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.     

On the interdependence of temporal and spatial judgments

Three experiments are reported on the tau and kappa effects, the dependence of judgments of distance upon duration (tau) and of judgments of duration upon distance (kappa). In Experiment 1, three lights in a horizontal sequence were used to define two temporal and two spatial intervals over a total duration of 160 msec. The subject was required to choose the shorter of either the two durations or the two distances. The results confirmed Collyer’s (1977) findings that the two effects are inconsistently observed across subjects when the display duration is brief. In Experiment 2, display duration was systematically manipulated from 160 to 1,500 msec. It is argued that relative temporal judgments should become easier as the total display duration is increased and that, hence, the kappa effect should become less marked. On the other hand, relative spatial judgments should become more difficult as the total duration of the display is increased, and the tau effect should become more marked. The data were in conformity with the hypothesis. In Experiment 3, data are presented for a tau experiment which fit the assumption that the effect depends upon a weighted average of distance and the expected distance which would be traversed in the given time at constant velocity.     

THE USE OF CONTINGENT-INTERRUPTED MUSIC IN THE TREATMENT OF DISRUPTIVE BUS-RIDING BEHAVIOR

The present study evaluated the efficacy of using contingent-interrupted music in treating the disruptive bus-riding behavior of an 8-year-old profoundly retarded female. Music was played during each bus ride as long as the subject was sitting appropriately, and interrupted contingent upon each response defined as disruptive bus riding, during an ABCDCDCDA design. A significant reduction in disruptive bus riding occurred with each introduction of contingent-interrupted music. The treatment procedure described in this report was easy to administer, produced rapid treatment gains, and showed virtually no regression during an 8-week follow-up period.     

Elementary school principals assess services of school psychologists nationwide

A one-page questionnaire was sent to 400 elementary school principals nationwide to assess their opinions regarding services of the school psychologist. These elementary school principals indicated that the school psychologist was found to be most helpful when providing the traditional services of psychological testing, personality and emotional assessment, consultation, and screening. Changes in school psychological services desired by the elementary school principals were more time from the school psychologist and an increase in individual and group counseling, preventive mental health, and inservice training. If elementary principal opinion is to be regarded, gross alterations to existing services of the school psychologist are not indicated by the results of this study.     

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.     

The effects of feedback with chronically institutionalized mental patients

The ability of two female and one male chronically institutionalized adult mental patients to comprehend and retain feedback on individualized problem behaviors and the effect of that feedback on changes in the occurrences of those behaviors were examined. Feedback on five problem behaviors was provided to each subject within a small therapy group setting employing a multiple baseline across subjects experimental design. Comprehension and retention tests occurred two, five, and seven days following the feedback in the small groups, while the rates of the occurrences of the problem behaviors were time-sampled throughout the subjects' waking day via use of the Time-Sample Behavioral Checklist (Paul, 1987). Results indicated that, although there were no changes in the rates of occurrence, these subjects were able to retain and understand the feedback on their problem behaviors. Implications for further investigations and for the utility of feedback with chronically institutionalized adults are discussed.     

Orientational anisotropy in the human visual system

When a target stimulus in a predesignated location is identified by a keypress response, responses are slightly faster if noise stimuli in adjacent locations are identical to the target than if they are a different stimulus assigned to the same response (a repeated-stimulus superiority effect). An exception to this result has been found in experiments that used randomly intermixed letter and digit stimuli. These experiments showed slower responding for identical noise than for nonidentical, response-compatible noise (a repeated-stimulus inferiority effect). The present study investigated these phenomena in three experiments. Experiments 1 and 2 established that both the superiority and inferiority effects can be obtained in the same experiment. They also provided evidence that the repeated-stimulus inferiority effect is a function of the intermixing of letters and digits and not of the larger target-set size that has been used for mixed lists. Experiment 3 demonstrated that, with unmixed presentation, the repeated-stimulus superiority effect is enhanced by an increase in the number of stimuli assigned to each response. The experiments are consistent with accounts that attribute the repeated-stimulus superiority effect to competition that occurs when different internal recognition responses are activated. Moreover, the experiments suggest that the repeated-stimulus inferiority effect has its basis in processes that occur subsequent to feature extraction.