The Psychological Reality of the Learned 'P < .05' Boundary

The 0.05 boundary within Null Hypothesis Statistical Testing (NHST) &quot;has made a lot of people very angry and been widely regarded as a bad move&quot; (to quote Douglas Adams). Here, we move past meta-scientific arguments and ask an empirical question: What is the psychological standing of the 0.05 boundary for statistical significance? We find that graduate students in the psychological sciences show a &quot;boundary effect&quot; when relating p-values across 0.05. We propose this psychological boundary is learned through statistical training in NHST and reading a scientific literature replete with &quot;statistical significance&quot;. Consistent with this proposal, undergraduates do not show the same sensitivity to the 0.05 boundary. Additionally, the size of a graduate student&#39;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.