Locust swarms can extend over hundred kilometers, and starvation compels this ancient pest to devour everything in its path. Theory suggests that gregarious behavior benefits foraging efficiency, yet the role of social cohesion remains elusive. To this end, we collected high-resolution trajectories of individual and grouped gregarious desert locusts in a 2-choice assay with patches of either similar or different quality. Carefully maintaining animals' identities allowed us to monitor each individual's experience and estimate the leaky accumulation process of personally acquired and socially derived evidence. We fitted data to a Bayesian model to gain insight into the decision-making system for patch selection. By disentangling the relative contribution of each information class, our study suggests that locusts balance incongruent evidence but reinforce congruent ones. We provide insight into the collective foraging decisions of social (but non-eusocial) insects and present locusts as a powerful empirical system to study individual choices and consequent collective dynamics.