Critical thinkingArticle: Borsboom, Rhemtulla, Cramer, van der Maas, Scheffer and Dolan (2016)Kinds versus continua: a review of psychometric approaches to uncover the structure of psychiatric constructsThe present paper reviews psychometric modelling approaches that can be used to investigate the question whether psychopathology constructs are discrete or continuous dimensions through application of statistical models. The question of whether mental disorders should be thought of as discrete categories or as continua represents an important issue in clinical psychology and psychiatry.The DSM-V typically adheres to a categorical model, in which discrete diagnoses are based on patterns of symptoms.But, such categorizations often involve apparently arbitrary conventions. All measurement starts with categorization, the formation of equivalence classes.Equivalence classes: sets of individuals who are exchangeable with respect to the attribute of interest.We may not succeed in finding an observational procedure that in fact yields the desired equivalence classes.We may find that individuals who have been assigned the same label are not indistinguishable with respect to the attribute of interest.Because there are now three classes rather than two, next to the relation between individuals within cases (equivalence), we may also represent systematic relations between members of different cases.One may...

Critical thinkingChapter 4 of Understanding Psychology as a science by DienesBayes and the probability of hypothesesObjective probability: a long-run relative frequency.Classic (Neyman-Pearson) statistics can tell you the long-run relative frequency of different types of errors.Classic statistics do not tell you the probability of any hypothesis being true.An alternative approach to statistics is to start with what Bayesians say are people’s natural intuitions.People want statistics to tell them the probability of their hypothesis being right.Subjective probability: the subjective degree of conviction in a hypothesis. Subjective or personal probability: the degree of conviction we have in a hypothesis.Probabilities are in the mind, not in the world.The initial problem to address in making use of subjective probabilities is how to assign a precise number to how probable you think a proposition is.The initial personal probability that you assign to any theory is up to you.Sometimes it is useful to express your personal convictions in terms of odds rather than probabilities.Odds(theory is true) = probability(theory is true)/probability(theory is false)Probability = odds/(odds +1)These numbers we get from deep inside us must obey the axioms of probability.This is the stipulation that ensures the way we change our personal probability in a theory is coherent and rational.People’s intuitions about how to change probabilities in the light of new information are notoriously bad.This is where the statistician comes in and forces us to be disciplined.There are only a few axioms, each more-or-less self-evidently reasonable.Two...

Critical thinkingArticle: Borsboom, D. and Cramer, A, O, J. (2013)Network Analysis: An Integrative Approach to the Structure of Psychopathologydoi: 10.1146/annurev-clinpsy-050212-185608 The current dominant paradigm of the disease model of psychopathology is problematic.Current handling of psychopathology data is predicated on traditional psychometric approaches that are the technical mirror of of this paradigm.In these approaches, observables (clinical symptoms) are explained by means of a small set of latent variables, just like symptoms are explained by disorders.From this psychometric perspective, symptoms are regarded as measurements of a disorder, and in accordance, symptoms are aggregated in a total score that reflects a person’s stance on that latent variable.The dominant paradigm is not merely a matter of theoretical choice, but also of methodological and pragmatic necessity.In this review, we argue that complex network approaches, which are currently being developed at the crossroads of various scientific fields, have the potential to provide a way of thinking about disorders that does justice to their complex organisation.In such approaches, disorders are conceptualized as systems of causally connected symptoms rather than as effects of a latent disorder.Using network analysis techniques, such systems can be represented, analysed, and studied in their full complexity.In addition, network modeling has the philosophical advantage of dropping the unrealistic idea that symptoms of a single disorder share a...

Critical thinkingArticle: Gigerenzer, G. & Marewski, J, N. (2015)Surrogate Science: The Idol of a Universal Method for Scientific Inferencedoi: 10.1177/0149206314547522IntroductionScientific inference should not be made mechanically.Good science requires both statistical tools and informed judgment about what model to construct, what hypotheses to test, and what tools to use.This article is about the idol of a universal method of statistical inference.In this article, we make three points:There is no universal method of scientific inference, but, rather a toolbox of useful statistical methods. In the absence of a universal method, its followers worship surrogate idols, such as significant p values.The inevitable gap between the ideal and its surrogate is bridged with delusions.These mistaken beliefs do much harm. Among others, by promoting irreproducible results.If the proclaimed ‘Bayesian revolution’ were to take place, the danger is that the idol of a universal method might survive in a new guise, proclaiming that all uncertainty can be reduced to subjective probabilities.Statistical methods are not simply applied to a discipline. They change the discipline itself, and vice versa. The null ritual The most prominent creation of a seemingly universal inference method is the null ritual:Set up a null hypothesis of ‘no mean inference’ or ‘zero correlation’. Do not specify the predictions or your own research hypothesis.Use 5% as a convention for rejecting...