Other critical psychiatrists argue that just because a persons belief is unshaken by one influence does not prove that it would remain unshaken by another. For example, a person whose beliefs are not changed by verbal correction from a psychiatrist, which is how delusion is usually diagnosed, may still change his or her mind when observing empirical evidence, only that psychiatrists rarely, if ever, present patients with such situations.Anthropologist David Graeber have criticized psychiatrys assumption that an absurd belief goes from being delusional to "being there for a reason" merely because it is shared by many people by arguing that just as genetic pathogens like viruses can take advantage of an organism without benefitting said organism, memetic phenomena can spread while being harmful to societies, implying that entire societies can become ill. David Graeber argued that if somatic medicine did not have higher scientific standards than psychiatrys way of defining delusion, pandemics like the plague would have been considered to transsubstantiate from an illness to "a phenomenon that benefits the people" as soon as it had spread to a sufficiently large portion of the population.
In other cases, the belief may be mistakenly assumed to be false by a doctor or psychiatrist assessing it, just because it seems to be unlikely, bizarre or held with excessive conviction. Psychiatrists rarely have the time or resources to check the validity of a persons claims leading to some true beliefs to be erroneously classified as delusional. This is known as the Martha Mitchell effect, after the wife of the attorney general who alleged that illegal activity was taking place in the White House. At the time, her claims were thought to be signs of mental illness, and only after the Watergate scandal broke was she proved right (and hence sane). Similar factors have led to criticisms of Jaspers definition of true delusions as being ultimately un-understandable. Critics (such as R. D. Laing) have argued that this leads to the diagnosis of delusions being based on the subjective understanding of a particular psychiatrist, who may not have access to all the information that might make a belief otherwise interpretable. R. D. Laings hypothesis has been applied to some forms of projective therapy to "fix" a delusional system so that it cannot be altered by the patient. Psychiatric researchers at Yale University, Ohio State University and the Community Mental Health Center of Middle Georgia have used novels and motion picture films as the focus. Texts, plots and cinematography are discussed and the delusions approached tangentially.