Publications by authors named "Irene Klugkist"

36 Publications

A review of applications of the Bayes factor in psychological research.

Psychol Methods 2022 Mar 17. Epub 2022 Mar 17.

Department of Methodology and Statistics.

The last 25 years have shown a steady increase in attention for the Bayes factor as a tool for hypothesis evaluation and model selection. The present review highlights the potential of the Bayes factor in psychological research. We discuss six types of applications: Bayesian evaluation of point null, interval, and informative hypotheses, Bayesian evidence synthesis, Bayesian variable selection and model averaging, and Bayesian evaluation of cognitive models. We elaborate what each application entails, give illustrative examples, and provide an overview of key references and software with links to other applications. The article is concluded with a discussion of the opportunities and pitfalls of Bayes factor applications and a sketch of corresponding future research lines. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
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http://dx.doi.org/10.1037/met0000454DOI Listing
March 2022

A randomized controlled dismantling study of Visual Schema Displacement Therapy (VSDT) vs an abbreviated EMDR protocol vs a non-active control condition in individuals with disturbing memories.

Eur J Psychotraumatol 2021 Apr 9;12(1):1883924. Epub 2021 Apr 9.

Research Department, PSYTREC, Bilthoven, The Netherlands.

: Visual Schema Displacement Therapy (VSDT) is a novel therapy for the treatment of fears and trauma-related mental health problems including PTSD. VSDT proved to be effective in reducing emotionality of aversive memories in healthy individuals in two previous randomized controlled trials and outperformed both a non-active control condition (CC) and an abbreviated version of EMDR therapy, a well-established first-line treatment for posttraumatic stress disorder. : In an effort to enhance the understanding concerning the efficacy of VSDT, and to determine its active components, a dismantling study was conducted in individuals with disturbing memories in which the effects of VSDT were tested against EMDR therapy, a non-active CC and three different VSDT-protocols, each excluding or altering a hypothesized active component. : Participants ( = 144) were asked to recall an emotional aversive event and were randomly assigned to one of these six interventions, each lasting 8 minutes. Emotional disturbance and vividness of participants' memories were rated before and after the intervention and at one and four-week follow-up. : Replicatory Bayesian analyses supported hypotheses in which VSDT was superior to the CC and the EMDR condition in reducing emotionality, both directly after the intervention and at one week follow-up. However, at four-week follow-up, VSDT proved equal to EMDR while both treatments were superior to the CC. Concerning vividness the data also showed support for hypotheses predicting VSDT being equal to EMDR and both being superior to the CC in vividness reduction. Further analyses specifying differences between the abbreviated VSDT protocols detected no differences between these conditions. : It remains unclear how VSDT yields its positive effects. Because VSDT appears to be unique and effective in decreasing emotionality of aversive memories, replication of the results in clinical samples is needed.
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http://dx.doi.org/10.1080/20008198.2021.1883924DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8043526PMC
April 2021

Expert opinion as priors for random effects in Bayesian prediction models: Subclinical ketosis in dairy cows as an example.

PLoS One 2021 14;16(1):e0244752. Epub 2021 Jan 14.

Division Farm Animal Health, Department of Population Health Sciences, Utrecht University, TD Utrecht, The Netherlands.

Random effects regression models are routinely used for clustered data in etiological and intervention research. However, in prediction models, the random effects are either neglected or conventionally substituted with zero for new clusters after model development. In this study, we applied a Bayesian prediction modelling method to the subclinical ketosis data previously collected by Van der Drift et al. (2012). Using a dataset of 118 randomly selected Dutch dairy farms participating in a regular milk recording system, the authors proposed a prediction model with milk measures as well as available test-day information as predictors for the diagnosis of subclinical ketosis in dairy cows. While their original model included random effects to correct for the clustering, the random effect term was removed for their final prediction model. With the Bayesian prediction modelling approach, we first used non-informative priors for the random effects for model development as well as for prediction. This approach was evaluated by comparing it to the original frequentist model. In addition, herd level expert opinion was elicited from a bovine health specialist using three different scales of precision and incorporated in the prediction as informative priors for the random effects, resulting in three more Bayesian prediction models. Results showed that the Bayesian approach could naturally take the clustering structure of clusters into account by keeping the random effects in the prediction model. Expert opinion could be explicitly combined with individual level data for prediction. However in this dataset, when elicited expert opinion was incorporated, little improvement was seen at the individual level as well as at the herd level. When the prediction models were applied to the 118 herds, at the individual cow level, with the original frequentist approach we obtained a sensitivity of 82.4% and a specificity of 83.8% at the optimal cutoff, while with the three Bayesian models with elicited expert opinion, we obtained sensitivities ranged from 78.7% to 84.6% and specificities ranged from 75.0% to 83.6%. At the herd level, 30 out of 118 within herd prevalences were correctly predicted by the original frequentist approach, and 31 to 44 herds were correctly predicted by the three Bayesian models with elicited expert opinion. Further investigation in expert opinion and distributional assumption for the random effects was carried out and discussed.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0244752PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808599PMC
May 2021

Basic Motor Skills of Children With Down Syndrome: Creating a Motor Growth Curve.

