It is suggested that schizophrenic thinking can be explained as a lowering of levels of significance for acceptance of conclusions based on inductive logic. The formal similarity between inductive logic and operant, or classical conditioning is pointed out. It is thus possible to explain the therapeutic effects of neuroleptic drugs by referring to the effect of these, and related drugs, and of lesions of ascending dopamine pathways, on acquisition of conditioned responses. It is tentatively suggested that recognition of association of related features of the environment, whether in humans or animals occurs in the basal ganglia by a dopamine dependent process. A role is suggested for neocortical noradrenaline in consolidaton of newly acquired associations. Implications and tests of this hypothesis are discussed.