Although this chapter promotes a lifespan perspective on processes that are comprised in executive functioning (EF), the majority of research reviewed in the following sections relies on data from adults. This adult bias is inevitable, given that EF does not fully develop until adulthood and that, in children, components of EF are not sufficiently differentiated, either behaviorally or neuroanatomically (for a review, see Fiske & Holmboe, 2019). Research that does examine EF in children is primarily concerned with characterizing developmental trajectories of EF. This research has shown that rudimentary EF begins to emerge in infancy (approximately around 5-6 months of age) and experiences a fairly rapid development in early childhood (for reviews, see Best & Miller, 2010;Fiske & Holmboe, 2019). EF then continues to mature throughout adolescence and into the mid-to late 20s, as evidenced by improvements in both EF speed and EF accuracy during this period (Delis et al., 2001). Developmental improvements in performance parallel progressively greater processing efficiency (suggested by progressively more localized brain activation during EF task performance), as well as increases in synaptogenesis, neuronal proliferation and pruning, and myelination of relevant networks (for a review, see Best & Miller, 2010).