Who stands out? Defining, measuring, and uncovering the elements of unusualness

Perhaps surprisingly, personality science has not yet adequately addressed a very basic aspect of individuality: The extent to which an individual differs from others, a phenomenon we refer to as unusualness. In this work, we provide a framework for defining, measuring, and uncovering the elements of unusualness. First, we define unusualness as the extent to which an individual’s personality deviates from that of others in the population, either through rare expression of individual variables (unusual values) or through atypical co-occurrence of multiple variables (unusual combinations), and distinguish it from related concepts in personality research. Second, we introduce and compare various methods to measure unusualness in a simulation study and demonstrate how reliability and validity of unusualness measures can be established. Third, we propose methods to uncover the elements of unusualness (i.e., unusual values, unusual combinations) and validate these methods through simulation. Fourth, we illustrate our framework using three empirical datasets (combined N = 1,834) and multiple assessment methods, showing that unusualness can be reliably measured and offering first insights into its generalizability, nomological network, incremental validity, and possible explanatory factors. Finally, we outline conceptual, methodological, and empirical directions for future research on unusualness.