https://bjorn-persson.github.io/Recent content on Björn PerssonHugo -- 0.147.2enWed, 27 May 2026 00:00:00 +0000https://bjorn-persson.github.io/papers/sex-differences-prediction-2026/Wed, 27 May 2026 00:00:00 +0000https://bjorn-persson.github.io/papers/sex-differences-prediction-2026/Multiple small sex differences across cognition, personality, and interests jointly predict sex with 80% accuracy and account for a substantial share of variance in occupational gender segregation. Published in Scientific Reports, 2026.https://bjorn-persson.github.io/thoughts/credentials/Fri, 15 May 2026 00:00:00 +0000https://bjorn-persson.github.io/thoughts/credentials/The male–female gap in higher education will widen, and the men opting out are not who you think. A short argument about generative AI, the right-tail of the male ability distribution, and the future of credential-based hiring.https://bjorn-persson.github.io/thoughts/does-it-hurt-to-ask/Wed, 13 May 2026 00:00:00 +0000https://bjorn-persson.github.io/thoughts/does-it-hurt-to-ask/On whether asking participants about trauma, depression, or suicidal thoughts is harmful. The empirical answer, across four decades of studies and tens of thousands of participants, is no — and the more interesting question is what it costs us not to ask.https://bjorn-persson.github.io/papers/multiverse-clpn-2026/Fri, 20 Feb 2026 00:00:00 +0000https://bjorn-persson.github.io/papers/multiverse-clpn-2026/This paper proposes multiverse analyses for evaluating cross-lagged panel network models and demonstrates the approach using psychological flexibility data. Published in Acta Psychologica, 2026.https://bjorn-persson.github.io/papers/teique-sf-irt-2025/Fri, 29 Aug 2025 00:00:00 +0000https://bjorn-persson.github.io/papers/teique-sf-irt-2025/Using IRT, this paper psychometrically refines the TEIQue-SF to a 12-item version in a Swedish multicenter sample of 845 healthcare and social work students. Published in BMC Psychology, 2025.https://bjorn-persson.github.io/location/Wed, 08 May 2024 00:00:00 +0000https://bjorn-persson.github.io/location/Björn Persson's mailing and office address at Karolinska Institutet.https://bjorn-persson.github.io/officehours/Wed, 08 May 2024 00:00:00 +0000https://bjorn-persson.github.io/officehours/Schedule and location for Björn Persson's office hours.https://bjorn-persson.github.io/papers/ipv-recidivism-2023/Tue, 07 Feb 2023 00:00:00 +0000https://bjorn-persson.github.io/papers/ipv-recidivism-2023/This study evaluates the predictive utility of the RNR-A for intimate partner violence recidivism in a cohort of 3,145 clients. Published in Nordic Journal of Criminology, 2023.https://bjorn-persson.github.io/papers/subjective-wellbeing-irt-2020/Wed, 22 Jan 2020 00:00:00 +0000https://bjorn-persson.github.io/papers/subjective-wellbeing-irt-2020/This paper applies item response theory to validate the PANAS, Satisfaction with Life Scale, and Harmony in Life Scale in a sample of 1,000 participants. Published in Frontiers in Psychology, 2020.https://bjorn-persson.github.io/papers/searching-machiavelli-2019/Wed, 01 May 2019 00:00:00 +0000https://bjorn-persson.github.io/papers/searching-machiavelli-2019/This paper investigates whether Machiavellianism represents a distinct construct or largely reflects psychopathy and narcissism, using multiple Machiavellianism measures and hierarchical analysis. Published in Personality Disorders, 2019.https://bjorn-persson.github.io/papers/successful-psychopathy-2019/Tue, 15 Jan 2019 00:00:00 +0000https://bjorn-persson.github.io/papers/successful-psychopathy-2019/This paper proposes a two-dimensional view of successful psychopathy emphasizing social status, and tests predictions using the triarchic model. Published in Personality and Individual Differences, 2019.https://bjorn-persson.github.io/papers/dsm-rdoc-2019/Tue, 01 Jan 2019 00:00:00 +0000https://bjorn-persson.github.io/papers/dsm-rdoc-2019/This book chapter reviews psychiatric classification from DSM-III to RDoC, and discusses the network approach as an alternative framework. Published in Personality and Brain Disorders, Springer, 2019.https://bjorn-persson.github.io/papers/swedish-dirty-dozen-irt-2018/Wed, 07 Mar 2018 00:00:00 +0000https://bjorn-persson.github.io/papers/swedish-dirty-dozen-irt-2018/This paper provides the first IRT analyses of the Swedish version of the Dark Triad Dirty Dozen scale in a sample of 570 individuals. Published in Heliyon, 