Carnap's inductive probabilities as a contribution to decision theory

Common probability theories only allow the deduction of probabilities by using previously known or presupposed probabilities. They do not, however, allow the derivation of probabilities from observed data alone. The question thus arises as to how probabilities in the empirical sciences, especially in medicine, may be arrived at. Carnap hoped to be able to answer this question byhis theory of inductive probabilities. In the first four sections of the present paper the above mentioned problem is discussed in general. After a short presentation of Carnap's theory it is then shown that this theory cannot claim validity for arbitrary random processes. It is suggested that the theory be only applied to binomial and multinomial experiments. By application of de Finetti's theorem Carnap's inductive probabilities are interpreted as consecutive probabilities of the Bayesian kind. Through the introduction of a new axiom the decision parameter λ can be determined even if no a priori knowledge is given. Finally, it is demonstrated that the fundamental problem of Wald's decision theory, i.e., the determination of a plausible criterion where no a priori knowledge is available, can be solved for the cases of binomial and multinomial experiments.     

Implicit and self-attributed motives to achieve: two separate but interacting needs

This research examined how implicit and self-attributed needs to achieve (labeled as n Ach and san Ach, respectively) combine with self-referenced and norm-referenced feedback to predict effort-related (task performance) and choice-related (task continuation) indexes of students' engagement in a mental concentration task. In Experiment 1 the authors found that in a task-focused setting, task performance was predicted by the joint effect of self-referenced feedback and n Ach, whereas task continuation was predicted by the joint effect of norm-referenced feedback and san Ach. In Experiment 2 the authors found that in an ego-focused setting, n Ach and san Ach interacted in the prediction of task performance but not of task continuation. In Experiment 3 the authors found that the effects of n Ach and san Ach on students' performance were mediated by the anticipated affective value of achievement outcomes. These findings are discussed in relation to a 2-system approach to achievement motivation.     

Visual analysis of changes of motion in reaction-time tasks

Subjects observed a random-dot pattern moving uniformly in the vertical direction (vector V1). The motion vector abruptly changed to V2, both in speed and direction simultaneously. It was found that the time of simple reaction to such changes V1 --> V2 can be described by a function of a single variable, [w(V1 - V2c) + (1 - w) V2N], 0 < w < 0.5, where V2c and V2N are the components of V2 collinear with and normal to V1. The choice-reaction time for changes in direction that are accompanied by changes in speed can be described by a function solely of the absolute value of V2N. Unlike the simple-reaction time, the choice-reaction time was independent of the initial speed of motion. The processes that may be engaged in simple and choice reactions to motion are discussed.     

The belief in a just world and distress at school

This article investigates the relationship between the belief in a just world (BJW) and distress at school. On the basis of just world theory, the authors argue that strong student BJW should be associated with low school distress. Two questionnaire studies with German secondary school students attending grades 7–13 are reported. Both studies found strong BJW to be associated with less distress at school, better grades, and the evaluation of grades and teachers as more just. Moreover, the relationship between strong BJW and low school distress persisted when controlled for grades, justice of grades, and teacher justice. This relationship held for all students, independently of their school track, grade level, or gender. Overall, the pattern of results reveals school distress to have a unique association with BJW and school-specific justice cognitions.     

Selecting spatial frames of reference for visual target localization

This study examined the selection of spatial frames of reference for target localization in visual search. Participants searched for local target characters in global character configurations. The local targets could be localized relative to the character configuration in which they were embedded or relative to the presentation screen on which the configurations were displayed. We investigated under which conditions the configurations, or the screen served as frame of reference for target localization. Three experiments revealed an increasing impact of screen-related target localization with decreasing spatial uncertainty of targets in screen-related coordinates. The results indicate the capability of the visual system to localize relevant visual stimuli with respect to those frames of reference that yield the most redundant spatial distribution of these stimuli.     

What determines the detection of changes in motion velocity? A comment on Dzhafarov,Sekuler, and Allik (1993)

We comment on a recent model aimed at explaining data on speed of reaction to motion onset and to changes in motion velocity. The model is based on calculating the running variance of the stimulus positions passed during the motion. We show that although the model is successful in explaining data on motion onset and suprathreshold velocity changes, it may not be able to explain data on time of reaction to changes in velocity when these are near the detection threshold.     

Psychosis in German prisoners: Comparison of the clinical appearance of psychotic disorder of an imprisoned population with a not detained community group

Surveys confirm risk factors for the incarceration of patients with psychosis including homelessness and comorbidity. There is also agreement that severe psychosis can lead to violence. Data describing prisoners with psychosis in Germany are scarce. We aimed to compare patients with psychosis in a prison hospital and patients with psychosis in a community hospital. Demographic data were collected, as well as comorbidity in the form of substance dependence and a psychiatric assessment using the German version of the 18-item Brief Psychiatric Rating Scale (BPRS) and the Positive and Negative Syndrome Scale (PANSS). In the prison hospital group more patients were homeless (17 versus 2%) and non-German (36 versus 4%). There were also more patients with substance dependence or abuse in the prison hospital group. The total scores of BPRS and PANSS were lower in the prison hospital group (BPRS, 43.8 versus 51.2; PANSS, 71.5 versus 83.7). We assume that social disintegration for mentally disturbed offenders prior to incarceration hindered effective treatment. To avoid further social disintegration and possible further deterioration of mental health status of released offenders, which may lead to reoffending after imprisonment, discharge management after release from prison should be improved.