An information retrieval system in which a set of distinct information items map to respective nodes in an array of nodes by mutual similarity of the information items, so that similar information items map to nodes at similar positions in the array of nodes; comprises a search arrangement for selecting a subset of the information items by applying a user-defined search query against the information items, the search arrangement being operable to detect a degree of relevance of each information item in the subset to the search query; and a graphical user interface for displaying a representation of those nodes corresponding to at least some of the subset of information items as a two-dimensional display array of display points within a node display area on a user display; the graphical user interface being operable to display the display points with respective display properties dependent on the detected degree of relevance of the corresponding information item.