“…Although money is the most commonly reported task stimulus, multiple CI tasks using nonmonetary commodities have shown good test–retest reliability and validity. The array of stimuli includes both primary natural reinforcers such as food (Estle et al, 2007; Rasmussen et al, 2010), sexual activity (Johnson & Bruner, 2013; Lawyer & Schoepflin, 2013; Lawyer et al, 2011; 2010), alcohol and other substances of abuse (Bickel et al, 2014; Odum, 2011), and conditioned, secondary reinforcers including music CDs, books, and DVDs (Charlton & Fantino, 2008), availability of social interactions (Charlton et al, 2013), and more abstract hypothetical concepts such as various types of health and environmental outcomes (Baker, Johnson, & Bickel, 2003; Hardisty & Weber, 2009; Miller & Chapman, 2001).…”