# The psychological reality of the learned “p < .05” boundary

## TL;DR

This study shows that graduate students in psychology treat the p < .05 threshold as a psychological boundary, likely due to their training and exposure to scientific literature.

## Contribution

The study empirically demonstrates that the .05 significance boundary is psychologically learned through statistical training and scientific reading.

## Key findings

- Graduate students show a boundary effect when interpreting p-values across .05.
- Undergraduates do not exhibit the same sensitivity to the .05 boundary.
- The boundary effect in graduate students is not linked to their endorsement of questionable research practices.

## Abstract

The .05 boundary within Null Hypothesis Statistical Testing (NHST) “has made a lot of people very angry and been widely regarded as a bad move” (to quote Douglas Adams). Here, we move past meta-scientific arguments and ask an empirical question: What is the psychological standing of the .05 boundary for statistical significance? We find that graduate students in the psychological sciences show a boundary effect when relating p-values across .05. We propose this psychological boundary is learned through statistical training in NHST and reading a scientific literature replete with “statistical significance”. Consistent with this proposal, undergraduates do not show the same sensitivity to the .05 boundary. Additionally, the size of a graduate student’s boundary effect is not associated with their explicit endorsement of questionable research practices. These findings suggest that training creates distortions in initial processing of p-values, but these might be dampened through scientific processes operating over longer timescales.

The online version contains supplementary material available at 10.1186/s41235-024-00553-x.