Revisiting the epistemic gap: It’s not the thought that counts

This paper revisits the longstanding observation that children produce modal verbs (e.g., must, could) with their root meanings (e.g., abilities, obligations) by age 2, typically a year or more earlier than with their epistemic meanings (e.g., inferences). Established explanations for this “Epistemic Gap” argue that epistemic language production is delayed because small children can only reason about root meanings. However, root and epistemic uses of modal verbs also differ syntactically and in input representation. We present a corpus study on 17 English-learning children and their input, exploring early productions with both epistemic modal verbs and grammatically simpler and more frequent epistemic adverbs (e.g., maybe, probably). Results show that children use remarkably adult-like epistemic adverb sentences from even before age 2, when they are only producing modal verbs with root meanings. The Epistemic Gap is not well explained by general conceptual advancements. Instead, our data suggest input attestation and ease of form-to-meaning mapping may influence early child epistemic language. These findings are furthermore consistent with cross-linguistic differences in the timing of first epistemic uses of modal verbs, and with recent advancements in our understanding of infant and toddler modal reasoning abilities.