Within-person variability

Abstract From its emergence at the beginning of the 20th century, personality scientists pursued two goals—a nomothetic approach that investigated the structure of individual differences between people in a population and an idiographic approach that explored variation within a person relative to him or herself. In this chapter, we first track the how the history of these two perspectives impacted the study of within-person variability. Next, we review findings and unanswered contemporary questions regarding within-person variability. Finally, we conclude by providing questions for future research, some of which were proposed by early personality theorists but progressed slowly due to a lack of adequate methods. We outline cutting-edge statistical models and idiographic techniques to move the study of within-person variability—and personality science—forward.