From the moment they make up their mind, people are reluctant to change it. We tested the hypothesis that people disposing of more cognitive resources—through circadian variations or socially distributed thinking—would engage in deliberative thinking and would consequently be less likely to exhibit belief perseverance. Perseverance was measured by the change in judgments related to a suspect in a criminal case, following the presentation of an offender profile that was at odds with the suspect’s description. Individuals tested at a compatible circadian time exhibited less perseverance in the face of contradictory evidence compared to individuals tested at an incongruent time. Individuals deliberating on their own also tended to show more belief perseverance compared to those who worked in groups. There was, however, no interaction effect between circadian timing and condition of deliberation on belief change. The implications for our understanding of the mechanisms that underpin belief perseverance are discussed.