From persons to general principles: Methodological decisions for idiographic and nomothetic research

Research in psychology can have various foci, ranging from the psychological dynamics of single individuals to the generalization across individuals, often termed idiographics and nomothetics, respectively. However, terminological ambiguities have limited communication clarity about idiographics and nomothetics. Importantly, whether studies are suitable for idiographic and/or nomothetic inferences is not categorical but rather a matter of degree. Therefore, we propose a list of concrete, better-defined methodological aspects characterizing individual studies. Specifically, we highlight 16 different decisions researchers have to make pertaining to (1) research question, (2) research design, and (3) analyses and interpretation. These decisions are introduced with a focus on personality psychology but apply to psychological research broadly. We discuss the different decisions with an emphasis on their relation to idiographic and nomothetic inferential goals. Rather than providing specific recommendations, we emphasize the importance of aligning the methodology of a given study with the research question and theory. Overall, this overview seeks to help researchers make relevant decisions more intentionally to help them tailor their studies to their inferential goals.