A fast numerical algorithm for the estimation of diffusion model parameters

In this paper, we describe a new algorithmic approach for parameter estimation in Ratcliff's [(1978). A theory of memory retrieval. Psychological Review, 85 (2), 59-108] diffusion model. This problem, especially if inter-trial variabilities of parameters are included in the model, is computationally very expensive; the parameter estimation procedure often takes a long time even with today's high-speed computers. The algorithm described here makes the calculation of the cumulative distribution functions for predicted process durations computationally much less expensive. This improvement is achieved by solving the Kolmogorov backward equation numerically instead of employing the previously used closed form solution. Additionally, the algorithm can determine the optimum fit for one of the model parameters (the starting point z) directly, thereby reducing the dimension of the parameter search space by one. The resulting method is shown to be notably faster than the standard (closed-form solution) method for parameter estimation.     

Langzeitwirkungen psychoanalytischer und verhaltenstherapeutischer Langzeitpsychotherapien

The prospective study compares 31 patients in long-term behavior therapy with 31 patients in psychoanalytically oriented long-term therapy. A naturalistic design was applied within the German health system. All patients underwent a diagnostic interview (SCID) by an external interviewer. Only patients who fulfilled the DSM III-R criteria for a depression or an anxiety disorder were included in the study. Although the diagnoses of the patients undergoing long-term behaviour therapy and long-term psychoanalytical psychotherapy were comparable, we found that they differed in various ways. The differences arose in a number of characteristics, such as education, access to psychotherapy (recommended by professionals versus patients introducing themselves), usage of psychotropic medication, and the strain of symptoms. The average duration of long-term behavior therapy was 2.4 years and 64 sessions. The average duration of psychoanalytically oriented long-term therapy was 3.6 years and 209 sessions. Symptoms (SCL-90-R) and interpersonal problems (IIP) were examined at the beginning, after 1 year, 2.5 years, 3.5 years and after 7 years. Both groups showed significant degrees of improvement within the first 3.5 years and remained stabilized in the following 3.5 years regarding the symptomatic aspects. Focussing on the interpersonal problems, group PA showed further improvement after the 3.5-year period. The BT group however, showed no further improvement after 3.5 years but stabilized. The evaluated phase-model of psychotherapeutic change for short-term therapy was confirmed more clearly for long-term therapies of psychoanalytical orientation than for long-term therapies of behavioral orientation.     

Adolescents’ Exposure to a Sexualized Media Environment and Their Notions of Women as Sex Objects

This study was designed to investigate whether adolescents’ exposure to a sexualized media environment is associated with stronger beliefs that women are sex objects. More specifically, we studied whether the association between notions of women as sex objects and exposure to sexual content of varied explicitness (i.e., sexually non-explicit, semi-explicit, or explicit) and in different formats (i.e., visual and audio-visual) can be better described as cumulative or as hierarchical. Further, we investigated whether this association was contingent on gender. Based on data from an on-line survey of 745 Dutch adolescents aged 13 to 18, we found that the relationship between exposure to a sexualized media environment and notions of women as sex objects followed a hierarchical pattern: Starting with adolescents’ exposure to sexually semi-explicit content, the statistical significance of the relationship with notions of women as sex objects moved from semi-explicit to explicit sexual content and from visual to audio-visual formats. Exposure to sexually explicit material in on-line movies was the only exposure measure significantly related to beliefs that women are sex objects in the final regression model, in which exposure to other forms of sexual content was controlled. The relationship between exposure to a sexualized media environment and notions of women as sex objects did not differ for girls and boys.     

Sexism, Hostility toward Women, and Endorsement of Beauty Ideals and Practices: Are Beauty Ideals Associated with Oppressive Beliefs?

Relationships between the endorsement of Western beauty ideals and practices and measures of hostility toward women and sexism were studied in 159 college men and 194 college women. The participants were predominately 18 or 19 years of age and of European American ethnicity. Correlations were computed between five factor analytically derived measures of beauty ideals and practices, two measures of the thin body ideal, and the following measures: Hostility toward Women Scale (HTWS; Lonsway & Fitzgerald, 1995), Attitudes toward Women Scale (AWS; Spence & Helmreich, 1978), and the two subscales of the Ambivalent Sexism Inventory (ASI; Glick & Fiske, 1996): hostile sexism (ASI-H) and benevolent sexism (ASI-B). It was found that endorsement of Western beauty ideals and practices was associated with hostility toward women, traditional sexism, hostile sexism, and, to a lesser extent, benevolent sexism. Results support feminist critiques of beauty practices as oppressive.     

