Dopaminergic and Prefrontal Contributions to Reward-Based Learning and Outcome Monitoring During Child Development and Aging Dorothea Ha ¨mmerer and Ben Eppinger Max Planck Institute for Human Development In many instances, children and older adults show similar difficulties in reward-based learning and outcome monitoring. These impairments are most pronounced in situations in which reward is uncertain (e.g., probabilistic reward schedules) and if outcome information is ambiguous (e.g., the relative value of outcomes has to be learned). Furthermore, whereas children show a greater sensitivity to external outcome information, older adults focus less on a rapid differentiation of rewarding outcomes. In this article, we review evidence for the idea that these phenomenologically similar impairments in learning and outcome monitoring in children and older adults can be attributed to deficits in different underlying neurophysiological mechanisms. We propose that in older adults learning impairments are the result of reduced dopaminergic projections to the ventromedial prefrontal cortex, which lead to less differentiated representations of reward value. In contrast, in children, impairments in learning can be primarily attributed to deficits in executive control, which may be due to a protracted development of the dorsal medial and lateral prefrontal cortices. We think that this framework maps well onto recent neurophys- iological models of reward processing and is plausible from a broader developmental perspective. Keywords: life span development, reinforcement learning, decision making, valence bias, dopamine Rewarding and punishing outcomes drive the acquisition of goal- directed behavior. However, in order to approach sources of reward or to avoid unpleasant outcomes, individuals have to constantly monitor and flexibly adjust their actions. Children, as well as older adults, show impairments in reward-based learning in situations in which demands on updating and monitoring of outcomes are high. These developmental differences in reward-based learning and outcome monitoring may reflect maturational changes in prefrontal areas (in the case of children) as well as age differences in the impact of projections from the midbrain dopamine system and associated stri- atal areas to the ventromedial prefrontal cortex (in the case of older adults). In this article, we review the current literature on life span developmental differences in reward-based learning and outcome monitoring. We try to integrate these findings into a neurophysiologi- cally plausible framework that captures age-specific difficulties across the life span. For the purpose of this article, we focused on the developmental periods of childhood (until about 12 years of age) and adulthood to old age. We deliberately excluded the adolescent age range that is already comparatively well documented (see Fareri, Martin, & Delgado, 2008; Somerville & Casey, 2010; Spear, 2000, for reviews). Reward-based learning and outcome monitoring involve a dy- namic interplay of reward and executive control processes. We conceptualize reward-related processes as mechanisms that allow the formation and updating of value representations (Grabenhorst & Rolls, 2011; Rangel, Camerer, & Montague, 2008). We think of executive control in terms of processes involved in the monitoring of actions and outcomes (see Botvinick, Braver, Barch, Carter, & Cohen, 2001; Miller & Cohen, 2001). For the purpose of this article, we primarily focused on reward-based learning as a way of acquiring goal-directed behavior. Of course, goal-directed behav- ior is acquired and represented in multiple ways, including more explicit mechanisms such as the encoding of episodic information by medial temporal lobe and lateral prefrontal structures (Polyn & Kahana, 2008; Simons & Spiers, 2003). The salience of reward information as well as the ability to monitor and control behavior changes across the life span (cf. Mohr, Li, & Heekeren, 2010). Whereas children seem to react more strongly to reward information and may be less focused on self-control, older adults seem to value rewarding cues less and focus more on the control of rewarded actions (Crone, Jennings, & Van der Molen, 2004; Eppinger, Kray, Mock, & Mecklinger, 2008; Eppinger, Mock, & Kray, 2009; Ha ¨mmerer, Li, Mu ¨ller, & Lindenberger, 2011; Mell et al., 2009; Paxton, Barch, Racine, & Braver, 2008). These changes in the relative impact of reward valuation and executive control across the life span may be due to maturational changes in the prefrontal cortex as well as age dif- ferences in the function of neuromodulatory systems (such as the midbrain dopamine system) and their projections to striatal and prefrontal areas (Ba ¨ckman, Lindenberger, Li, & Nyberg, 2010; Ba ¨ckman, Nyberg, Lindenberger, Li, & Farde, 2006; Bunge, Dudukovic, Thomason, Vaidya, & Gabrieli, 2002; Casey, Totten- ham, Liston, & Durston, 2005; Craik & Bialystok, 2006; Samanez- Larkin, Kuhnen, Yoo, & Knutson, 2010; Volkow et al., 2000). In this article, we propose that in many instances children and older adults show similar performance impairments in reward- This article was published Online First March 5, 2012. Dorothea Ha ¨mmerer and Ben Eppinger, Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany. Correspondence concerning this article should be addressed to Dorothea Ha ¨mmerer, Center for Lifespan Psychology, Max Planck Institute for Human Development, Lentzeallee 94, Berlin 14195, Germany. E-mail: haemmerer@mpib-berlin.mpg.de Developmental Psychology © 2012 American Psychological Association 2012, Vol. 48, No. 3, 862– 874 0012-1649/12/$12.00 DOI: 10.1037/a0027342 862