Hierarchical clause structure as a tool for cognitive advances in early childhood

Abstract

Humans have non-verbal means for various types of mental computations, particularly those that involve concrete objects and events accessible to direct sensory experience. Unlike other species, however, (adult) humans are also capable of reasoning about abstract or psychologically distant (i.e., beyond one's direct sensory access) concepts and events, such as hidden causes, other people's beliefs and desires, counterfactual situations, and distant past and future. While reasoning about such constructs may be possible without language, it is at best inefficient (slow, imprecise, and inconsistent).We present an argument that the development of clausal structure in children between the ages of 2–5 provides a representational tool for stage-like cognitive advancements of early childhood, previously documented in developmental research. In our view, this influence goes beyond the conceptual domain, but involves layers of syntactic hierarchy, which augment non-verbal representations and allow children to go beyond their primary, core non-linguistic (sensory-perceptual and affective), systems in reasoning about psychologically distant phenomena. We present the Gradual Emergence theory of syntax acquisition, in which the layers of sentence structure emerge in child language in a universal progression, beginning from the least complex, Small Clause, structure, progressing first to the development of transitivity, then finiteness, and finally to full clause. We review a broad swath of evidence from developmental psychology and detail our proposal that the acquisition of hierarchical syntax in the first few years of life provides the foundation for learning about the spatially, temporally and socially distant objects and events.