Estimating the mean effect size in meta-analysis: Bias,precision, and mean squared error of different weighting methods

Although use of the standardized mean difference in meta-analysis is appealing for several reasons, there are some drawbacks. In this article, we focus on the following problem: that a precision-weighted mean of the observed effect sizes results in a biased estimate of the mean standardized mean difference. This bias is due to the fact that the weight given to an observed effect size depends on this observed effect size. In order to eliminate the bias, Hedges and Olkin (1985) proposed using the mean effect size estimate to calculate the weights. In the article, we propose a third alternative for calculating the weights: using empirical Bayes estimates of the effect sizes. In a simulation study, these three approaches are compared. The mean squared error (MSE) is used as the criterion by which to evaluate the resulting estimates of the mean effect size. For a meta-analytic dataset with a small number of studies, theMSE is usually smallest when the ordinary procedure is used, whereas for a moderate or large number of studies, the procedures yielding the best results are the empirical Bayes procedure and the procedure of Hedges and Olkin, respectively.     

The human element in car following models

This commentary distinguishes between the engineering-inspired formalisms used by Brackstone, M., and McDonald, M. (Transportation Research Part F (1999)) and the psychological knowledge of, and assumptions about human behaviour when car following. It outlines a preliminary mathematical model, based on psychological knowledge about car following behaviour by human drivers, which could be applied in traffic engineering, as a means of bringing these two ways of studying car following closer together.     

How Long Do Offenders Escape Arrest? Using DNA Traces to Analyse when Serial Offenders Are Caught

Why is it that some serial offenders are arrested quickly and others only after a long period, or never at all? What characterises offenders who continue to escape arrest despite their continued involvement in crime? To be able to answer these questions, arrested (identified) offenders must be compared with never arrested (unidentified) offenders. In this paper, data from the Dutch DNA database are used to assess which characteristics of the criminal behaviour of unidentified offenders influence the probability that they will subsequently be arrested. DNA data offer a unique opportunity to compare crime series of identified offenders with crime series of yet unidentified offenders. Using the Cox proportional hazards model, we tested whether the number of crimes committed, offence specialization, and offence seriousness affect the probability of arrest of serial offenders. Results showed that as an offender commits more crimes, the probability that he will be arrested increases and that offence specialization decreases the probability of arrest. Another conclusion drawn is that DNA traces offer unique opportunities for criminological research. We discuss the limitations of this new data source and make suggestions for future research using DNA traces and for future research that might improve the current study. Copyright © 2012 John Wiley & Sons, Ltd.     

The role of goal-directed behavior in intention attribution in children

In this study, we addressed the question of the nature of the information needed by 13-month-old infants to understand another agent's intentions. In two experiments, an experimenter was either unable or unwilling to give a toy to an infant. Importantly, an implement (a gutter in which the toy could roll down toward the infant) was used to make the experimenter's behavior as similar as possible in the two conditions. When the experimenter remained still in both conditions, infants did not behave differently according to the experimenter's intentions, suggesting that they did not infer them. By contrast, in a second experiment, where the experimenter performed an action directed toward the gutter in both conditions, the infants looked away from the experimental setting more often and longer in the unwilling condition than in the unable condition. They also looked more toward the experimenter in the unable condition than in the unwilling condition. Therefore, we conclude that an agent's intentional attitude can already be inferred by a 13-month-old provided that this intention is concretely shown through a goal-directed action.     

The moderating role of empathy in the association between parental support and adolescent aggressive and delinquent behavior

The present two‐wave longitudinal study addressed the role of affective empathy and parental support in aggressive and delinquent behavior in a sample of 323 adolescents (158 boys, 165 girls). Self‐report questionnaires were used to assess affective empathy, perceived support from parents, delinquency, and aggression. Guided by theories on children's differential susceptibility to socialization, we expected adolescents with different levels of empathy to vary in their responsiveness to parental support. In agreement with our hypothesis, empathy moderated the relation of perceived parental support with aggressive and delinquent behavior. Controlling for the effect of gender and for the stability of aggression and delinquency, higher perceived parental support was predictive of lower levels of aggression at age 15, but only for adolescents high in empathy. Remarkably, adolescents low in empathy not only appeared to benefit less from parental support, but even showed more aggression and delinquency at age 15 when they perceived their parents to be more supportive at age 14. Aggr. Behav. 38:368‐377, 2012. © 2012 Wiley Periodicals, Inc.     

