Ashkanasy & Humphrey (2011b, p. 215) point out that “Level 1 is best understood in terms of affective events theory” and distinguish between positive and negative mood effects (Ashton-James & Ashkanasy 2005). In this regard, Isen (1987) stressed the role of positive affect as a catalyst of creativity and cognitive flexibility. In other words, Level 1 incorporates within-person neurophysiological processes that consist in turn of the physiological manifestations of emotion that make up cognitive functioning. Furthermore, affective reactions at this level are in large part beyond conscious control. A further noteworthy aspect of within-person variation is that, under this perspective, empirical procedures need to take account of real-time variations in affect and behavior (Fisher 2008). Researchers, for example, can use daily diary data (e.g., see Weiss et al. 1999) or experiential sampling methods (ESM; see Larson & Csikszentmihalyi 1983), where measurements are taken in real time several times over a day.