Pediatr Phys Ther 2020 10;32(4):375-380

's Heeren Loo (Drs P. Lauteslager and T. Lauteslager and Ms Van den Heuvel), Ermelo, the Netherlands; Department of Pedagogical and Educational Sciences: Cognitive and Motor Disabilities (Dr Volman), Utrecht University, Utrecht, the Netherlands; 's Heeren Loo, the Netherlands (Dr T. Lauteslager); Department of Pedagogical and Educational Sciences (Dr Jongerling), Erasmus School of Social and Behavioural Sciences, Rotterdam, the Netherlands; Department Methodology and Statistics (Dr Klugkist), Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, the Netherlands.

Purpose: To create a motor growth curve based on the Test of Basic Motor Skills for Children with Down Syndrome (BMS) and estimate the age of achieving BMS milestones.

Methods: A multilevel exponential model was applied to create a motor growth curve based on BMS data from 119 children with Down syndrome (DS) aged 2 months to 5 years. Logistic regression was applied to estimate the 50% probability of achieving BMS milestones.

Results: The BMS growth curve had the largest increase during infancy with smaller increases as children approached the predicted maximum score. The age at which children with DS have a 50% probability of achieving the milestone sitting was 22 months, for crawling 25 months, and for walking 38 months.

Conclusions: The creation of a BMS growth curve provides a standardization of the gross motor development of children with DS. Physical therapists then may monitor a child's individual progress and improve clinical decisions.
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http://dx.doi.org/10.1097/PEP.0000000000000743DOI Listing
October 2020

Quantitizing findings from qualitative studies for integration in mixed methods reviewing.

Res Synth Methods 2020 May 15;11(3):413-425. Epub 2020 Mar 15.

Department of Methodology and Statistics, Faculty of Social and Behavioral Sciences, Utrecht University, Tilburg, Netherlands.

In mixed methods reviewing, data from quantitative and qualitative studies are combined at the review level. One possible way to combine findings of quantitative and qualitative studies is to quantitize qualitative findings prior to their incorporation in a quantitative review. There are only a few examples of the quantification of qualitative findings within this context. This study adds to current research on mixed methods review methodology by reporting the pilot implementation of a new four-step quantitizing approach. We report how we extract and quantitize the strength of relationships found in qualitative studies by assigning correlations to vague quantifiers in text fragments. This article describes (a) how the analysis is prepared; (b) how vague quantifiers in text fragments are organized and transformed to numerical values; (c) how qualitative studies as a whole are assigned effect sizes; and (d) how the overall mean effects size and variance can be calculated. The pilot implementation shows how findings from 26 primary qualitative studies are transformed into mean effect sizes and corresponding variances.
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http://dx.doi.org/10.1002/jrsm.1403DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317911PMC
May 2020

Discussion points for Bayesian inference.

Nat Hum Behav 2020 06;4(6):561-563

Faculty of Behavioural and Social Sciences, University of Groningen, Groningen, The Netherlands.

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http://dx.doi.org/10.1038/s41562-019-0807-zDOI Listing
June 2020

A step-by-step guide on preregistration and effective data sharing for psychopathology research.

J Abnorm Psychol 2019 Aug;128(6):517-527

Department of Clinical Psychology, Utrecht University.

Data analysis in psychopathology research typically entails multiple stages of data preprocessing (e.g., coding of physiological measures), statistical decisions (e.g., inclusion of covariates), and reporting (e.g., selecting which variables best answer the research questions). The complexity and lack of transparency of these procedures have resulted in two troubling trends: the central hypotheses and analytical approaches are often selected after observing the data, and the research data are often not properly indexed. These practices are particularly problematic for (experimental) psychopathology research because the data are often hard to gather due to the target populations (e.g., individuals with mental disorders), and because the standard methodological approaches are challenging and time consuming (e.g., longitudinal studies). Here, we present a workflow that covers study preregistration, data anonymization, and the easy sharing of data and experimental material with the rest of the research community. This workflow is tailored to both original studies and secondary statistical analyses of archival data sets. In order to facilitate the implementation of the described workflow, we have developed a free and open-source software program. We argue that this workflow will result in more transparent and easily shareable psychopathology research, eventually increasing and replicability reproducibility in our research field. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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http://dx.doi.org/10.1037/abn0000424DOI Listing
August 2019

Circular Modelling of Circumplex Measurements for Interpersonal Behavior.

Assessment 2021 03 1;28(2):585-600. Epub 2019 Jul 1.

Utrecht University, Utrecht, Netherlands.

