Brain Association Studies in 2024: A Systematic Review of Sample Sizes and Preregistrations.

Overview

1. Department of Differential Psychology and Psychological Assessment, Institute of Psychology University of Hamburg Hamburg Germany

Abstract

Within the field of research aiming to link psychological variables to individual differences in brain structure and function, there is a widespread consensus that (1) samples sizes at least in the hundreds are necessary to detect the presumably modest effects of typically rho < 0.20 with sufficient statistical power and that (2) a large number of equally defensible options for data preprocessing and analysis exist that have a marked impact on the final results (i.e., an issue typically addressed via a detailed preregistration). However, among 515 relevant studies published in 2024 and identified in the current systematic review the median sample size was only 101 participants (80 in studies that presumably involved data collection rather than reanalysis of preexisting data) and only 5% featured a preregistration. Whereas 96% of the studies reported at least one significant relevant association, only 2.3% reported a significant preregistered association. This pattern suggests that many of the published associations are likely false positives and that significant changes in research practices are required. The current systematic review provides a blueprint for testing whether recent research in other fields faces similar problems.

Reproduced under the paper's license (CC BY), from the paper cited above.

Code

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The paper's code and data availability statement is in the Data section.

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Data

Datasets cited

• osf:t9843, at OSF; found in “Data Availability Statement”

Data Availability Statement

The data that support the findings of this study are openly available in Open Science Framework at https://osf.io/t9843. Code Availability: All scripts are openly available on the Open Science Framework (OSF) platform (https://osf.io/t9843).

Reproduced under the paper's license (CC BY), from the paper cited above.

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Version 2, 28 September 2026

• Publisher: n/a → Wiley

Version 1, 27 September 2026: the first record

Recorded: type, language, journal, volume, issue, pages, dates, 3 authors, 9 keywords, 4 MeSH terms, 41 references.

Cite

This paper

Wacker, J., Paul, K., & Scharfenecker, A. (2026). Brain Association Studies in 2024: A Systematic Review of Sample Sizes and Preregistrations. Psychophysiology, 63(7), e70365. https://doi.org/10.1111/psyp.70365

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