EZ does it! Extensions of the EZ-diffusion model

In this rejoinder, we address two of Ratcliff’s main concerns with respect to the EZ-diffusion model (Ratcliff, 2008). First, we introduce “robust-EZ,” a mixture model approach to achieve robustness against the presence of response contaminants that might otherwise distort parameter estimates. Second, we discuss an extension of the EZ model that allows the estimation of starting point as an additional parameter. Together with recently developed, user-friendly software programs for fitting the full diffusion model (Vandekerckhove & Tuerlinckx, 2007; Voss & Voss, 2007), the development of the EZ model and its extensions is part of a larger effort to make diffusion model analyses accessible to a broader audience, an effort that is long overdue.     

The power to detect sex differences in IQ test scores using Multi-Group Covariance and Means Structure Analyses

Research into sex differences in general intelligence, g, has resulted in two opposite views. In the first view, a g-difference is nonexistent, while in the second view, g is associated with a male advantage. Past research using Multi-Group Covariance and Mean Structure Analysis (MG-CMSA) found no sex difference in g. This failure raised the question whether the g-difference is truly absent or whether MG-CMSA lacked statistical power to detect it. The present study used the likelihood ratio test to investigate the power to detect a g-difference in the WAIS-III factor structure with MG-CMSA. Various situations were examined including those reported in the literature. Results showed that power varies greatly among different scenarios. The scenarios based on previous results were associated with power coefficients of about 0.5–0.6. Implications of these findings are discussed in the light of research into sex differences in IQ.     

Heteroscedastic one‐factor models and marginal maximum likelihood estimation

In the present paper, a general class of heteroscedastic one‐factor models is considered. In these models, the residual variances of the observed scores are explicitly modelled as parametric functions of the one‐dimensional factor score. A marginal maximum likelihood procedure for parameter estimation is proposed under both the assumption of multivariate normality of the observed scores conditional on the single common factor score and the assumption of normality of the common factor score. A likelihood ratio test is derived, which can be used to test the usual homoscedastic one‐factor model against one of the proposed heteroscedastic models. Simulation studies are carried out to investigate the robustness and the power of this likelihood ratio test. Results show that the asymptotic properties of the test statistic hold under both small test length conditions and small sample size conditions. Results also show under what conditions the power to detect different heteroscedasticity parameter values is either small, medium, or large. Finally, for illustrative purposes, the marginal maximum likelihood estimation procedure and the likelihood ratio test are applied to real data.     

Dimensions of DSM-IV personality disorders and life-success

This study examined associations between dimensional representations of DSM-IV personality disorders and life-success in a community sample of 304 men at age 48. Measures included a standardized social interview and the SCID-II for assessment of personality disorders. The identified indicators of life-success were factor-analyzed resulting in two moderately correlated components representing "status and wealth" and "successful intimate relationships." Avoidant, obsessivecompulsive, and narcissistic dimensional scores were positively associated with "status and wealth." Inverse relationships were found between dependent, schizotypal, schizoid, and adult antisocial personality disorder dimensions and this domain of life-success. Avoidant, schizoid, and borderline personality disorder dimensions were negatively associated with "successful intimate relationships." The findings suggest that although most personality disorders are associated with impaired psychosocial functioning and life-failure, some personality disorder traits (even if considered as pathological) can contribute positively to one important aspect of life-success: status and wealth.     

Altered emotional decision-making in prisoners with borderline personality disorder

Previous studies have identified neuropsychological deficits in individuals with antisocial personality disorder and/or psychopathy. Few studies have examined neuropsychological functioning in individuals with borderline personality disorder (BPD), and no studies have yet investigated cognitive and emotional function in male prisoners with BPD. In this study, we compared the risky decision-making of 17 participants with a history of serious violent or sexual offenses and a diagnosis of DSM-IV BPD with that of 17 participants with similar offending histories but personality disorders other than BPD. Those with BPD exhibited altered processing of information about potential losses (punishment) when the probability of gains (reward) was high; they also increased their choice of risky options even in circumstances where this was clearly avoidable. These data suggest that individuals with a diagnosis of BPD and a history of serious offenses have problems integrating different reinforcement signals when choosing between risky actions, perhaps reflecting corticolimbic dysfunction as an underlying mechanism in BPD.     

Does treatment really make psychopaths worse? A review of the evidence

We aimed to evaluate critically the evidence behind the perceived inverse association between the degree of psychopathy as reflected by a high score on the Hare Psychopathy Checklist-Revised (PCL-R) and treatment response. A literature search with the key identifiers of PCL-R (or its derivatives) and treatment response produced 24 studies that were then systematically evaluated. This showed that only three studies were of an appropriate research design to answer the question and of these, none met our standard for an acceptable study. We conclude therefore that the commonly held belief of an inverse relationship between high-scores on the PCL-R and treatment response has not been established.     

Why g is not an adaptation: a comment on Kanazawa (2004)

In S. Kanazawa's evolutionary theory of general intelligence (g), g is presented as a species-typical information-processing mechanism. This conceptualization of g departs radically from the accepted conceptualization of g as a source of individual differences that is manifest in the positive manifold. Kanazawa's theory is thus problematic in the sense that it concerns a purely hypothetical, and empirically unsupported, conceptualization of g. The authors argue that an evolutionary account of g should address it as a source of individual differences--that is, in a manner that is consistent with the empirical support for g.     

The importance of an evidence-based approach in the current Spanish policy for crime prevention

This introductory paper has two objectives. On the one hand, to present the guidelines of the evidence-based perspective on crime prevention as an alternative to the usual criminal policy, which often disregards conclusions based on scientific evidence. On the other hand, to discuss the contemporary situation in Spain regarding crime prevention and particularly the role psychology develops in terms of the utility/effectiveness dichotomy. The evidence-based perspective on crime prevention is guided by the main criteria of collecting the best scientific evidence in relation to 'what works best' in the different areas of crime prevention. In that purpose systematic reviews and meta-analyses are strongly recommended. The Campbell Collaboration in Crime and Justice is a scientific endeavour oriented to prepare rigorous and systematic reviews of high-quality evidence about 'what works'. Regarding crime prevention in Spain it is argued that psychology and other disciplines must make society and its rulers see that intervention based on evidence-based policy is essential for crime prevention.     

Imaging the developing brain: what have we learned about cognitive development?

The human brain undergoes significant changes in both its structural architecture and functional organization across the life span. Advances in neuroimaging techniques over the past decade have allowed us to track these changes safely in the human in vivo. We review the imaging literature on the neurobiology of cognitive development, focusing specifically on cognitive task-dependent changes observed in brain physiology and anatomy across childhood and adolescence. The findings suggest that cortical function becomes fine-tuned with development. Brain regions associated with more basic functions such as sensory and motor processes mature first, followed by association areas involved in top-down control of behavior.