A cluster analysis of text message users based on their demand for text messaging: A behavioral economic approach

The goal of this study was to determine whether cluster analysis could be used to identify distinct subgroups of text message users based on behavioral economic indices of demand for text messaging. Cluster analysis is an analytic technique that attempts to categorize cases based on similarities across selected variables. Participants completed a questionnaire about mobile phone usage and a hypothetical texting demand task in which they indicated their likelihood of paying an extra charge to continue to send text messages. A hierarchical cluster analysis was conducted on behavioral economic indices, such as demand intensity, demand elasticity, breakpoint, and the maximum expenditure. With the cluster analysis, we identified 3 subgroups of text message users. The groups were characterized by (a) high intensity and low elasticity, (b) high intensity and medium elasticity, and (c) low intensity and high elasticity. In a demonstration of convergent validity, there were statistically significant and conceptually meaningful differences across the subgroups in various measures of mobile phone use and text messaging. Cluster analysis is a useful tool for identifying and profiling distinct, practically meaningful groups based on behavioral indices and could provide a framework for targeting interventions more efficiently.     

Identification of everyday objects on the basis of fragmented outline versions

Although Attneave (1954 Psychological Review 61 183 193) and Biederman (1987 Psychological Review 94 115-147) have argued that curved contour segments are most important in shape perception, Kennedy and Domander (1985 Perception 14 367-370) showed that fragmented object contours are better identifiable when straight segments are shown. We used the set of line drawings published by Snodgrass and Vanderwart (1980 Journal of Experimental Psychology: Human Learning and Memory 6 174-215), to make outline versions that could be used to investigate this issue with a larger and more heterogeneous stimulus set. Fragments were placed either around the 'salient' points or around the midpoints (points midway between two salient points), creating curved versus relatively straight fragments when the original outline was fragmented (experiment 1), or angular and straight fragments when straight-line versions were fragmented (experiment 2). We manipulated fragment length in each experiment except the last one, in which we presented only selected points (experiment 3). While fragmented versions were on average more identifiable when straight fragments were shown, certain objects were more identifiable when the curved segments or the angles were shown. A tentative explanation of these results is presented in terms of an advantage for straight segments during grouping processes for outlines with high part salience, and an advantage for curved segments during matching processes for outlines with low part salience.     

Effector-related sequence learning in a bimanual-bisequential serial reaction time task

In a bimanual-bisequential version of the serial reaction time (SRT) task participants performed two uncorrelated key-press sequences simultaneously, one with fingers of the left hand and the other with fingers of the right hand. Participants responded to location-based imperative stimuli. When two such stimuli appeared in each trial, the results suggest independent learning of the two sequences and the occurrence of intermanual transfer. Following extended practice in Experiment 2, transfer of acquired sequence knowledge was not complete. Also in Experiment 2, when only one stimulus appeared in each trial specifying the responses for both hands so that there was no basis for separate stimulus-stimulus or separate response-effect learning, independent sequence learning was again evident, but there was no intermanual transfer at all. These findings suggest the existence of two mechanisms of sequence learning, one hand-related stimulus-based and the other motor-based, with only the former allowing for intermanual transfer.     

Psychotherapie und die Anerkennung des Fremden Kommentar zu D. Orlinsky

Die Arbeit setzt sich drei Ziele: Sie will Grenzen und Einschränkungen aufzeigen, die im aktuell gebräuchlichen Störungsbegriff enthalten sind. Sie will zeigen, was verloren geht, wenn die Person des einzelnen Kranken, verstanden als Individualität, Subjektivität und Identität, in Diagnostik und Therapie zu wenig beachtet wird, und sie will darauf hinweisen, dass soziale, kulturelle und gesellschaftliche Faktoren in der Psychiatrie und Psychotherapie zu berücksichtigen sind. Methodisch bedient sich die Arbeit v. a. wissenschaftstheoretischer und philosophischer Argumente. Sie kommt zur Schlussfolgerung, dass die Grenzen von Diagnostik und Therapie in allen drei Bereichen eine gemeinsame Grundlage haben. Sie lassen sich überwinden, wenn Psychiatrie und Psychotherapie selbstreflexiv die Grenzen der eigenen Verfahren berücksichtigen und wenn Fremdheit und Andersheit (des Symptoms, des Mitmenschen, des kulturellen und gesellschaftlichen Umfelds) prinzipiell anerkannt werden. Der Text versteht sich als Kommentar zu D. Orlinskys Ausführungen zur störungsspezifischen Psychotherapie aus der Sicht des Psychotherapieforschers in diesem Heft.     

