Head size in relation to schizophrenia and schizotypy.

Cranial breadth and length on DSM-III schizophrenic probands (n = 16) and their nonpsychotic siblings (n = 34) were measured using standard anthropometric calipers. Siblings were divided into those with and those without DSM-III schizotypal personality disorder based on Baron et al.'s Schedule for Schizotypal Personalities interview (1981). These siblings provide controls for prenatal and childhood nutritional status, which could affect head size, and for genetic contributors to head size. Contrary to previous reports (Andreasen et al. 1986; and Pearlson et al. 1989), in the present sample schizophrenic patients did not have smaller heads. The relationship between height and head size for schizophrenic subjects, schizotypal siblings, and nonschizotypal siblings was also examined. As in Andreasen et al. (1986), the regression slope of head size on height was lower in schizophrenic patients than in their siblings, but here this difference was not significant. The data do not support a conjectured relationship between small or dysmorphic head size and schizophrenia or schizotypy.

Familial prevalence and coaggregation of schizotypy indicators: a multitrait family study.

Schizophrenic probands (n = 17), their first-degree relatives (n = 61), and medically and psychiatrically screened normal control subjects (n = 18) were studied with structured interviews for DSM-III Axis I disorders and schizotypal personality disorder, questionnaire measures of schizotypy, measures of smooth-pursuit eye movement dysfunction, and attention dysfunction. Schizophrenic subjects scored abnormally on essentially all measures. Relatives differed significantly from control subjects on most measures. Correlational analyses indicate that many characteristics tested in these measures run together in families. The data are consistent with the hypothesis that a single vulnerability dimension or typology, presumably in part genetically transmitted, may account for phenotypically distinct abnormalities. These traits, taken together, may have joint usefulness for identifying persons with a predisposition to schizophrenia.

Clinical versus mechanical prediction: a meta-analysis.

The process of making judgments and decisions requires a method for combining data. To compare the accuracy of clinical and mechanical (formal, statistical) data-combination techniques, we performed a meta-analysis on studies of human health and behavior. On average, mechanical-prediction techniques were about 10% more accurate than clinical predictions. Depending on the specific analysis, mechanical prediction substantially outperformed clinical prediction in 33%-47% of studies examined. Although clinical predictions were often as accurate as mechanical predictions, in only a few studies (6%-16%) were they substantially more accurate. Superiority for mechanical-prediction techniques was consistent, regardless of the judgment task, type of judges, judges' amounts of experience, or the types of data being combined. Clinical predictions performed relatively less well when predictors included clinical interview data. These data indicate that mechanical predictions of human behaviors are equal or superior to clinical prediction methods for a wide range of circumstances.