refer to a thing and stephen jay gould and others have criticized psychologists for doing just that. one critic states that "instead of replacing 'metaphysical' terms such as 'desire' and 'purpose', they used it to legitimize them by giving them operational definitions. thus in psychology, as in economics, the initial, quite radical operationalist ideas eventually came to serve as little more than a 'reassurance fetish' (koch 1992, 275) for mainstream methodological practice." according to tadafumi kato, since the era of kraepelin, psychiatrists have been trying to differentiate mental disorders by using clinical interviews. kato argues there has been little progress over the last century and that only modest improvements are possible in this way; he suggests that only neurobiological studies using modern technology could form the basis for a new classification. according to heinz katsching, expert committees have combined phenomenological criteria in variable ways into categories of mental disorders, repeatedly defined and redefined over the last half century. the diagnostic categories are termed "disorders" and yet, despite not being validated by biological criteria as most medical diseases are, are framed as medical diseases identified by medical diagnoses. he describes them as top-down classification systems similar to the botanic classifications of plants in the 17th and 18th centuries, when experts decided a priori which visible aspects of plants were relevant. katsching notes that while psychopathological phenomena are certainly observed and experienced, the conceptual basis of psychiatric diagnostic categories is questioned from various ideological perspectives. psychiatrist joel paris argues that psychiatry is sometimes susceptible to diagnostic fads. some have been based on theory (overdiagnosis of schizophrenia), some based on etiological (causation) concepts (overdiagnosis of post-traumatic stress disorder), and some based on the development of treatments. paris points out that psychiatrists like to diagnose conditions they can treat, and gives examples of what he sees as prescribing patterns paralleling diagnostic trends, for example an increase in bipolar diagnosis once lithium came into use, and similar scenarios with the use of electroconvulsive therapy, neuroleptics, tricyclic antidepressants, and ssris. he notes that there was a time when every patient seemed to have "latent schizophrenia" and another time when everything in psychiatry seemed to be "masked depression", and he fears that the boundaries of the bipolar spectrum concept, including in application to children, are similarly expanding. allen frances has suggested fad diagnostic trends regarding autism and attention deficit hyperactivity disorder. since the 1980s, psychologist paula caplan has had concerns about psychiatric diagnosis, and people being arbitrarily "slapped with a psychiatric label". caplan says psychiatric diagnosis is unregulated, so doctors aren't required to spend much time understanding patients situations or to seek another doctor's opinion. the criteria for allocating psychiatric labels are contained in the diagnostic and statistical manual of mental disorders, which can "lead a therapist to focus on narrow checklists of symptoms, with little consideration for what is causing the patient's suffering". so, according to caplan, getting a psychiatric diagnosis and label often hinders recovery. the dsm and icd approach remains under attack both because of the implied causality model and because some researchers believe it better to aim at underlying brain differences which can precede symptoms by many years.