Child Language Lab
Developmental possibilities: modal variables in acquisition and change
The language development process is rich ground for theorization about language change. Each child must learn their individual grammar(s) via the indirect process of analyzing the output of others’ grammars (the input; e.g., Lightfoot, 1979), and the process necessarily involves social transmission over several years. However, while change literatures emphasize acquisition, and sociolinguists have conducted studies on the acquisition of variable input (e.g., Labov, 1989; Smith, Durham, & Richards, 2013), acquisition research on where new variants come from and why they’re directional in their incrementation (Labov 2001, 2007; advancement of the innovative variant) is rare. I present acquisition work on variable-meaning modal verbs (must, have to; (1)), testing change theory predictions, to help fill this gap and spur discussion.
(1) a. Kitty must eat catfood…
i. …because he’s on a vet-ordered diet. Root (obligation)
ii. …because he’s a cat, and that’s what cats do. Epistemic (habitual)
b. Kitty must’ve eaten his catfood…
i. #…because he’s on a diet. #Root (obligation)
ii. …because his bowl is empty. Epistemic
Modals like must or have to in diachrony first arise with root meanings ((1a-i.) e.g., obligation, teleological) and later gain epistemic ((1b-ii) e.g., inferential) interpretations. Then, the more innovative epistemic uses gradually overtake root use in a process of incrementation (e.g., Traugott 1989; Tagliamonte & D’Arcy, 2007). I discuss experimental work testing for biases in line with incrementation in preschool children (Cournane & Pérez-Leroux, in revision). We used a picture-preference task to test preferred interpretations (root vs. epistemic) for meaning-variable bare-verb constructions (1a) compared to meaning-invariant aspect-marked constructions (1b). We found that once children are at ceiling for epistemic interpretations for aspect-marked sentences, they overgenerate epistemic interpretations for the meaning-variable construction, which adults in the same community still prefer root interpretations for. We argue that the overgeneration we observed is motivated by the syntax-semantics mapping of English functional verb modals which occur overtly above aspect (in line with an epistemic interpretation; Hacquard 2010). Once children reliably work out the syntax-semantics relations for variable-meaning modals, they overgenerate the “above-aspect” interpretation to sentences without grammatical aspect (in the spirit of rule-learning overgeneration). I also discuss recent work showing an analogous pattern of “overshooting” the input in the ph-domain (Hall & Maddeaux 2018, in prep). I discuss these findings in light of children’s potential roles in language change innovation and incrementation, particularly for semantic variables. I end with further thoughts on how to operationalize change theories into acquisition research, going forward.