Virginia, V. (2024). Variability in Production is the Rule, Not the Exception, at the Onset of Multi-Word Speech, Language Learning and Development, 20 (1), 76-78.

Abstract

The first stage of combinatorial speech is better described as variable than
uniform. Talk of variants obscures two different aspects of language (knowledge and use) and two different aspects of language development – acquisition of the grammar (competence) and deployment of the grammar in
speaking and listening (performance). Null subjects and Determiners are
examples in English of early variability. The limited data in other languages
make it impossible to make sweeping claims about early acquisition.