We used a delay of gratification procedure that has been shown previously to predict problem behaviors in high school children (Wulfert et al. 2002). This test is quick, places a minimum burden upon the subjects, is ecologically valid, and models real-world choice situations. It also has the advantage of being a naturalistic reward choice test whereby the respondents directly experience the consequences of their choices (i.e. obtain a real rather than a hypothetical reward and experience a real rather than a hypothetical delay), which ensures active motivational engagement by the participant. Although previous studies have established a good correspondence between the discounting of real and hypothetical rewards (Johnson and Bickel 2002; Madden et al. 2003), other studies found systematic differences in the rate of discounting depending on the reward type (Hinvest and Anderson 2010). Furthermore, the use of real rewards is more suitable for research with children because they require minimum abstraction on the part of the child participant (Reynolds 2006).