This article describes a new way to analyze data from the interpersonal circumplex (IPC) for interpersonal behavior. Instead of analyzing Agency and Communion separately or analyzing the IPC's octants, we propose using a circular regression model that allows us to investigate effects on a blend of Agency and Communion. The proposed circular model is called a projected normal (PN) model. We illustrate the use of a PN mixed-effects model on three repeated measures data sets with circumplex measurements from interpersonal and educational psychology. This model allows us to detect different types of patterns in the data and provides a more valid analysis of circumplex data. In addition to being able to investigate the effect on the location (mean) of scores on the IPC, we can also investigate effects on the spread (variance) of scores on the IPC. We also introduce new tools that help interpret the fixed and random effects of PN models.
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http://dx.doi.org/10.1177/1073191119858407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7883006PMC
March 2021

Adjustment for unmeasured confounding through informative priors for the confounder-outcome relation.

BMC Med Res Methodol 2018 12 22;18(1):174. Epub 2018 Dec 22.

Department of Methodology and Statistics, Faculty of Social and Behavioral Sciences, Utrecht University, Utrecht, The Netherlands.

Background: Observational studies of medical interventions or risk factors are potentially biased by unmeasured confounding. In this paper we propose a Bayesian approach by defining an informative prior for the confounder-outcome relation, to reduce bias due to unmeasured confounding. This approach was motivated by the phenomenon that the presence of unmeasured confounding may be reflected in observed confounder-outcome relations being unexpected in terms of direction or magnitude.

Methods: The approach was tested using simulation studies and was illustrated in an empirical example of the relation between LDL cholesterol levels and systolic blood pressure. In simulated data, a comparison of the estimated exposure-outcome relation was made between two frequentist multivariable linear regression models and three Bayesian multivariable linear regression models, which varied in the precision of the prior distributions. Simulated data contained information on a continuous exposure, a continuous outcome, and two continuous confounders (one considered measured one unmeasured), under various scenarios.

Results: In various scenarios the proposed Bayesian analysis with an correctly specified informative prior for the confounder-outcome relation substantially reduced bias due to unmeasured confounding and was less biased than the frequentist model with covariate adjustment for one of the two confounding variables. Also, in general the MSE was smaller for the Bayesian model with informative prior, compared to the other models.

Conclusions: As incorporating (informative) prior information for the confounder-outcome relation may reduce the bias due to unmeasured confounding, we consider this approach one of many possible sensitivity analyses of unmeasured confounding.
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http://dx.doi.org/10.1186/s12874-018-0634-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6303957PMC
December 2018

Effects of "Visual Schema Displacement Therapy" (VSDT), an abbreviated EMDR protocol and a control condition on emotionality and vividness of aversive memories: Two critical analogue studies.

J Behav Ther Exp Psychiatry 2019 06 27;63:48-56. Epub 2018 Nov 27.

Altrecht Academic Anxiety Centre, Altrecht GGz, Utrecht, the Netherlands; Department of Clinical Psychology, Utrecht University, Utrecht, the Netherlands.

Background And Objectives: Visual Schema Displacement Therapy (VSDT) is a novel therapy which has been described as a treatment for stress and dysfunction caused by a traumatic event. Although its developers claim this therapy is quicker and more beneficial than other forms of trauma therapy, its effectiveness has not been tested.

Methods: We compared the efficacy of VSDT to an abbreviated EMDR protocol and a non-active control condition (CC) in two studies. In Study 1 participants (N = 30) were asked to recall three negative emotional memories under three conditions: VSDT, EMDR, and a CC, each lasting 8 min. Emotional disturbance and vividness of the memories were rated before and after the (within group) conditions. The experiment was replicated using a between group study. In Study 2 participants (N = 75) were assigned to one of the three conditions, and a follow-up after 6-8 days was added.

Results: In both studies VSDT and EMDR were superior to the CC in reducing emotional disturbance, and VSDT was superior to EMDR. VSDT and EMDR outperformed the CC in terms of reducing vividness.

Limitation: Results need to be replicated in clinical samples.

Conclusions: It is unclear how VSDT yields positive effects, but irrespective of its causal mechanisms, VSDT warrants clinical exploration.
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http://dx.doi.org/10.1016/j.jbtep.2018.11.006DOI Listing
June 2019

One Direction? A Tutorial for Circular Data Analysis Using R With Examples in Cognitive Psychology.

Front Psychol 2018 30;9:2040. Epub 2018 Oct 30.

Department of Methodology and Statistics, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, Netherlands.

Circular data is data that is measured on a circle in degrees or radians. It is fundamentally different from linear data due to its periodic nature (0° = 360°). Circular data arises in a large variety of research fields. Among others in ecology, the medical sciences, personality measurement, educational science, sociology, and political science circular data is collected. The most direct examples of circular data within the social sciences arise in cognitive and experimental psychology. However, despite numerous examples of circular data being collected in different areas of cognitive and experimental psychology, the knowledge of this type of data is not well-spread and literature in which these types of data are analyzed using methods for circular data is relatively scarce. This paper therefore aims to give a tutorial in working with and analyzing circular data to researchers in cognitive psychology and the social sciences in general. It will do so by focusing on data inspection, model fit, estimation and hypothesis testing for two specific models for circular data using packages from the statistical programming language R.
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http://dx.doi.org/10.3389/fpsyg.2018.02040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6218623PMC
October 2018

Prediction models for clustered data with informative priors for the random effects: a simulation study.

