In a first step, two words forming an utterance are serialized. The utterance may have a topic-comment structure. The order can be ‘topic - comment’ (), or it can be ‘comment - topic’ ().

In both cases, main stress is on the comment. The first variant will later develop into the syntactic construction [subject predicate]. In similar fashion, other syntactic constructions are learnt, like instantiating the construction [adjective noun].

After the two-word phase, the child starts forming simple sentences. Only then does he also start using morphological forms. This allows sentences like , with a conjugated verb form.

However, such forms are not yet produced by applying morphological operations; they are stored as vocables. From an age of three years on, children form such simple constructions that appear to obey rules of syntax. These constructions, however, are still handled holistically (Klein et al. 2023). Wernicke's area together with long-term memory suffices to handle utterances. It is only at four years of age that Broca's area gets involved. This is also when the child acquires grammatical marking in general. This includes formatives like articles, auxiliaries, prepositions and conjunctions.

When rules are learnt, they are often overgeneralized. For instance, the regular past tense formation may be applied to an irregular verb, producing forms like maked. Sometimes such a falsely regular form ousts the correct irregular form that had already been learnt. The irregular form had been learnt earlier because it was accessed holistically and learnt as a vocable. It is ousted by the regular form because only the rule as such has been learnt but not the fact that it does not apply to certain verbs. Only in an additional learning step is the irregular form reactivated.

Expansion of grammar is fostered considerably once the child can and does read and write. Then rarer morphological forms () and complex syntactic constructions () become available.