The reverse learning theory says that as we learn and grow, connections are made in our neocortex in a semirandom way. As the number of connections increases, the network becomes less and less efficient. If there were no mechanism to control the number of connections, "parasitic" memories - memories that combine parts of real memories and are falsely associated with many different inputs - would develop eventually. Crick and Mitchison predicted that if this were to happen, people might develop bizarre thoughts (from mixed up memories), hallucinations (from memories being associated with the wrong inputs) or obsessions (from the same connections being made over and over).