Some persons with schizotypal personality disorders go on to develop schizophrenia,[14] but most of them do not.[15] Although STPD symptomatology has been studied longitudinally in a number of community samples, the results received do not suggest any significant likelihood of the development of schizophrenia.[16] There are dozens of studies showing that individuals with schizotypal personality disorder score similar to individuals with schizophrenia on a very wide range of neuropsychological tests. Cognitive deficits in patients with schizotypal personality disorder are very similar to, but quantitatively milder than, those for patients with schizophrenia.[17] A 2004 study, however, reported neurological evidence that did "not entirely support the model that SPD is simply an attenuated form of schizophrenia".[18]