How we update our beliefs when encountering new evidence is the basis of evidential reasoning. Often, this will involve weighing up multiple pieces of evidence communicated to us by several sources (i.e., testimony). However, the testimonies of multiple sources are rarely truly independent; they may have used the same data or evidence, have the same training or background, or simply be repeating the same story as another. The nature of these dependencies among our evidence items is normatively impactful on the conclusions we should draw. Here we investigate whether participants are sensitive to such complex, yet impactful influences on their reasoning. We find a general preference for source diversity that heuristically gels with normative assertions. To our knowledge, it is the first paradigm that integrates shared background, shared evidence, and corroboration in the same design. We discuss challenges with developing and testing the intricacies of this.