BMC Med Res Methodol 2018 08 6;18(1):83. Epub 2018 Aug 6.

Department of Methodology and Statistics, Faculty of Social and Behavioral Sciences, Utrecht University, Utrecht, The Netherlands.

Background: Random effects modelling is routinely used in clustered data, but for prediction models, random effects are commonly substituted with the mean zero after model development. In this study, we proposed a novel approach of including prior knowledge through the random effects distribution and investigated to what extent this could improve the predictive performance.

Methods: Data were simulated on the basis of a random effects logistic regression model. Five prediction models were specified: a frequentist model that set the random effects to zero for all new clusters, a Bayesian model with weakly informative priors for the random effects of new clusters, Bayesian models with expert opinion incorporated into low informative, medium informative and highly informative priors for the random effects. Expert opinion at the cluster level was elicited in the form of a truncated area of the random effects distribution. The predictive performance of the five models was assessed. In addition, impact of suboptimal expert opinion that deviated from the true quantity as well as including expert opinion by means of a categorical variable in the frequentist approach were explored. The five models were further investigated in various sensitivity analyses.

Results: The Bayesian prediction model using weakly informative priors for the random effects showed similar results to the frequentist model. Bayesian prediction models using expert opinion as informative priors showed smaller Brier scores, better overall discrimination and calibration, as well as better within cluster calibration. Results also indicated that incorporation of more precise expert opinion led to better predictions. Predictive performance from the frequentist models with expert opinion incorporated as categorical variable showed similar patterns as the Bayesian models with informative priors. When suboptimal expert opinion was used as prior information, results indicated that prediction still improved in certain settings.

Conclusions: The prediction models that incorporated cluster level information showed better performance than the models that did not. The Bayesian prediction models we proposed, with cluster specific expert opinion incorporated as priors for the random effects showed better predictive ability in new data, compared to the frequentist method that replaced random effects with zero after model development.
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http://dx.doi.org/10.1186/s12874-018-0543-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6080562PMC
August 2018

Evidence Synthesis in Harm Assessment of Medicines Using the Example of Rosiglitazone and Myocardial Infarction.

Front Med (Lausanne) 2017 22;4:228. Epub 2018 Feb 22.

Department of Methodology and Statistics, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, Netherlands.

The current system of harm assessment of medicines has been criticized for relying on intuitive expert judgment. There is a call for more quantitative approaches and transparency in decision-making. Illustrated with the case of cardiovascular safety concerns for rosiglitazone, we aimed to explore a structured procedure for the collection, quality assessment, and statistical modeling of safety data from observational and randomized studies. We distinguished five stages in the synthesis process. In Stage I, the general research question, population and outcome, and general inclusion and exclusion criteria are defined and a systematic search is performed. Stage II focusses on the identification of sub-questions examined in the included studies and the classification of the studies into the different categories of sub-questions. In Stage III, the quality of the identified studies is assessed. Coding and data extraction are performed in Stage IV. Finally, meta-analyses on the study results per sub-question are performed in Stage V. A Pubmed search identified 30 randomized and 14 observational studies meeting our search criteria. From these studies, we identified 4 higher level sub-questions and 4 lower level sub-questions. We were able to categorize 29 individual treatment comparisons into one or more of the sub-question categories, and selected study duration as an important covariate. We extracted covariate, outcome, and sample size information at the treatment arm level of the studies. We extracted absolute numbers of myocardial infarctions from the randomized study, and adjusted risk estimates with 95% confidence intervals from the observational studies. Overall, few events were observed in the randomized studies that were frequently of relatively short duration. The large observational studies provided more information since these were often of longer duration. A Bayesian random effects meta-analysis on these data showed no significant increase in risk of rosiglitazone for any of the sub-questions. The proposed procedure can be of additional value for drug safety assessment because it provides a stepwise approach that guides the decision-making in increasing process transparency. The procedure allows for the inclusion of results from both randomized an observational studies, which is especially relevant for this type of research.
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http://dx.doi.org/10.3389/fmed.2017.00228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5827152PMC
February 2018

Bayesian hypothesis testing for human threat conditioning research: an introduction and the condir R package.

Eur J Psychotraumatol 2017 16;8(sup1):1314782. Epub 2017 May 16.

Department of Clinical Psychology, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, The Netherlands.

Threat conditioning procedures have allowed the experimental investigation of the pathogenesis of Post-Traumatic Stress Disorder. The findings of these procedures have also provided stable foundations for the development of relevant intervention programs (e.g. exposure therapy). Statistical inference of threat conditioning procedures is commonly based on -values and Null Hypothesis Significance Testing (NHST). Nowadays, however, there is a growing concern about this statistical approach, as many scientists point to the various limitations of -values and NHST. As an alternative, the use of Bayes factors and Bayesian hypothesis testing has been suggested. In this article, we apply this statistical approach to threat conditioning data. In order to enable the easy computation of Bayes factors for threat conditioning data we present a new R package named condir, which can be used either via the R console or via a Shiny application. This article provides both a non-technical introduction to Bayesian analysis for researchers using the threat conditioning paradigm, and the necessary tools for computing Bayes factors easily.
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http://dx.doi.org/10.1080/20008198.2017.1314782DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632775PMC
May 2017

Circular interpretation of regression coefficients.

