Although useful for revealing general rewarding and aversive properties of meaningful stimuli, CPP has been argued to reflect multiple components of reward, such as affective attribution, goal-directed behavior, and learning processes (Berridge & Robinson, 2003). Thus, age differences in CPP findings could reflect any of a composite of reward-related processes. Hence, in our work we have begun to focus on more discrete aspects of reward processes across ontogeny to better characterize motivational differences between adolescents and adults. One such strategy is to focus on assessing ontogenetic differences in the presumed hedonic affect of naturally rewarding stimuli (assuming, of course, that hedonic affect represents a valid construct in non-human mammalian species). Among the traditional methods for indexing hedonic state in studies in laboratory animals is examination of sucrose consumption, given that intake of a palatable solution is attenuated under a variety of anhedonic states in rodents (e.g. Papp & Moryl, 1996; Willner et al., 1987). When this method was used to determine possible age differences in sucrose intake between adolescent and adult rats, adolescents were found to exhibit greater sucrose consumption on a ml/kg basis relative to their adult counterparts (Wilmouth & Spear, 2009).
