Given developmental alterations discussed above in reward-related brain regions, it is not surprising that adolescents differ from their younger and older counterparts in the ways that they respond to rewarding stimuli. For example, findings in laboratory animals using the conditioned place preference (CPP) paradigm suggest that motivation for many natural rewards, including social stimuli and novelty, may be enhanced during adolescence compared to adulthood. The place conditioning procedure essentially pairs the presence of a stimulus (e.g., administration of a drug, presence of a novel object, or social partner) with a distinct chamber, while pairing the absence of the stimulus with another distinct chamber on separate trials. On the test day, animals are allowed simultaneous access to both chambers, without the training stimulus being present. More time spent on the side previously paired with the training stimulus is used as an index of preference for that stimulus (i.e., the stimulus was rewarding), with more time spent on the alternative side indexing an aversion for the stimulus (i.e., a conditioned place aversion). Using this procedure, socially reared adolescent male rats were shown
