Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving a plurality of answers to a first set of questions. The actions include generating an adjacency matrix based on the question-answer pairs. The actions include determining a network graph that includes question nodes and edges. The actions include identifying one or more clusters of question nodes by applying a community detection algorithm on the network graph. The actions include determining, for each cluster, i) a cluster centrality and ii) a cluster magnitude. The actions include ranking the clusters based on the cluster centralities and the cluster magnitudes of the one or more clusters. The actions include selecting a second set of questions for the user. And, the actions include causing the questions from the second set of questions to be presented to the user.