Among the many peculiarities of schizophrenics perhaps the most obvious is their tendency to say odd things. Indeed, for most clinicians, the hallmark of schizophrenia is “thought disorder”. Decades of clinical observations, experimental research, and linguistic analyses have produced many hypotheses about what, precisely, is wrong with schizophrenic speech and language. These hypotheses range from assertions that schizophrenics have peculiar word association hierarchies to the notion that schizophrenics are suffering from an intermittent form of aphasia. In this article, several popular (...) hypotheses are critically assessed. Work in the area turns out to be flawed by errors in experimental method, faulty observations, tautological reasoning, and theoretical models that ignore the complexities of both speech and language. This does not mean that schizophrenics are indistinguishable from nonschizophrenics. They are clearly deviant in many situations. Their problem, however, appears to be in processing information and in selective attention, not in language itself. (shrink)

Decision making is the physician's major activity. Every day, in doctors' offices throughout the world, patients describe their symptoms and com plaints while doctors perform examinations, order tests, and, on the basis of these data, decide what is wrong and what should be done. Although the process may appear routine-even to the physicians in volved-each step in the sequence requires skilled clinical judgment. Physicians must decide: which symptoms are important, whether any laboratory tests should be done, how the various items (...) of clinical data should be combined, and, finally, which of several treatments (including doing nothing) is indicated. Although much of the information used in clinical decision making is objective, the physician's values (a belief that pain relief is more important than potential addiction to pain-killing drugs, for example) and subjectivity are as much a part of the clinical process as the objective findings of laboratory tests. In recent years, both physicians and psychologists have come to realize that patient management decisions are not only subjective but also prob abilistic (although this is not always acknowledged overtly). When doc tors argue that an operation is fairly safe because it has a mortality rate of only 1 %, they are at least implicitly admitting that the outcome of their decision is based on probability. (shrink)

A semantic network or net is a graphic notation for representing knowledge in patterns of interconnected nodes and arcs. Computer implementations of semantic networks were first developed for artificial intelligence and machine translation, but earlier versions have long been used in philosophy, psychology, and linguistics. What is common to all semantic networks is a declarative graphic representation that can be used either to represent knowledge or to support automated systems for reasoning about knowledge. Some versions are highly informal, but other (...) versions are formally defined systems of logic. Following are six of the most common kinds of semantic networks, each of which is discussed in detail in one section of this article. 1. Definitional networks emphasize the subtype or is-a relation between a concept type and a newly defined subtype. The resulting network, also called a generalization or subsumption hierarchy, supports the rule of inheritance for copying properties defined for a supertype to all of its subtypes. Since definitions are true by definition, the information in these networks is often assumed to be necessarily true. (shrink)