2018.https://bjorn-persson.github.io/papers/sd3-irt-2017/Fri, 26 May 2017 00:00:00 +0000https://bjorn-persson.github.io/papers/sd3-irt-2017/This paper uses item response theory to test whether the three Dark Triad constructs measured by the SD3 can be modelled independently. Published in Personality and Individual Differences, 2017.https://bjorn-persson.github.io/papers/sd3-structure-2019/Thu, 06 Apr 2017 00:00:00 +0000https://bjorn-persson.github.io/papers/sd3-structure-2019/Across three independent samples (total N > 19,700), this paper examines the factor structure of the Short Dark Triad using exploratory and confirmatory factor analyses. Published in Assessment, 2019.https://bjorn-persson.github.io/papers/mind-body-dualism-2016/Sun, 22 May 2016 00:00:00 +0000https://bjorn-persson.github.io/papers/mind-body-dualism-2016/This paper investigates whether beliefs in mind-body dualism among Swedish university students are explained by their personal value priorities. Published in International Journal of Psychological Studies, 2016.https://bjorn-persson.github.io/papers/empathy-altruism-2016/Fri, 18 Mar 2016 00:00:00 +0000https://bjorn-persson.github.io/papers/empathy-altruism-2016/Two studies test the empathy-altruism hypothesis by examining how emotional and cognitive empathy relate to Schwartz's universal social values. Published in The Journal of Social Psychology, 2016.https://bjorn-persson.github.io/papers/dirty-dozen-2016/Tue, 01 Mar 2016 00:00:00 +0000https://bjorn-persson.github.io/papers/dirty-dozen-2016/Using the largest sample to date (N = 3,698), this paper examines the factor structure and item-level properties of the Dark Triad Dirty Dozen via IRT. Published in PeerJ, 2016.https://bjorn-persson.github.io/papers/dark-triad-values-2015/Sat, 17 Jan 2015 00:00:00 +0000https://bjorn-persson.github.io/papers/dark-triad-values-2015/Using cross-cultural data from Sweden and the US, this paper maps Dark Triad personality traits onto Schwartz's universal social values. Published in Personality and Individual Differences, 2015.https://bjorn-persson.github.io/data/data1/Thu, 07 Mar 2013 00:00:00 +0000https://bjorn-persson.github.io/data/data1/This dataset contains all irregular verbs in known Romance languages.https://bjorn-persson.github.io/courses/course1/Mon, 10 Mar 2003 00:00:00 +0000https://bjorn-persson.github.io/courses/course1/This graduate course presents classical results in Romance philology.https://bjorn-persson.github.io/books/book1/Wed, 01 Jan 1997 00:00:00 +0000https://bjorn-persson.github.io/books/book1/This book discusses Portugese irregular verbs in great details.https://bjorn-persson.github.io/courses/course2/Sat, 16 Jun 1990 00:00:00 +0000https://bjorn-persson.github.io/courses/course2/This undergraduate course discusses profanity in Early Irish.https://bjorn-persson.github.io/visualizations/cfa/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/cfa/Interactive visualization of confirmatory factor analysis: see how factor loadings determine the model-implied covariance matrix, and watch an optimizer converge to the best-fitting parameter values.https://bjorn-persson.github.io/visualizations/construct-validity/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/construct-validity/Interactive comparison of six frameworks for construct validity: Cronbach & Meehl's nomological network, Campbell & Fiske's MTMM matrix, Messick's unified framework, Borsboom's causal realism, Kane's argument-based approach, and network psychometrics.https://bjorn-persson.github.io/visualizations/correlation-stability/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/correlation-stability/Compare five association measures interactively, then watch how sample correlations converge to the population value as N increases — based on Schönbrodt & Perugini (2013).https://bjorn-persson.github.io/visualizations/cronbachs-alpha/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/cronbachs-alpha/Interactive visualization of how Cronbach's alpha determines the Standard Error of Measurement and true-score confidence intervals — with direct consequences for psychological assessment.https://bjorn-persson.github.io/visualizations/irt-curve/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/irt-curve/Interactive visualization of Item Response Theory: explore how item characteristic curves, discrimination, difficulty, and information functions reveal measurement precision