Previous work on information foraging theory has addressed how people navigate through information systems to find information. This paper presents a new information foraging model called InfoCLASS that models the conceptual categories that people learn while interacting with information systems. InfoCLASS is based on previous work on the rational analysis of human category formation. InfoCLASS simulations can be used to make qualitative predictions about the richness of conceptual categories that will be learned from different experiential histories, and from different kinds of user interfaces. InfoCLASS simulations can also be used to predict the conceptual consensus among a group of users of information systems. It is argued that the degree of conceptual coherence among a group of users is an important determinant of the efficiency and effectiveness of a social organization engaged in making discoveries, such as scientific communities.