue on the guilty was minimal. Test questions about possible outside issues were ineffective in detecting the presence of the outside issue, but they did function as comparison questions. The results have implications for understanding the high rate of false positive outcomes in some studies.
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