Brain Association Studies in 2024: A Systematic Review of Sample Sizes and Preregistrations
Jan Wacker1, Katharina Paul1, Anna Scharfenecker1
1Department of Differential Psychology and Psychological Assessment, Institute of Psychology, University of Hamburg, Hamburg, Germany.
Psychophysiology
|July 25, 2026
Summary
Most psychological studies linking brain and behavior use insufficient sample sizes and lack preregistration, potentially inflating false positive findings. Improved research practices are crucial for reliable results in psychological science.
Area of Science:
- Neuroscience
- Psychology
- Behavioral Science
Background:
- Consensus exists for large sample sizes (hundreds) to detect modest psychological-behavioral associations (rho < 0.20) with adequate statistical power.
- Numerous data preprocessing and analysis choices significantly impact results, necessitating clear preregistration protocols.
Conclusions:
- Published associations between psychological variables and brain differences may be inflated due to low sample sizes and lack of preregistration, suggesting a high rate of false positives.
- Significant reforms in research methodology are urgently needed in psychological and brain sciences.
- This review offers a framework for evaluating similar issues in other scientific fields.