Br J Math Stat Psychol 2018 02 4;71(1):75-95. Epub 2017 Sep 4.

Department of Methodology and Statistics, Utrecht University, The Netherlands.

The interpretation of the effect of predictors in projected normal regression models is not straight-forward. The main aim of this paper is to make this interpretation easier such that these models can be employed more readily by social scientific researchers. We introduce three new measures: the slope at the inflection point (b ), average slope (AS) and slope at mean (SAM) that help us assess the marginal effect of a predictor in a Bayesian projected normal regression model. The SAM or AS are preferably used in situations where the data for a specific predictor do not lie close to the inflection point of a circular regression curve. In this case b is an unstable and extrapolated effect. In addition, we outline how the projected normal regression model allows us to distinguish between an effect on the mean and spread of a circular outcome variable. We call these types of effects location and accuracy effects, respectively. The performance of the three new measures and of the methods to distinguish between location and accuracy effects is investigated in a simulation study. We conclude that the new measures and methods to distinguish between accuracy and location effects work well in situations with a clear location effect. In situations where the location effect is not clearly distinguishable from an accuracy effect not all measures work equally well and we recommend the use of the SAM.
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http://dx.doi.org/10.1111/bmsp.12108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811843PMC
February 2018

Reporting of Bayesian analysis in epidemiologic research should become more transparent.

J Clin Epidemiol 2017 Jun 18;86:51-58.e2. Epub 2017 Apr 18.

Department of Epidemiology, Julius Center for Health Sciences and Primary Care, UMC Utrecht, Huispost Str. 6.131, PO Box 85500, Utrecht 3508 GA, The Netherlands.

Objectives: The objective of this systematic review is to investigate the use of Bayesian data analysis in epidemiology in the past decade and particularly to evaluate the quality of research papers reporting the results of these analyses.

Study Design And Setting: Complete volumes of five major epidemiological journals in the period 2005-2015 were searched via PubMed. In addition, we performed an extensive within-manuscript search using a specialized Java application. Details of reporting on Bayesian statistics were examined in the original research papers with primary Bayesian data analyses.

Results: The number of studies in which Bayesian techniques were used for primary data analysis remains constant over the years. Though many authors presented thorough descriptions of the analyses they performed and the results they obtained, several reports presented incomplete method sections and even some incomplete result sections. Especially, information on the process of prior elicitation, specification, and evaluation was often lacking.

Conclusion: Though available guidance papers concerned with reporting of Bayesian analyses emphasize the importance of transparent prior specification, the results obtained in this systematic review show that these guidance papers are often not used. Additional efforts should be made to increase the awareness of the existence and importance of these checklists to overcome the controversy with respect to the use of Bayesian techniques. The reporting quality in epidemiological literature could be improved by updating existing guidelines on the reporting of frequentist analyses to address issues that are important for Bayesian data analyses.
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http://dx.doi.org/10.1016/j.jclinepi.2017.04.008DOI Listing
June 2017

Blurring emotional memories using eye movements: individual differences and speed of eye movements.

Eur J Psychotraumatol 2016 4;7:29476. Epub 2016 Jul 4.

Clinical Psychology, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, The Netherlands.

Background: In eye movement desensitization and reprocessing (EMDR), patients make eye movements (EM) while recalling traumatic memories. Making EM taxes working memory (WM), which leaves less resources available for imagery of the memory. This reduces memory vividness and emotionality during future recalls. WM theory predicts that individuals with small working memory capacities (WMCs) benefit more from low levels of taxing (i.e., slow EM) whereas individuals with large WMC benefit more from high levels of taxing (i.e., fast EM).

Objective: We experimentally examined and tested four prespecified hypotheses regarding the role of WMC and EM speed in reducing emotionality and vividness ratings: 1) EM-regardless of WMC and EM speed-are more effective compared to no dual task, 2) increasing EM speed only affects the decrease in memory ratings irrespective of WMC, 3) low-WMC individuals-compared to high-WMC individuals-benefit more from making either type of EM, 4) the EM intervention is most effective when-as predicted by WM theory-EM are adjusted to WMC.

Method: Undergraduates with low (n=31) or high (n=35) WMC recalled three emotional memories and rated vividness and emotionality before and after each condition (recall only, recall + slow EM, and recall + fast EM).

Results: Contrary to the theory, the data do not support the hypothesis that EM speed should be adjusted to WMC (hypothesis 4). However, the data show that a dual task in general is more effective in reducing memory ratings than no dual task (hypothesis 1), and that a more cognitively demanding dual task increases the intervention's effectiveness (hypothesis 2).

Conclusions: Although adjusting EM speed to an individual's WMC seems a straightforward clinical implication, the data do not show any indication that such a titration is helpful.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933794PMC
http://dx.doi.org/10.3402/ejpt.v7.29476DOI Listing
July 2016

Bayesian methods including nonrandomized study data increased the efficiency of postlaunch RCTs.

