Dr. Raphael Hartmann

Biography

Illusory Truth Effect

The illusory truth effect is a psychological phenomenon where repeated exposure to a statement makes people more likely to accept it as true, regardless of its accuracy. It occurs because repetition alone can subtly shape judgments, causing individuals to perceive repeated claims as more credible simply because they have encountered them multiple times. This effect contributes significantly to the spread and acceptance of misinformation, propaganda, and advertising.

Response Time Modeling

In cognitive psychology response time modeling involves analyzing how quickly individuals respond to stimuli or make decisions to understand underlying cognitive processes. By measuring response times, researchers can infer details about mental operations such as perception, attention, memory retrieval, and decision-making. Mathematical models, such as evidence accumulation models, use response time data to quantify how evidence accumulates and information is processed in the brain, providing insights into the speed and efficiency of cognitive functions.

Multinomial Processing Tree Models

Multinomial processing tree (MPT) models are cognitive modeling tools used to break down observable behaviors into separate, underlying cognitive processes. These models assume that cognitive tasks can be represented as a sequence of discrete processing steps, each with an associated probability. By fitting experimental data to these probabilities, MPT models help psychologists disentangle different mental processes, such as memory retrieval, guessing, or response biases, revealing insights into how distinct cognitive components contribute to overall behavior.

in press

• Pollak, K.M., Lerche, V., Hartmann, R., & Kiesel, A. (in press). Testing the convergent validity of the non-decision time parameter of the diffusion model. Journal of Experimental Psychology: Learning, Memory, and Cognition.

2025

• Wilson, L., Hartmann, R., Klauer, K. C., Laukenmann, R., & Calanchini, J. (2025). A Tutorial on Response-Time Extended Multinomial Processing Tree Models in Social Cognition. Social Cognition, 43(5), 425–451. https://doi.org/10.1521/soco.2025.43.5.425
• Hartmann, R., Koger, A., Straub, E. R., Johannsen, L., Koch, I., Stephan, D. N., Müller, H., & Kiesel, A. (2025). forceplate: An R package for processing raw force-plate time-series data. Behavior Research Methods, 57. https://doi.org/10.3758/s13428-025-02657-8

2024

• Klauer, K. C., Hartmann, R., & Meyer-Grant, C. G. (2024). RT-MPTs: Process models for response-time distributions with diffusion-model kernels. Journal of Mathematical Psychology, 120, 102857. https://doi.org/10.1016/j.jmp.2024.102857

2023

• Henrich, F., Hartmann, R., Pratz, V., Voss, A., & Klauer, K. C. (2023). The Seven-parameter Diffusion Model: an Implementation in Stan for Bayesian Analyses. Behavior Research Methods. https://doi.org/10.3758/s13428-023-02179-1
• Kloft, M., Hartmann, R., Voss,  Andreas, & Heck, D. W. (2023). The Dirichlet Dual Response Model: An Item Response Model for Continuous Bounded Interval Responses. Psychometrika. https://doi.org/10.1007/s11336-023-09924-7

2022

• Hartmann, R., Meyer-Grant, C. G., & Klauer, K. C. (2022). An adaptive rejection sampler for sampling from the Wiener diffusion model. Behavior Research Methods. Advance online publication. https://doi.org/10.3758/s13428-022-01870-z

2021

• Hartmann, R., & Klauer, K. C. (2021). Partial derivatives for the first-passage time distribution in Wiener diffusion models. Journal of Mathematical Psychology, 103, 102550. https://doi.org/10.1016/j.jmp.2021.102550

2020

• Hartmann, R., Johannsen, L., & Klauer, K. C. (2020). rtmpt: An R package for fitting response-time extended multinomial processing tree models. Behavior Research Methods, 52(3), 1313–1338. https://doi.org/doi:10.3758/s13428-019-01318-x
• Hartmann, R., & Klauer, K. C. (2020). Extending RT-MPTs to enable equal process times. Journal of Mathematical Psychology, 96, 102340. https://doi.org/10.1016/j.jmp.2020.102340

• Hartmann, A., Kulbe, L., Aktepe, S. C., & Heck, D. W. (2025). Incorporating Response Times Into Multinomial Processing Tree Models of the Illusory Truth Effect: A Comparison of RT-MPT Models [Conference presentation]. 24th Conference of the European Society for Cognitive Psychology. Sheffield, UK.
• Hartmann, R. Meyer-Grant, C. G., & Klauer, K. C. (2023, July). Partial derivatives and an adaptive rejection sampler for the Wiener diffusion model [Conference presentation]. MathPsych/ICCM/EMPG 2023. Amsterdam, the Netherlands.
• Hartmann, R. , Klauer, K. C., & Johannsen, L. (2019, August). Response time extended multinomial processing trees in R [Conference presentation]. 50th Meeting of the European Mathematical Psychology Group (EMPG), Heidelberg, Germany.
• Hartmann, R., Klauer, K. C., & Johannsen, L. (2019, June). Response time extended multinomial processing tree (RT-MPT) models in R [Conference presentation]. 34th IOPS/SMiP Summer Conference, Utrecht, the Netherlands.
• Hartmann, R. (2018, March). Recovering Rasch model parameters when the true latent traits are not normally distributed: Comparison of Bayesian and likelihood-based approaches [Poster presentation]. 60. Tagung experimentell arbeitender Psychologen, Marburg, Germany.

• Society for Mathematical Psychology

  Trainee Member of the Society for Mathematical Psychology

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• Statistical Modeling in Psychology

  Alumnus of the DFG Research Training Group “Statistical Modeling in Psychology” (SMiP)

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• Psychometrika

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• Frontiers in Bioengineering

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