Schizophrenia may be described as a disease where speech, bodily language and social responsiveness are obvious expressions of a deteriorated ability to interact with the surroundings in a precise and relevant way. The lack of precision and relevance pertains to perception and recall as well as communication and action. The deficient potential for activation of the prefrontal cerebral cortex is a neurobiological correlate to the lesion of precise and relevant planning and expression. Impairment of formal thought and language in schizophrenia are suggested to result from a developmental disorder pertaining to language and concept formation (apperception). In reactive psychoses with dissociative disturbances of consciousness there is an inefficient capacity for adapting to external reality; thus relevant conscious planning and interaction with the outside world are impaired. Clinically a distractibility of a tematic nature ensues. Except for catastrophic events, psychotic reactions cannot be predicted from analysis of the actual experience--neither concerning the external nor the internal aspects of conscious awareness. Sometimes, however, previous events relating to the formation of the self may add explanatory value to the analysis of reactive psychosis. In some cases biological predisposition is the decisive determinant. The normal discrimination between sense-perception and imagination has a counterpart in the dichotomy of awareness of the outside world versus awareness of the self. The following are examples of psychotic experience where the normal ability for dichotomic discrimination may be damaged: Illusions of affect, hallucinations, Schneider's first rank symptoms, "Anwesenheit" and consciousness of time.(ABSTRACT TRUNCATED AT 250 WORDS)