Development of adolescents' peer crowd identification in relation to changes in problem behaviors

This 5-wave longitudinal study, which included 1,313 Dutch adolescents, examined the development of peer crowd identification in relation to changes in problem behaviors. Adolescents from 2 age cohorts annually reported their identification with 7 peer crowds and their levels of internalizing and externalizing problem behaviors. Univariate latent growth curve analyses revealed declines (i.e., "Hip Hoppers" and "Metal Heads") or declines followed by stabilization (i.e., "Nonconformists") in identification with nonconventional crowds and increases (i.e., "Elites" and "Brains") or declines followed by stabilization (i.e., "Normals" and "Jocks") in identification with conventional crowds. Multivariate latent growth curve analyses indicated that stronger and more persistent identifications with nonconventional crowds were generally associated with more problem behaviors throughout adolescence. In contrast, stronger and more persistent identifications with conventional crowds were generally associated with fewer problem behaviors throughout adolescence with the notable exception of Brains, who showed a mixed pattern. Though characterized by fewer externalizing problems, this group did report more anxiety problems. These findings and their implications are discussed.     

Emotional Dynamics in the Development of Early Adolescent Psychopathology: A One-Year Longitudinal Study

This study examined the role of the level and variability of happiness, anger, anxiety, and sadness in the development of adolescent-reported anxiety disorder symptoms, depressive symptoms, and aggressive behavior in 452 adolescents (250 male) followed from age 13 to 14. Level and between-day variability of emotions were assessed through adolescent report at 3-month intervals across a 1 year period. Level and variability of the four emotions contributed to changes in anxiety disorder and depressive symptoms more consistently than to changes in aggressive behavior. All four emotions were predictive of changes in internalizing problems, while anger played the most prominent role in the development of aggressive behavior. Variability of emotions contributed to changes in anxiety disorder symptoms, while heightened levels of negative emotions and diminished happiness contributed to changes in depression. Results suggested somewhat stronger effects of negative affect on aggressive behavior for females than for males. Results underscore the role of emotion dysregulation in the development of psychopathology.     

Estimation of the predictive power of the model in mixed‐effects meta‐regression: A simulation study

Several methods are available to estimate the total and residual amount of heterogeneity in meta‐analysis, leading to different alternatives when estimating the predictive power in mixed‐effects meta‐regression models using the formula proposed by Raudenbush (1994, 2009). In this paper, a simulation study was conducted to compare the performance of seven estimators of these parameters under various realistic scenarios in psychology and related fields. Our results suggest that the number of studies (k) exerts the most important influence on the accuracy of the results, and that precise estimates of the heterogeneity variances and the model predictive power can only be expected with at least 20 and 40 studies, respectively. Increases in the average within‐study sample size () also improved the results for all estimators. Some differences among the accuracy of the estimators were observed, especially under adverse (small k and ) conditions, while the results for the different methods tended to convergence for more optimal scenarios.     

Changing dominance in mixed profession groups: putting theory into practice

An extended professional identity theory is proposed to enhance interprofessional collaboration. The purpose of this study is to investigate whether comparative feedback on interprofessional interaction can decrease the degree of profession-based dominance and general dominance in mixed profession groups. This observational study comprised a randomized double-blind pretest-posttest control group design with 19 mixed profession groups (10 intervention and nine control groups, each with three dental and three dental hygiene students). All groups received reflective feedback during two consecutive two hour team development meetings. Intervention groups also received comparative feedback. Profession-based dominance concerned the sum of three observation items (conversational turn-taking, dominance and contributing ideas) with a three-point scale: ?1 = dental dominance, 0 = no dominance, +1 = dental hygiene dominance. Polychoric correlations confirmed positive associations with the latent trait and an unidimensional underlying structure. Observation items were internally consistent (α > .70). General dominance concerned the sum of absolute values of observation items with a minimum value of zero (no dominance) and the maximum value of three (strong dominance). A two-way factorial ANOVA was performed. The results revealed a significant interaction effect with regard to general dominance, F(1,17) = 6.630, p = 0.020 and large effect size (partial eta squared = 0.28). Comparative feedback on interprofessional interaction decreases general dominance in mixed profession groups.