Small Effects: The Indispensable Foundation for a Cumulative Psychological Science

Area of Science:

• Psychology
• Genetics
• Scientific Publishing

Background:

• Complex psychological phenomena are influenced by numerous factors.
• Genetics research suggests individual causes typically have small effects.

Purpose of the Study:

• Critique publication culture's demand for large effects.
• Advocate for recognizing the importance and reality of small effects.
• Propose methods to advance psychological science.

Main Methods:

• Drawing on genetics research to inform psychological theory.
• Analyzing the impact of publication bias on effect size reporting.
• Suggesting methodological and cultural shifts in scientific practice.

Main Results:

• Publication culture favors inflated, unreliable large effects.
• Small effects, though often overlooked, are likely real and consequential.
• Current practices hinder the identification of actual determinants in psychology.

Conclusions:

• Small effects are theoretically and practically relevant, especially at scale.
• Adopting big data, machine learning, and preregistration can improve research.
• Shifting cultural norms to value accurate, meaningful effects is crucial for reproducible science.