ABSTRACT
The effort to define and measure mood and related affective phenomena has deep roots in psychological history (James, 1884, 1890/1998; Wundt, 1897/1998). For much of the past century, this effort has been guided by a nomothetic approach (Buss & Craik, 1980; Eysenck, 1954; Stern, 1900) that has yielded important insights into how people vary from one another in their characteristic ways of feeling (e.g., Bradburn, 1969; Diener & Emmons, 1984; Russell, 1978; Watson & Tellegen, 1985). A second tradition of mood theorizing—the idiographic approach—rooted in the important writings of Allport (1937), Cattell (1966), and Kluckhohn and Murray (1948) has likewise generated a wealth of scholarship on the value of studying single persons through intensive repeated observations of psychological states over time (e.g., Hooker, Nesselroade, Nesselroade, & Lerner, 1987; Lebo & Nesselroade, 1978; Wessman & Ricks, 1966; Zevon & Tellegen, 1982).
