Finally, the research by Brehmer et al. (2009) and Bellanderet al. (2011) suggests that influences of single DA-relevant genes on WM performance are more likely to be detectable in the context of training than for traditional single-assessment performance scores.This may reflect the fact that effects of uncontrolled variables (e.g.,motivation, test anxiety, test familiarity, alternative strategy use,relevant prior knowledge) are attenuated when people are closerto their performance maximum, as is often the case following training (Baltes and Kliegl, 1992; Brehmer et al., 2007). The Brehmeret al. and Bellander et al. studies were the first to address this issue and replication is thus needed. This is particularly critical as these studies involved relatively few subjects.