Gender Differences in the Choice of Computer Courses: Applying an Expectancy-Value Model

The choice of computer courses has a direct influence on the development of computer literacy. It is alarming, therefore, that girls seem to choose computer courses less frequently than boys. The present paper examines (a) whether these often-reported gender differences also occur at the early high school level (Study 1) and (b) how these differences can be predicted by applying an expectancy-value model to the domain of computing (Study 2). Both studies clearly show gender differences in the choice of computer courses in children between 10 and 16 years in the real-life situation of choosing courses at school. In Study 2, the suggested expectancy-value model is tested using data from 159 students and 137 parents. The model shows a good fit to the data, and the observed gender differences in the choice of computer course could be predicted by differences in the value placed on computers and the expectations of success. However, these differences could only be partly explained by differences in perceived parental attitudes, and there were only weak relationships between parental attitudes and the corresponding perceptions of the students. Educational implications of the findings and suggestions for future research are discussed.     

A diffusion model decomposition of the practice effect

When people repeatedly perform the same cognitive task, their mean response times (RTs) invariably decrease. The mathematical function that best describes this decrease has been the subject of intense debate. Here, we seek a deeper understanding of the practice effect by simultaneously taking into account the changes in accuracy and in RT distributions with practice, both for correct and error responses. To this end, we used the Ratcliff diffusion model, a successful model of two-choice RTs that decomposes the effect of practice into its constituent psychological processes. Analyses of data from a 10,000-trial lexical decision task demonstrate that practice not only affects the speed of information processing, but also response caution, response bias, and peripheral processing time. We conclude that the practice effect consists of multiple subcomponents, and that it may be hazardous to abstract the interactive combination of these subcomponents in terms of a single output measure such as mean RT for correct responses. Supplemental materials may be downloaded from http://pbr .psychonomic-journals.org/content/supplemental.     

THE MODAL ARGUMENT FOR A PRIORI JUSTIFICATION

Kant famously argued that, from experience, we can only learn how something actually is, but not that it must be so. In this paper, I defend an improved version of Kant's argument for the existence of a priori knowledge, the Modal Argument , against recent objections by Casullo and Kitcher. For the sake of the argument, I concede Casullo's claim that we may know certain counterfactuals in an empirical way and thereby gain epistemic access to some nearby, nomologically possible worlds. But I maintain that our beliefs about metaphysical necessities still cannot be justified empirically. Furthermore, I reject Casullo's deflationary thesis about the significance of such justification. Kitcher's most troublesome objection is that we can gain any modal justification whatsoever through testimony , i.e. in an experiential way. This can be countered by distinguishing between productive sources of justification, like perception, and merely reproductive sources, like testimony. Thus, some productive a priori source will always be needed somewhere. ¹     

A Hierarchical Ornstein–Uhlenbeck Model for Continuous Repeated Measurement Data

In this paper, we present a diffusion model for the analysis of continuous-time change in multivariate longitudinal data. The central idea is to model the data from a single person with an Ornstein–Uhlenbeck diffusion process. We extend it hierarchically by allowing the parameters of the diffusion process to vary randomly over different persons. With this approach, both intra and interindividual differences are analyzed simultaneously. Furthermore, the individual difference parameters can be regressed on covariates, thereby providing an explanation of between-person differences. Unstructured and unbalanced data pose no problem for the model to be applied. We demonstrate the method on data from an experience sampling study to investigate changes in the core affect. It can be concluded that different factors from the five factor model of personality are related to features of the trajectories in the core affect space, such as the cross-correlation and variability of the changes.     

International Union of History and Philosophy of Science Division of Logic,Methodology and Philosophy of Science (IUHPS/DLMPS)

International Union of History and Philosophy of Science Division of Logic, Methodology and Philosophy of Science (IUHPS/DLMPS)Bulletin no. 16