Evaluating dynamic performance: the influence of salient Gestalt characteristics on performance ratings

It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and inverted U-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed.     

Implicit memory influences the allocation of attention in visual cortex

The visual environment is highly regular, with particular objects frequently appearing in specific locations. Previous studies of visual search have shown that people take advantage of such regularities, detecting targets more quickly when they appear at a predictable location within a given spatial configuration. Moreover, this effect depends on implicit rather than explicit memory for the configurations. These studies have suggested that implicit long-term memory for contextual information influences the allocation of attention, modulating the flow of information through visual cortex. The present study used event-related potentials to provide the first direct support for this proposal. We suggest that this guidance of attention by implicit memory is important in the natural environment because it allows environmental regularities to influence perception without the intervention of limited-capacity conscious processes.     

Long-term consequences of early experience on adult avoidance learning in female rats: role of the dopaminergic system

Following our hypothesis that juvenile emotional and/or cognitive experience should affect learning performance at preweaning age as well as adulthood, the present study in female Wistar rats aimed to examine the impact of (i) avoidance training at preweaning age, (ii) exposure to repeated maternal separation, (iii) the combination of both, and (iv) the blockade of dopaminergic neurotransmission on adult two-way active avoidance learning in rats. We found that preweaning, i.e. three week old, rats were less capable of avoidance learning compared to adults. Our main findings revealed that preweaning avoidance training alone improved avoidance learning in adulthood. Furthermore, maternal separation alone also improved avoidance learning in preweaning and in adult rats, but this effect of maternal separation did not add up to the beneficial effect of preweaning avoidance training on adult learning. In addition, the pharmacological blockade of dopamine receptors during preweaning avoidance training via systemic application of haloperidol impaired preweaning avoidance performance in a dose-dependent manner. Testing the haloperidol-treated preweaning presumed "non-learners" as adults revealed that they still showed improved learning as adults. Taken together, our results strongly support the hypothesis that emotional as well as cognitive experience at preweaning age leaves an enduring "memory trace," which can facilitate learning in adulthood. Our pharmaco-behavioral studies suggest that unlike the adult brain, preweaning learning and memory formation is less dependent on dopaminergic mechanisms, which raises the intriguing question of possible alternative pathways.     

Computer-mediated communication and interpersonal attraction: an experimental test of two explanatory hypotheses.

The aims of this study were (a) to investigate the influence of computer-mediated communication (CMC) on interpersonal attraction and (b) to examine two underlying processes in the CMC-interpersonal attraction relationship. We identified two variables that may mediate the influence of CMC on interpersonal attraction: self-disclosure and direct questioning. Focusing on these potential mediating variables, we tested two explanatory hypotheses: the CMC-induced direct questioning hypothesis and the CMC-induced self-disclosure hypothesis. Eighty-one cross-sex dyads were randomly assigned to one of three experimental conditions: text-only CMC, visual CMC, and face-to-face communication. We did not find a direct effect of CMC on interpersonal attraction. However, we did find two positive indirect effects of text-only CMC on interpersonal attraction: text-only CMC stimulated both self-disclosure and direct questioning, both of which in turn enhanced interpersonal attraction. Results are discussed in light of uncertainty reduction theory and CMC theories.     

Fast-dm: A free program for efficient diffusion model analysis

In the present article, a flexible and fast computer program, called fast-dm, for diffusion model data analysis is introduced. Fast-dm is free software that can be downloaded from the authors' websites. The program allows estimating all parameters of Ratcliff's (1978) diffusion model from the empirical response time distributions of any binary classification task. Fast-dm is easy to use: it reads input data from simple text files, while program settings are specified by commands in a control file. With fast-dm, complex models can be fitted, where some parameters may vary between experimental conditions, while other parameters are constrained to be equal across conditions. Detailed directions for use of fast-dm are presented, as well as results from three short simulation studies exemplifying the utility of fast-dm.