When receiving advice from multiple advisors, judges tend to rely more on aggregated advice (e.g., the mean of several estimates) than on non-aggregated advice (e.g., multiple individual estimates). The present work investigates why aggregated advice is heeded more strongly in judgment processes. Study 1 (N = 280) aimed to replicate the effect of advice presentation format and tested a proposed explanatory mechanism. We hypothesized that judges underestimate the diversity of advisors' opinions when receiving aggregated advice, which leads them to perceive aggregated advice as a stronger signal for adjustment. In a between-subjects design, participants received either aggregated or non-aggregated advice and, orthogonally, information about the actual range of advisors' estimates. Results replicated the higher utilization of aggregated advice and confirmed that the effect was attenuated when the range of opinions was explicitly displayed. Study 2 (N = 284) examined this proposed mechanism directly by testing whether the underestimation of advisors' range of opinions mediates the increased use of aggregated advice. In a within-subjects design, participants received both aggregated and non-aggregated advice across several numerical judgment tasks. They additionally estimated the range of advisors' opinions after aggregated trials. Analyses confirmed higher advice taking and a significant underestimation of the actual range for aggregated advice. Together, these studies advance our understanding of cognitive processes in advice utilization and highlight how the perceived diversity of advisors' opinions shapes the integration of multiple social inputs in judgment and decision-making.