The article discusses the reliability paradox in cognitive psychology, where robust cognitive tasks, despite their effectiveness in experimental settings, fail to produce reliable individual differences. The authors argue that the low between-subject variability that makes these tasks robust in experimental contexts also hinders their reliability for correlational studies. They conducted three studies to assess the test-retest reliability of seven classic cognitive tasks: Eriksen Flanker, Stroop, stop-signal, go/no-go, Posner cueing, Navon, and Spatial-Numerical Association of Response Code (SNARC). The results showed that the reliabilities of these tasks were surprisingly low, ranging from 0 to 0.82, primarily due to low variance between individuals rather than high measurement error. This finding suggests that well-established experimental paradigms may not directly translate to the study of individual differences in brain structure, chemistry, and function, and alternative metrics may be needed. The implications of these findings are significant for cognitive neuroscience and clinical research, as they highlight the need for researchers to consider reliability when translating experimental effects to correlational studies.The article discusses the reliability paradox in cognitive psychology, where robust cognitive tasks, despite their effectiveness in experimental settings, fail to produce reliable individual differences. The authors argue that the low between-subject variability that makes these tasks robust in experimental contexts also hinders their reliability for correlational studies. They conducted three studies to assess the test-retest reliability of seven classic cognitive tasks: Eriksen Flanker, Stroop, stop-signal, go/no-go, Posner cueing, Navon, and Spatial-Numerical Association of Response Code (SNARC). The results showed that the reliabilities of these tasks were surprisingly low, ranging from 0 to 0.82, primarily due to low variance between individuals rather than high measurement error. This finding suggests that well-established experimental paradigms may not directly translate to the study of individual differences in brain structure, chemistry, and function, and alternative metrics may be needed. The implications of these findings are significant for cognitive neuroscience and clinical research, as they highlight the need for researchers to consider reliability when translating experimental effects to correlational studies.