Self and Identity Development in Adolescence: Neural Evidence and Implications for a Value-Based Choice Perspective on Motivated Behavior

Following a key developmental task of childhood, namely building a foundation of self-knowledge in the form of domain-specific self-concepts, adolescents begin to explore their emerging identities in ways that foster both autonomy and connectedness. Neuroimaging studies of self-related processes demonstrate enhanced engagement of ventromedial prefrontal cortex (vmPFC) in adolescence, which may both facilitate and reflect identity development by integrating across multiple sources of value. Drawing from neuroeconomic and social cognitive accounts, we propose that motivated behavior during adolescence can be modeled by a general value-based decision-making process centered around value accumulation in vmPFC. This approach advances models of adolescent neurodevelopment that focus on reward sensitivity and cognitive control by considering more diverse value inputs, including contributions of developing selfand identity-related processes. It also considers adolescent decision-making and behavior from their point of view, rather than primarily taking adults’ perspectives on what adolescents should value or how they should behave. Value-Based Decision-Making in Adolescence 3 It is well known that adolescents are physically, cognitively, and socioemotionally more advanced than children – but are still prone to behave in ways that are inconsistent with adult values and norms. Adolescents are frequently caricaturized as excessive risk-takers, overly self-focused, and highly susceptible to social pressure. Despite general agreement that such a portrayal is an oversimplification, the field is still searching for agreement on an overarching framework to explain why these tendencies are more common in adolescents than either children or adults. One influential approach, the dual-systems model (1), conceptualizes behavior in terms of a competition or conflict between orthogonal developing neural circuits implicated in reward sensitivity and cognitive control, and has made significant headway in describing how functioning of these networks may relate to adolescent risk-taking. Another prominent approach considers contributions of social information processing networks, particularly in an effort to understand the adolescent ‘social reorientation’ that broadens social influences beyond the family to feature an emphasis on peers (2). However, these models collectively do not account for the contributions of identityand selfrelated processes, such as core personal values and self-verification, to motivated adolescent behavior. This is a disconcerting gap, as the self represents a key point of intersection between social, cognitive, affective, motivational, and regulatory processes (3). To address such a gap in the field, we propose adopting a neurobiologicallygrounded model of value-based decision-making that can more flexibly accommodate more diverse inputs to behavior, such as selfand identity-related considerations, that are particularly relevant during adolescence and can alternately promote or prevent Value-Based Decision-Making in Adolescence 4 risky behavior depending on the context. We first review adolescent self and identity development, linking the behavioral and neural levels. We then outline the general value-based decision-making approach and describe the predictions of this model in the context of adolescent development. Our goal is to produce a more flexible, comprehensive account of adolescent behavior, particularly to the extent that such a model may reveal additional leverage points for translational approaches to improve adolescent outcomes, as well as enhance our understanding of positive and prosocial development in adolescence. Adolescent Self and Identity Development The adolescent period is believed to be crucial for many aspects of self and identity development including commitments, personal goals, motivations, and associated psychosocial well-being (4-7). An enhanced priority for autonomy, particularly from parents, develops concurrently with increased relational identity commitments and needs for connectedness with peers (8). Relatedly, self-evaluations become increasingly differentiated and complex across roles and relationships (9). Adolescents also frequently self-report high levels of self-consciousness, and more generally exhibit greater concern with and interest in others’ perceptions of the self (10). Given the theoretical and empirical prominence of changes in aspects of self and identity during adolescence, a growing body of research has begun to examine how this may be expressed at a neural level. Most of this work has examined self-evaluation, typically by asking participants to engage in explicit reflection on the selfdescriptiveness of various (often overtly positive or negative) traits and attributes. Like Value-Based Decision-Making in Adolescence 5 adults, children and early adolescents engage cortical and subcortical midline structures, in particular vmPFC and adjacent rostral/perigenual anterior cingulate cortex (ACC), more during self-evaluations than when evaluating another social target (10-12; although this pattern can be attenuated with very close others like adolescents’ best friends, 13, 14). Even in varied clinical populations of children and adolescents, there is usually activation of vmPFC during self-evaluations relative to most control conditions. Typically-developing youth also seem to engage vmPFC more during self-evaluations in comparison to those with autism spectrum disorder (3), and perhaps those experiencing depression (15, 16). We are just beginning to learn more about how neural responses elicited by selfevaluation develop across adolescence, rather than between childhood or adolescence and adulthood. Two cross-sectional studies focusing on the self-reference effect in memory (wherein information evaluated in relation to the self is remembered better than other information), revealed some relatively continuous developmental trajectories for neural correlates of self-evaluation. The studies found that rostral/perigenual ACC activity increased across ages 7-13 during encoding for self versus mother (17), and increased across ages 13-19 during encoding for self versus distant other (18). Furthermore, in a longitudinal fMRI study examining children at age 10 and again at age 13, stable responses across timepoints were observed in rostral/perigenual ACC (and VS) during self-evaluations (19). There were also increases over time during evaluations of self (relative to other) in vmPFC, which were most pronounced for selfevaluations made in the social (compared to academic) domain, and adolescents who reported more advancement through pubertal development exhibited the greatest Value-Based Decision-Making in Adolescence 6 increases in vmPFC during social self-evaluations. This suggests the interrelated biological and social changes associated with puberty may impact self-referential processes, and potentially the value derived from them. Although vmPFC and adjacent rostral/perigenual ACC is emphasized in these studies eliciting self-evaluative processes, several other regions of interest appear in these studies. As mentioned above, VS responses have been observed not only during direct self-evaluations (19), but also indirect (“reflected”) social self-evaluations, specifically thinking about what a best friend thinks of your social abilities (14). The involvement of VS during self-evaluation is consistent with the adult literature, which highlights the overlap between self-reference and reward (20) through the assignment of value (21). Additionally, dorsal mPFC (dmPFC) and TPJ are sometimes more active in child and adolescent self-evaluations (10, 11, 18), whereas in adults these regions are typically attuned to mentalizing, social perspective-taking, and evaluations of others. Notably, in adults, functional connectivity between TPJ and vmPFC is positively related to generosity (22), suggesting that TPJ might affect social value by modulating the vmPFC during choices involving the self and others. In summary, the functional neuroimaging literature demonstrates that explicit self-evaluative processes as well as more indirect forms of social self-evaluation implicated in relational identity robustly engage vmPFC and rostral/perigenual ACC (as part of a broader network including VS, TPJ, and dmPFC) in children and adolescents, often moreso than in adults. Early evidence from several studies suggests activity in vmPFC and rostral/perigenual ACC appears to increase from late childhood through middle adolescence, at which point it may either plateau or continue to increase. These Value-Based Decision-Making in Adolescence 7 findings are consistent with empirical evidence and theoretical proposals that the adolescent period is critical for identity development (4-7). Despite the behavioral and neural evidence of the elevated importance of selfand identity-related processes during adolescence, what role these processes may play in neurodevelopmental models of adolescent behavior is unclear. Dual-systems models in particular focus on a mismatch between mature reward-related circuitry and immature cognitive control circuitry (1). However, self/identity does not fit clearly in either category, including because it can alternately or concurrently contribute to rewardseeking and regulatory behavior. For example, a teen with an emerging academic identity is likely to prioritize studying over other activities, though it is unclear whether the effect of such an identity operates through rewarding or regulatory processes (or both, or this distinction may not even be theoretically meaningful for self/identity). In the next section, we present a model that gives selfand identity-related processes a prominent role in determining behavior and provides an explanation for one prominent functional role of the vmPFC during this period. Value-Based Decision-Making as a Mechanism of Motivated Beha