Brain damage can induce anomalous neuronal connections in experimental animals, which can sometimes result in maladaptive behaviour, particularly when damage occurs early in development. Anomalous patterns of neuronal connection can also arise from genetic disorders. In humans, neuronal misconnections could be involved in a variety of psychiatric disorders. For example, they may account for the link between hyperkinesis and childhood hemiplegia, and for the link between schizophrenia and 'alien tissue' lesions of the temporal lobes. Predictions from misconnection hypotheses can potentially be tested in neuropathological, neurophysiological, and clinical studies.