Using the arguable assumption that 50 kHz USVs reflect positive affect, the Willey et al. (2009) data provide evidence for reduced positive affect to social stimuli during adolescence relative to adulthood, perhaps leading the adolescents to a compensatory increase in “consumption” of this natural reward (i.e. increased social interactions) in order to achieve the desired amount of hedonic pleasure. Yet, the sucrose intake and taste reactivity data discussed above conversely provide evidence in support of an increased positive hedonic impact of palatable solutions during adolescence, with this increased hedonic pleasure perhaps precipitating increased reward consumption for its pleasurable aspects during this developmental transition. Thus, the data to date do not lead to a simple conclusion as to whether adolescence is a period of enhanced or attenuated hedonic responses to natural rewarding stimuli, nor to clear predictions regarding age-related alterations in sensitivities to drug-related rewards as well. Clearly, more research is needed to resolve these issues, with perhaps particular attention directed toward need state, as well as modality and relative intensity of reward. Indeed, when using fMRI to compare NAc activation
