What Pilot Studies Can (and Cannot) Do for Validity in Psychological Research

Recent debates about psychology’s credibility have renewed attention to validity threats that are often difficult to evaluate from standard research reports. We argue that pilot studies can function as methodological due diligence by improving early decisions about design, measurement, manipulation, sampling, and analysis prior to a main study. We examine four types of validity: construct, internal, external, and statistical-conclusion validity. Across these domains, we show how piloting can help researchers assess whether materials and procedures function as intended, identify potential validity threats, and provide key design parameters for planning and model choice. However, we also caution that piloting can reduce validity when treated as a consequence-free space for undocumented tinkering, or when small, noisy pilots are used to justify overconfident inferences. Drawing on recent methodological debates, we distinguish two problematic uses of piloting: fragile use and opportunistic use. We discuss how hidden selection and analytic flexibility can distort the evidential value of confirmatory tests. We, then, conclude with practical recommendations for transparent pilot reporting. Greater transparency would enable readers to evaluate how pilot evidence shaped the final design of a study and consequently, how to interpret a study’s findings.