Dept. Social Psychology

Dr. Johannes Ziegler

2025-Postdoctoral researcher, Ulm University, Institute of Psychology and Education, Department of Social Psychology
2022-2025Postdoctoral researcher, Ludwig Maximilians Universität München, Department Psychology, Chair of Social Psychology
2016-2022PhD student, Heidelberg University, Psychology Institute, Chair of Social Psychology
2020Visiting PhD Student, Universitat Pompeu Fabra, Department of Economics and Business, Barcelona

Contact

Dr. Johannes Ziegler (née Prager) 
Postdoctoral Researcher

✉ johannes.ziegler(at)uni-ulm.de
☎ +49-(0)731/50 31163
Π 47.2.281

Consultation hours
on appointment

Research Interests

  • Information sampling in judgement and decision making
    • Inter‑personal and group impression formation and updating
    • Estimation, updating, and mental scaling
    • Antecedents and consequences of optional stopping in information acquisition
    • Diagnosticity of information
    • Adaptation in speed‑accuracy trade‑offs
  • Replicability, Open Science, meta-science
    • Determinants and constraints of replicability of research results
    • Theory development and diagnostic hypothesis testing
    • Validity of design and measures in original and replication research
       

Publications

  • Gollwitzer, M., & Ziegler, J. (in press). Overspecification – An overlooked but essential aspect of psychological theory development. Zeitschrift für Psychologie.
  • Ziegler, J., & Fiedler, K. (2025). Small sample size and group homogeneity: a crucial ingredient to inter-group bias. Personality and Social Psychology Bulletin, 51(9), 1631-1647. https://doi.org/10.1177/01461672231223335  
  • McCaughey, L., Ziegler, J., & Fiedler, K. (2025). Rivals reloaded: Adapting to sample-based speed–accuracy trade-offs through competitive pressure. Journal of Experimental Psychology: Learning, Memory, and Cognition, 51(7), 1034–1047. https://doi.org/10.1037/xlm0001408
  • Gollwitzer, M., & Prager, J. (2024). Getting lost in an infinite design space is no solution. Behavioral and Brain Sciences, 47, e44. https://doi.org/10.1017/S0140525X23002236
  • Fiedler, K., Prager, J., & McCaughey, L. (2023). Metacognitive myopia: A major obstacle on the way to rationality. Current Directions in Psychological Science, 32(1), 49-56. https://doi.org/10.1177/09637214221126906
  • Gollwitzer, M., Prager, J., Altenmüller, M. S., & Zein, R. A. (2023). Simplification is Not Indoctrination. Psychology Learning & Teaching, 22(3), 245-250. https://doi.org/10.1177/14757257231195352  
  • Fiedler, K., Salmen, K., & Prager, J. (2022). Toward stronger tests of rationality claims: Spotlight on the rule of succession. Decision, 9(3), 195–211. https://doi.org/10.1037/dec0000167
  • Prager, J., & Fiedler, K. (2021). Forming impressions from self-truncated samples of traits – Interplay of Thurstonian and Brunswikian sampling effects. Journal of Personality and Social Psychology, 121(3), 474–497. https://doi.org/10.1037/pspa0000274
  • Fiedler, K., McCaughey, L., & Prager, J. (2021). Quo vadis, methodology? The key role of manipulation checks for validity control and quality of science. Perspectives on Psychological Science, 16(4), 816–826. https://doi.org/10.1177/1745691620970602
  • Fiedler, K., McCaughey, L., Prager, J., Eichberger, J., & Schnell, K. (2021). Speed-accuracy trade-offs in sample-based decisions. Journal of Experimental Psychology: General, 150(6), 1203–1224. https://doi.org/10.1037/xge0000986
  • Prager, J., Krueger, J. I., & Fiedler, K. (2018). Towards a deeper understanding of impression formation – New insights gained from a cognitive-ecological perspective. Journal of Personality and Social Psychology, 115(3), 379–397. https://doi.org/10.1037/pspa0000123
  • Fiedler, K., & Prager, J. (2018). The regression trap and other pitfalls of replication science – Illustrated by the report of the Open Science Collaboration. Basic and Applied Social Psychology, 40(3), 115–124. https://doi.org/10.1080/01973533.2017.1421953