There is evidence that mild increases in positive affect can improve problem solving skills (Isen 1984, 1987), such as cognitive flexibility (Isen & Daubman, 1984; Isen, Niedenthal & Cantor, 1992), verbal fluency (Phillips, MacLean, & Allen, 2002), and problem solving (Green & Noice, 1988; Isen, Daubman & Nowicki, 1987). However, even mild increases in positive affect do have some cost. Increased positive affect appears to interfere with one's orientation toward the pursuit of one's long-term goals, to increase one's distractibility (Dreisbach & Goschke, 2004), and to make one more optimistic about positive outcomes of a situation (Nygren, Isen, Taylor, & Dulin, 1996; Wright & Bower, 1992). These actions may in part reflect the reduced rationality described above.
