Jurors’ verdicts based on their intimate conviction: Influence of magistrate’s opinion on confirmatory information processing

Abstract

A large body of research has focused on legal decision-making. However, few studies have tested the impact on evidence processing of the intimate conviction (IC) instruction, a decision rule based on impression formation that is used in mixed courts of lay and professional judges in civil law systems. The present study examined 1) the influence of the IC instruction (vs. induction of rational information processing) on confirmatory information processing (CIP) in a judicial judgment context, and 2) the impact of a professional judge (i.e., magistrate)’s pro-accusation (vs. pro-defense) opinion prior to the deliberation phase on lay jurors’ CIP under impression (vs. rational) induction. Sixty-nine mock jurors (students) watched video extracts of a criminal appeal hearing of a harm-to-person case. Results confirmed our prediction: in the pre-deliberation phase, participants who had been given an impression decision rule exhibited a stronger pro-accusation CIP bias (biased assimilation, but not selective exposure); in the post-deliberation phase, impression induction only enhanced CIP bias when the jurors agreed with the magistrate’s opinion, whereas rational induction only enhanced CIP bias when the jurors disagreed with the magistrate’s opinion. These results are discussed in terms of psychological reactance in the context of decision-making processes.