CACHE is a system supporting collaborative analysis tasks. We describe CACHE and a study of the effects of its use on reducing confirmation bias in analysis—the tendency to seek information that confirms rather than refutes an initial belief. We compare collaborative vs individual (Nominal) use of CACHE, as well as groups made of members with diverse (Heterogeneous) beliefs vs Homogeneous beliefs. We found reduction in confirmation bias for Heterogeneous collaborative groups using CACHE and working alone, but Homogeneous groups accentuated initial biases, rather than debiasing. Benefits of CACHE, future extensions, and our perspective on design are discussed.