A growing number of behavioral scientists across a broad range of disciplines now recognize the central role of affect, mood, and emotion in human behavior in general, and in health behavior in particular (see Figure 1.1). For example, reference to these constructs is made at an increasing rate in the literatures on eating behavior and food choices (e.g., Lutter & Nestler, 2009; Macht, 2008; Moore & O’Donohue, 2008; Stroebe, Papies, & Aarts, 2008), the causes of the obesity epidemic (e.g., Kishi & Elmquist, 2005; Rolls, 2007), the addictive effects of drugs of abuse (e.g., Baker, Piper, McCarthy, Majeskie, & Fiore, 2004; Bechara, 2005; Koob, 2008; Robinson & Berridge, 2008), the initiation and cessation of cigarette smoking (e.g., Carmody, Vieten, & Astin, 2007; Schleicher, Harris, Catley, & Nazir, 2009), the antecedents and consequences of drinking alcohol (e.g., Gilman, Ramchandani, Davis, Bjork, & Hommer, 2008; King, de Wit, McNamara, & Cao, 2011; McKinney, 2010; McKinney & Coyle, 2006), the effects of sleep and the predictors of sleep disruptions (e.g., McCrae, McNamara, Rowe, Dzierzewski, Dirk, Marsiske, & Craggs, 2008; Walker, 2009), and the effects of exercise and the reasons behind physical inactivity (Ekkekakis, Parfitt, & Petruzzello, 2011; Rhodes, Fiala, & Conner, 2009; Williams, 2008).