Psychopathologists have tended to regard the phenomena of schizophrenic language as reflections of a more basic disturbance of thought. Writings on these topics generally link them together (e.g., Kasanin's Language and Thought in Schizophrenia, 1944). Critchley (1964), from his survey of major aspects of psychotic speech, concluded that the ‘causation of schizophrenic speech affection lies in an underlying thought disorder, rather than in a linguistic inaccessibility’. Differences of opinion are evident as to what the nature of this thinking disorder might be. Regression (Gardner, 1931; Kasanin, 1944), excessive concreteness of thought (Goldstein, 1944; Milgram, 1959) and deficiency in logical deductive reasoning (Von Domarus, 1944) are some of the more prominent hypotheses to be found in the literature relating to this problem.