Dynamical systems modeling of the child--mother dyad: Causality between child-directed language complexity and language development


We model the causal links between child language (CL) and child-directed language (CDL). We take pairs of sequences of linguistic measurements from a longitudinal study. Each child-mother pair of sequences is considered as an instance of the trajectory of a high-dimensional dynamical system. We then use Multispatial Convergent Cross Mapping to ascertain the directions of causality between the pairs of sequences, that is, whether the complexity of CL drives that of CDL, the complexity of CDL drives that of CL, both, or neither. We find that children are responsive to the amount of speech and the diversity of words produced by their mothers, but not vice-versa. However, the syntactic diversities of the children's utterances drive the syntactic diversity of the mothers' utterances. This is evidence for fine-grained fine-tuning of CDL in response only to the syntax of CL.

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