an information handling method in which information items are mapped to respective nodes in an array of nodes by mutual similarity of the information items , such that similar information items map to nodes at similar positions in the array of nodes ; there being a mapping relationship between frequencies of occurrence , within an information item , of each of a concordance of information features and nodes in the array of nodes , comprises the steps , in respect of an information item to be processed , of : detecting a closest node in the array of nodes , the closest node being that node for which the mapping relationship provides a closest match with the information item to be processed ; selecting a group of nodes near , in the array , to the closest node ; and modifying the mapping relationship so that the closest node and the group of nodes are brought generally closer to the information item to be processed ; in which , for the purposes of selecting the group of nodes , the array wraps around so that a peripheral edge of the array is treated as adjacent to an opposite peripheral edge of the array .