Rule and order Acquiring ordinals in Dutch and English

Using novel comparative acquisition data (from a total of 250 children aged 2;08–6;04), this first book on ordinal learning presents an acquisition pattern that is unlike any other. At first sight, the data seem straightforward: both learners of Dutch and English acquire irregular ordinal numerals (such as Dutch derde ‘third’ or English second) after regular ones (such as vierde ‘fourth’ and seventh), and even after analytic ordinal forms (hoofdstuk vijf ‘chapter five’). This holds for both comprehension and production.
What makes this process crucially different from familiar patterns in numerical and morphological development, is that there is no evidence for an initial lexical learning stage. Children acquire the first cardinals (one, two, three, four) sequentially before they can count productively. In morphological development, productive rules usually follow storage of individual forms. In the ordinal case, however, children start out with a rule (informally: cardinal + suffix = ordinal, or for analytic forms: cardinal after a noun = ordinal). Though exceptions are acquired lexically, they come in after overgeneralization errors, rather than before; ordinal acquisition is not u-shaped.
The main claim is that children use morphosyntactic structure to acquire ordinal meaning. By combining insights from linguistics, developmental psychology and numerical cognition, this work not only provides an account for how linguistic rules can be the driving force behind ordinal acquisition, but also for why ordinals are so different in the first place. Put simply, not all rule-learning is equal, in part because not all storage is equal.