Dienes & Perner (D&P) argue that nondeclarative
knowledge can take multiple forms. We provide empirical support
for this from two related lines of research about the development
of mathematical reasoning. We then describe how different forms
of procedural and declarative knowledge can be effectively modeled
in Anderson's ACT-R theory, contrasting this computational
approach with D&P's logical approach. The computational
approach suggests that the commonly observed developmental progression
from more implicit to more explicit knowledge can be viewed as
a consequence of accumulating and strengthening mental representations.