that Classical Test Theory hides.https://bjorn-persson.github.io/visualizations/irt-precision/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/irt-precision/Interactive visualization of how Item Response Theory determines measurement precision. Unlike Classical Test Theory, IRT precision varies across the trait continuum — explore how item parameters control where a test is most informative.https://bjorn-persson.github.io/visualizations/measurement-error/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/measurement-error/Interactive demonstration of how imperfect reliability attenuates observed correlations, and what the correction for attenuation costs in sampling variance. Adjust the true correlation and the reliability of each observed variable.https://bjorn-persson.github.io/visualizations/multicollinearity/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/multicollinearity/Interactive visualization showing how increasing the correlation between two predictors collapses the data cloud, inflates standard errors, and destabilizes regression coefficients. A 2D projection illustrates the geometric intuition.https://bjorn-persson.github.io/visualizations/normal-distribution/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/normal-distribution/Interactive visualization of the normal density extended with skew and kurtosis. Adjust the four moments and read off lower-tail, upper-tail, two-tailed, central, or range probabilities — or invert from a target probability.https://bjorn-persson.github.io/visualizations/tabulated-traits/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/tabulated-traits/Comparative overview of major perspectives on personality — behavior genetics, CB5T, Five-Factor Theory, Eysenck, Cloninger, evolutionary, lexical Big Five, HEXACO, interpersonal circumplex, socioanalytic, attachment, whole-trait, social-cognitive, psychodynamic, narrative, personology, humanistic/SDT, and social-constructionist — sorted along a reductionist–holistic continuum.https://bjorn-persson.github.io/visualizations/tabulated-psychiatry/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/tabulated-psychiatry/Comparative overview of the major perspectives on psychiatric disorders — biomedical, RDoC, computational, phenomenological, evolutionary, HiTOP, network, psychodynamic, biopsychosocial, cognitive, interpersonal, social/cultural, PTMF, humanistic, and critical psychiatry — sorted along an ontological realism continuum.https://bjorn-persson.github.io/visualizations/range-restriction/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/range-restriction/See how restricting the range of a variable attenuates correlations and reduces statistical power.https://bjorn-persson.github.io/visualizations/regression/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/regression/Interactive visualization for fitting linear, quadratic, cubic, and logistic regression models. Set population parameters, generate synthetic data, and compare the fitted curve to the true population curve.https://bjorn-persson.github.io/visualizations/regression-to-the-mean/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/regression-to-the-mean/Interactive scatterplot demonstrating how extreme scorers at Time 1 tend to score closer to the mean at Time 2 whenever the test-retest correlation is less than perfect. A reliability slider controls that correlation, and you can click to highlight top and bottom performers.https://bjorn-persson.github.io/visualizations/reliability-validity/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/reliability-validity/Interactive archery-target metaphor for Classical Test Theory. Two sliders control random error (reliability) and systematic error (validity), updating both the target cluster and the observed-score distribution.https://bjorn-persson.github.io/visualizations/simpsons-paradox/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/simpsons-paradox/Interactive scatterplot demonstrating how an overall negative correlation can reverse into positive within-group correlations when data is grouped. Drag the grouping slider to watch the paradox unfold.https://bjorn-persson.github.io/visualizations/dichotomization/Mon, 01 Jan 0001 00:00:00 +0000https://bjorn-persson.github.io/visualizations/dichotomization/See how splitting a continuous variable into two groups discards information, attenuates effect sizes, and reduces statistical power.