Previously we suggested that sex differences in the FRN might be accounted for by the type of paradigm employed (Crowley, Wu, Crutcher, et al., 2009), with video game formats possibly engaging males (see Hoeft, et al., 2008) and social tasks engaging females more (Fukushima & Hiraki, 2006). Viewed against the developmental data presented here, however—with younger children showing both larger FRN responses and longer latencies—it could just as easily be argued that the larger FRNs and the longer latency for reward feedback for males reflect a maturational difference, with males lagging behind females in terms of the neural architecture supporting the FRN. As another alternative, in a basic way, the sexes differ in terms of gonadal hormones testosterone and estrogen, which have been implicated in sex differences in reward processing (Dreher et al., 2007; Hermans et al., 2010). Future work will need to account for fluctuations in gonadal hormones, and possibly pubertal timing (Marceau, Ram, Houts, Grimm, & Susman, 2011), to isolate contributing factors for FRN differences across the sexes. Finally, we observed a sex effect in our source analyses,