J Clin Epidemiol 2015 Apr 28;68(4):387-96. Epub 2014 Nov 28.

Department of Epidemiology, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Universiteitsweg 100, P.O. Box 85500, 3508 GA Utrecht, The Netherlands; Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Universiteitsweg 99, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.

Objectives: Findings from nonrandomized studies on safety or efficacy of treatment in patient subgroups may trigger postlaunch randomized clinical trials (RCTs). In the analysis of such RCTs, results from nonrandomized studies are typically ignored. This study explores the trade-off between bias and power of Bayesian RCT analysis incorporating information from nonrandomized studies.

Study Design And Setting: A simulation study was conducted to compare frequentist with Bayesian analyses using noninformative and informative priors in their ability to detect interaction effects. In simulated subgroups, the effect of a hypothetical treatment differed between subgroups (odds ratio 1.00 vs. 2.33). Simulations varied in sample size, proportions of the subgroups, and specification of the priors.

Results: As expected, the results for the informative Bayesian analyses were more biased than those from the noninformative Bayesian analysis or frequentist analysis. However, because of a reduction in posterior variance, informative Bayesian analyses were generally more powerful to detect an effect. In scenarios where the informative priors were in the opposite direction of the RCT data, type 1 error rates could be 100% and power 0%.

Conclusion: Bayesian methods incorporating data from nonrandomized studies can meaningfully increase power of interaction tests in postlaunch RCTs.
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http://dx.doi.org/10.1016/j.jclinepi.2014.11.015DOI Listing
April 2015

Behavior as information about threat in anxiety disorders: a comparison of patients with anxiety disorders and non-anxious controls.

J Behav Ther Exp Psychiatry 2014 12 11;45(4):489-95. Epub 2014 Jul 11.

Methodology and Statistics, Utrecht University, The Netherlands.

Background: Gangemi, Mancini, and van den Hout (2012) argued that anxious patients use safety behaviors as information that the situation in which the safety behaviors are displayed is dangerous, even when that situation is objectively safe. This was concluded from a vignette study in which anxious patients and non-clinical controls rated the dangerousness of scripts that were safe or dangerous and in which the protagonist did or did not display safety behaviors. Patients were more likely to take safety behavior as evidence that the situation was dangerous, especially in safe situations. Their non-clinical group may not have been psychologically naïve. We critically replicated the Gangemi et al. study using a psychologically non-informed control group.

Method: The same materials were used and patients (Obsessive Compulsive Disorder, Panic Disorder, Social Phobia; n = 30 per sub-group) were compared to matched non-patients. Using Bayesian statistics, data from the Gangemi et al. samples and the present groups were (re-)analyzed testing the hypothesis relative to non-patients, patients infer threat from safety behaviors, especially if displayed in safe situations.

Results: The Gangemi et al. data yielded a Bayes factor of 3.31 in support of the hypothesis. The present Bayes Factor was smaller (2.34), but strengthened the support for the hypothesis expressed by an updated Bayes factor of 3.31 × 2.34 = 7.75.

Conclusions: The finding that anxious patients infer threat from safety behaviors, in particular in safe contexts, was corroborated, suggesting one way in which safety behaviors are involved in the maintenance of anxiety disorders.
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http://dx.doi.org/10.1016/j.jbtep.2014.07.002DOI Listing
December 2014

Evaluating order-constrained hypotheses for circular data from a between-within subjects design.

Psychol Methods 2014 Sep 21;19(3):398-408. Epub 2014 Jul 21.

Department of Methodology and Statistics, University of Utrecht.

Researchers in psychology often encounter data measured in angles (e.g., directions, or measurements on circular scales such as the circumplex model of affect). Due to periodicity, the evaluation of these circular data requires special statistical methods. This article introduces new tests for the analysis of order-constrained hypotheses for circular data. Through these tests, researchers can evaluate their expectations regarding the outcome of an experiment directly by representing their ideas in the form of a hypothesis containing inequality constraints. The resulting data analysis is generally more powerful than one using null hypothesis testing. An example of circular data from psychology is presented to illustrate the use of the tests. Results from a simulation study show that the tests perform well in terms of type I error and power.
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http://dx.doi.org/10.1037/a0037414DOI Listing
September 2014

Properties of hypothesis testing techniques and (Bayesian) model selection for exploration-based and theory-based (order-restricted) hypotheses.

Br J Math Stat Psychol 2015 May 28;68(2):220-45. Epub 2014 Jun 28.

Department of Methodology and Statistics, Utrecht University, The Netherlands.

