Some exact results for random walk models with applications

This article presents a random walk model that can be analyzed without recourse to Wald's (1947) approximation, which neglects the excess over the absorbing barriers. Hence, the model yields exact predictions for the absorption probabilities and all mean conditional absorption times. We derive these predictions in some detail and fit them to the extensive data of an identification experiment published by Green et al. (1983). The fit of the model seems satisfactory. The relationship of the model to existing classes of random walk models (SPRT and SSR; see Luce, 1986) is discussed; for certain combinations of its parameters, the model belongs either to the SPRT or to the SSR class, or to both. We stress the theoretical significance of the knowledge of exact results for the evaluation of Wald's approximation and general properties of the several models proposed derived from this approximation.     

What triggers causal attributions? The impact of valence and subjective probability

Various field studies and experimental simulations demonstrated that causal reasoning increases after unexpected as well as after unpleasant events. However, unpleasant events are seen as less likely than pleasant ones in everyday life. Accordingly, the subjective probability of the event and its hedonic quality were naturally confounded in these studies. To isolate the contribution of both determinants, the subjective probability and the valence of an event were independently manipulated in a laboratory experiment. Subjects completed an ostensible ‘professional skills test’ and received either success or failure feedback in relation to a criterion set by the experimenter. The subjective probability of success was varied by informing subjects about the distribution of success and failure in a comparable population (either 23 per cent or 77 per cent were said to meet the criterion). The results indicate a pronounced valence effect: The intensity of causal reasoning and the number of possible reasons reported for the outcome was greater after negative than after positive feedback, independent of the a priori probability of the outcome. No evidence for an increase in causal explanations after unexpected, as compared to expected, events was obtained. Several mediating processes are discussed.     

Subjunctive Conditional Probability

There seem to be two ways of supposing a proposition: supposing “indicatively” that Shakespeare didn’t write Hamlet, it is likely that someone else did; supposing “subjunctively” that Shakespeare hadn’t written Hamlet, it is likely that nobody would have written the play. Let P(B//A) be the probability of B on the subjunctive supposition that A. Is P(B//A) equal to the probability of the corresponding counterfactual, A □→B? I review recent triviality arguments against this hypothesis and argue that they do not succeed. On the other hand, I argue that even if we can equate P(B//A) with P(A □→B), we still need an account of how subjunctive conditional probabilities are related to unconditional probabilities. The triviality arguments reveal that the connection is not as straightforward as one might have hoped.     

Positive Affect and College Success

This study investigated the relation between positive affect and a variety of variables related to college success for undergraduate students matriculating at 21 academically selective 4-year colleges and universities in the United States. Positive affect??cheerfulness??is generally positively related to students?? self-rated academic abilities, self-predicted likelihoods of various college outcomes, self-stated major and academic-degree intentions, and self-reported subjective college outcomes, but negatively related to most objective college-success variables (e.g., cumulative college grade-point average) recorded by the institution of matriculation, and not related to objective college outcomes reported by the student. Positive affect is thus associated with ??positive illusions?? about college-success variables.     

Decomposition can harm the accuracy of behavioural frequency reports

In survey research, the use of decomposition can lead to pronounced reporting errors as seen by overreporting and overall reporting error. A total of 87 subjects answered either decomposed or undecomposed questions concerning telephone calls made by them while at work. The questionnaire conditions varied the length of the reference period (1 week or 6 months), and the type of call (local or long‐distance). Decomposition conditions introduced either spatial or temporal cues. In all comparisons, decomposed questions increased overreporting bias relative to undecomposed questions. In addition, undecomposed questions with a 1‐week reference period led to increased overreporting bias in comparison to undecomposed/6‐month questions. Results are consistent with a category split estimation model in which smaller categories are predicted to lead to overreporting, and larger categories to underreporting. Decomposition is not recommended for gaining retrospective reports of non‐distinctive, frequent events. Copyright © 2000 John Wiley & Sons, Ltd.     

Kandidaten in psychotherapeutischer Ausbildung

In the context of the discussion about a reform of psychotherapeutic training in Germany the question arises, which factors influence the decision of psychologists and physicians for a particular training. 343 candidates in psychodynamic, behavioural or psychoanalytic training were asked about their motives for the training, their professional objectives in general and their satisfaction with their choice of training. The candidates' decision for a particular training was associated with personal attitudes and professional goals, with the given information about psychotherapeutic treatment within their studies and with their field of study. For the most part, the respondents are not satisfied with the quality and quantity of information on psychotherapeutic treatment within their studies. Candidates in analytic training are altogether more satisfied with their choice of training and do not plan to start an additional psychotherapeutic training as often as candidates in behavioral training. The consequences of these results in particular for the medical and psychological curricula (a more balanced representation of psychotherapeutic methods) are discussed.     

Rationalism,irrationalism and taylorism

From Taylorism to Fordism: A Rational Madness, by Bernard Doray, London: Free Association Books, 1988, 229 pages, hb £27.50, pb £11.95.