 Assuming that theories can be held tacitly, perceptual learning might plausibly play a role in making observation theory laden. Raftopoulos and Zeimbekis, for instance, ask us to imagine a scientist who has undergone perceptual learning in her expert domain (2015: 19). Specifically, through repeated exposure to items in her expert domain, she has developed perceptual sensitivity to certain features, in accordance with her professional needs. This includes learned attention to particular dimensions, and involves physical changes early in her visual system (p. 19). As a result, the scientist might quite literally see the world differently within her expert domain than someone from outside her expertise would see it.