In this paper, the performance of six types of techniques for comparisons of means is examined. These six emerge from the distinction between the method employed (hypothesis testing, model selection using information criteria, or Bayesian model selection) and the set of hypotheses that is investigated (a classical, exploration-based set of hypotheses containing equality constraints on the means, or a theory-based limited set of hypotheses with equality and/or order restrictions). A simulation study is conducted to examine the performance of these techniques. We demonstrate that, if one has specific, a priori specified hypotheses, confirmation (i.e., investigating theory-based hypotheses) has advantages over exploration (i.e., examining all possible equality-constrained hypotheses). Furthermore, examining reasonable order-restricted hypotheses has more power to detect the true effect/non-null hypothesis than evaluating only equality restrictions. Additionally, when investigating more than one theory-based hypothesis, model selection is preferred over hypothesis testing. Because of the first two results, we further examine the techniques that are able to evaluate order restrictions in a confirmatory fashion by examining their performance when the homogeneity of variance assumption is violated. Results show that the techniques are robust to heterogeneity when the sample sizes are equal. When the sample sizes are unequal, the performance is affected by heterogeneity. The size and direction of the deviations from the baseline, where there is no heterogeneity, depend on the effect size (of the means) and on the trend in the group variances with respect to the ordering of the group sizes. Importantly, the deviations are less pronounced when the group variances and sizes exhibit the same trend (e.g., are both increasing with group number).
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http://dx.doi.org/10.1111/bmsp.12041DOI Listing
May 2015

A test of order-constrained hypotheses for circular data with applications to human movement science.

J Mot Behav 2012 13;44(5):351-63. Epub 2012 Sep 13.

Department of Methodology and Statistics, University of Utrecht, the Netherlands.

Researchers studying the movements of the human body often encounter data measured in angles (e.g., angular displacements of joints). The evaluation of these circular data requires special statistical methods. The authors introduce a new test for the analysis of order-constrained hypotheses for circular data. Through this test, researchers can evaluate their expectations regarding the outcome of an experiment directly by representing their ideas in the form of a hypothesis containing inequality constraints. The resulting data analysis is generally more powerful than one using standard null hypothesis testing. Two examples of circular data from human movement science are presented to illustrate the use of the test. Results from a simulation study show that the test performs well.
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http://dx.doi.org/10.1080/00222895.2012.709549DOI Listing
April 2013

Augmenting Data With Published Results in Bayesian Linear Regression.

Multivariate Behav Res 2012 Jun;47(3):369-91

b Utrecht University.

In most research, linear regression analyses are performed without taking into account published results (i.e., reported summary statistics) of similar previous studies. Although the prior density in Bayesian linear regression could accommodate such prior knowledge, formal models for doing so are absent from the literature. The goal of this article is therefore to develop a Bayesian model in which a linear regression analysis on current data is augmented with the reported regression coefficients (and standard errors) of previous studies. Two versions of this model are presented. The first version incorporates previous studies through the prior density and is applicable when the current and all previous studies are exchangeable. The second version models all studies in a hierarchical structure and is applicable when studies are not exchangeable. Both versions of the model are assessed using simulation studies. Performance for each in estimating the regression coefficients is consistently superior to using current data alone and is close to that of an equivalent model that uses the data from previous studies rather than reported regression coefficients. Overall the results show that augmenting data with results from previous studies is viable and yields significant improvements in the parameter estimation.
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http://dx.doi.org/10.1080/00273171.2012.673957DOI Listing
June 2012

Tones inferior to eye movements in the EMDR treatment of PTSD.

Behav Res Ther 2012 May 19;50(5):275-9. Epub 2012 Feb 19.

Clinical and Health Psychology, Utrecht University, Utrecht, The Netherlands.

Eye Movement Desensitization and Reprocessing (EMDR) is an effective treatment for posttraumatic stress disorder (PTSD). During EMDR, patients make eye movements (EMs) while recalling traumatic memories, but recently therapists have replaced EMs by alternating beep tones. There are no outcome studies on the effects of tones. In an earlier analogue study, tones were inferior to EMs in the reduction of vividness of aversive memories. In a first EMDR session, 12 PTSD patients recalled trauma memories in three conditions: recall only, recall + tones, and recall + EMs. Three competing hypotheses were tested: 1) EMs are as effective as tones and better than recall only, 2) EMs are better than tones and tones are as effective as recall only, and 3) EMs are better than tones and tones are better than recall only. The order of conditions was balanced, each condition was delivered twice, and decline in memory vividness and emotionality served as outcome measures. The data strongly support hypothesis 2 and 3 over 1: EMs outperformed tones while it remained unclear if tones add to recall only. The findings add to earlier considerations and earlier analogue findings suggesting that EMs are superior to tones and that replacing the former by the latter was premature.
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http://dx.doi.org/10.1016/j.brat.2012.02.001DOI Listing
May 2012

The activation of alternative response candidates: when do doubts kick in?

Acta Psychol (Amst) 2012 Jan 17;139(1):38-45. Epub 2011 Nov 17.

Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands.

