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According to many authors (Cinque 1999, Hacquard 2006, a.o.), epistemic modals in sentences such as “It had to be raining last night” always scope over past tense, expressing a present epistemic claim about a past event. However, there is no consensus on this point: for others (e.g. Rullmann & Matthewson 2018), epistemics can, or even must, scope below tense. This debate has substantial consequences for theories of modals. As of now, research lacks a systematic empirical description of the crosslinguistic picture. The examples discussed in the literature vary widely between languages, and most of the data comes from researchers’ own intuitions, fieldwork involving a limited number of informants, or informal questionnaires. The goal of this paper is, first, to settle the current disagreement on the judgments, by comparing in a more controlled way judgments in three languages, English, Dutch, and French. Second, it is to assess the prediction from Van Dooren (2020b) that there is variation between languages, which can be explained by crosslinguistic differences in modals’ lexical status: (semi-)auxiliaries versus verbs. We report two acceptability judgment experiments testing past tensed epistemic modal sentences’ interpretations in English, Dutch, and French, comparing had-to/moest/devait to the verbs seemed/leek/semblait, using identical sentences and methods and controlling for various factors overlooked in previous studies. We show that (i) epi>tense is available in all languages; (ii) English had-to is overall dispreferred as compared to Dutch moest and French devait. While we only find nuanced support for van Dooren’s proposal, our results open promising avenues for more controlled experimental research on modal-temporal interaction.

This dissertation investigates when and how children figure out the force of modals, that is, when and how they learn that can/might express possibility, whereas must/have to express necessity. Learning modal force raises a logical “Subset Problem”: given that necessity entails possibility, what prevents learners from hypothesizing possibility meanings for necessity modals? Three main solutions to other Subset Problems have been proposed in the literature. The first is a bias towards strong (here, necessity) meanings, in the spirit of Berwick (1985). The second is a reliance on downward-entailing environments, which reverse patterns of entailment (Gualmini & Schwarz, 2009). The third is a reliance on pragmatic situational cues stemming from the conversational context in which modals are used (Dieuleveut et al., 2019). This dissertation assesses the viability of each, by examining the modals used in speech to and by 2-year-old English children, through a combination of corpus studies and experiments testing the guessability of modal force based on their context of use. I show that negative and other downward-entailing contexts are rare with necessity modals, making them impractical on their own. However, the conversational context in which modals are used in speech to children is highly informative about both forces. Thus, if learners are sensitive to these conversational cues, they, in principle, do not need to rely either on a necessity bias nor on negative environments to solve the Subset Problem. Turning to children’s own productions, I show that children master possibility modals very early: by age 2, they use them productively, and in an adult-like way. However, they struggle with necessity modals: they use them less frequently, and not in an adult-like way. Their modal uses show no evidence for a necessity bias. To assess how children actually figure out modal force, and which of the available cues children use to figure out modal force, I then examine which aspects of children’s input best predict their mastery of modals. Preliminary results suggest that negation is predictive of children’s early success with necessity modals, and that frequency of modal talk, but not of particular lexemes, also contributes to their early success.