Confirmation Bias in Complex Analyses

By Brant Cheikes , Mark Brown , Dr. Paul Lehner , Dr. Leonard Adelman

Most research investigating the confirmation bias involves abstract experimental tasks where subjects draw inferences from just a few items of evidence.

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Most research investigating the confirmation bias involves abstract experimental tasks where subjects draw inferences from just a few items of evidence. These tasks are not representative of complex analysis tasks characteristic of law enforcement investigations, financial analysis and intelligence analysis. This study examines the confirmation bias in a more complex analysis task and evaluates a recommended procedure, called Analysis of Competing Hypotheses (ACH), designed to mitigate confirmation bias. Results indicate that participant assessment of new evidence was significantly impacted by beliefs they held at the time evidence was received. Evidence confirming current beliefs was given more "weight" than disconfirming evidence. However, current beliefs did not influence the assessment of whether an evidence item was confirming or disconfirming. ACH did reduce confirmation bias, but the effect was limited to participants without professional analysis experience.