In the current study, we investigated at which moment during visual object categorization alternative interpretations are most strongly activated. According to an early activation account, we are uncertain about how to interpret the visual information early in the categorization process. This uncertainty will vanish over time and therefore, the number of possible response candidates decreases over time. According to a late activation account, the visual information is categorized quickly, but after extensive viewing alternative interpretations become more strongly activated. Therefore, the number of possible response candidates increases over time. To increase perceptual uncertainty we used morphed figures composed of a dominant and nondominant object. The similarity rating between morphed figures and their nondominant object was taken as indicator for the activation of the nondominant response candidate: high similarity indicates that the nondominant object is relatively strongly activated as an alternative response candidate. Presentation times were varied in order to distinguish between the early and late activation account. Using a Bayesian model selection approach, we found support for the late activation account, but not for the early activation account. It thus seems that in a late stage of the categorization process the influence of the nondominant response candidate is strongest.
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http://dx.doi.org/10.1016/j.actpsy.2011.10.013DOI Listing
January 2012

The role of local and distal landmarks in the development of object location memory.

Dev Psychol 2011 Nov 26;47(6):1515-24. Epub 2011 Sep 26.

Helmholtz Research Institute, Department of Experimental Psychology, Utrecht University, Utrecht, the Netherlands.

To locate objects in the environment, animals and humans use visual and nonvisual information. We were interested in children's ability to relocate an object on the basis of self-motion and local and distal color cues for orientation. Five- to 9-year-old children were tested on an object location memory task in which, between presentation and test, the availability of local and distal cues was manipulated. Additionally, participants' viewpoint could be changed. We used a Bayesian model selection approach to compare our hypotheses. We found that, to remain oriented in space, 5-year-olds benefit from visual information in general, 7-year-olds benefit from visual cues when a viewpoint change takes place, and 9-year-olds do not benefit from the availability of visual cues for orientation but rely on self-movement cues instead. Results are discussed in terms of the adaptive combination model (Newcombe & Huttenlocher, 2006).
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http://dx.doi.org/10.1037/a0025273DOI Listing
November 2011

Incorporation of historical data in the analysis of randomized therapeutic trials.

Contemp Clin Trials 2011 Nov 25;32(6):848-55. Epub 2011 Jun 25.

Utrecht University, Department of Methodology and Statistics, Heidelberglaan 1, 3584 CS Utrecht, The Netherlands.

Historical studies provide a valuable source of information for the motivation and design of later trials. Bayesian techniques offer possibilities for the quantitative inclusion of prior knowledge within the analysis of current trial data. Combining information from previous studies into an informative prior distribution is, however, a delicate case. The power prior distribution is a tool to estimate the effect of an intervention in a current study sample, while accounting for the information provided by previous research. In this study we evaluate the use of the power prior distribution, illustrated with data from a large randomized clinical trial on the effect of ST-wave analysis in intrapartum fetal monitoring. We advocate the use of a power prior distribution with pre-specified fixed study weights based on differences in study characteristics. We propose obtaining a ranking of the historical studies via expert elicitation, based on relevance for the current study, and specify study weights accordingly.
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http://dx.doi.org/10.1016/j.cct.2011.06.002DOI Listing
November 2011

Tactile body image disturbance in anorexia nervosa.

Psychiatry Res 2011 Nov 28;190(1):115-20. Epub 2011 May 28.

Experimental Psychology, Helmholtz Research Institute, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, The Netherlands.

Body image disturbances are central to anorexia nervosa (AN). Previous studies have focused mainly on attitudinal and visual aspects. Studies on somatosensory aspects thus far have been scarce. We therefore investigated whether AN patients and controls differed in tactile perception, and how this tactile body image related to visual body image and body dissatisfaction. The Tactile Estimation Task (TET) measured tactile body image: Two tactile stimuli were applied to forearm and abdomen, and, while blindfolded, participants estimated the distance between the two tactile stimuli between their thumb and index finger. The Distance Comparison Task (DCT) measured visual body image. Compared to controls (n=25), AN patients (n=20) not only visualized their body less accurately, but also overestimated distances between tactile stimuli on both the arm and abdomen, which might reflect a disturbance in both visual and tactile body image. High levels of body dissatisfaction were related to more severe inaccuracies in the visual mental image of the body, and overestimation of tactile distances. Our results imply that body image disturbances in AN are more widespread than previously assumed as they not only affect visual mental imagery, but also extend to disturbances in somatosensory aspects of body image.
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http://dx.doi.org/10.1016/j.psychres.2011.04.031DOI Listing
November 2011

Evaluating order-constrained hypotheses for circular data using permutation tests.

Br J Math Stat Psychol 2012 May 11;65(2):222-36. Epub 2011 May 11.

Department of Methodology and Statistics, Utrecht University, The Netherlands.

Psychological researchers in different fields sometimes encounter circular or directional data. Circular data are data measured in the form of angles or two-dimensional orientations. As an example, experiments investigating the development of spatial memory and the influence of visual experience on haptic orientation perception are presented. Three permutation tests are proposed for the evaluation of ordered hypotheses. The quality of the permutation tests is investigated by means of several simulation studies. The results of these studies show the expected increase in power when the permutation tests for ordered hypotheses are compared to a common non-directional test for circular data. The differences in power between the three tests for ordered alternatives are small.
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http://dx.doi.org/10.1111/j.2044-8317.2011.02018.xDOI Listing
May 2012
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