Conflicting constraints on the interpretation of modal auxiliaries

The Dutch modal auxiliaries kunnen ‘can’ and moeten ‘must’ can be interpreted in different ways: ‘participant-internal, ‘participant-external’, and epistemic. For each of the verbs, we assume a basic, default interpretation: ‘participant-internal’ for kunnen, ‘participant-external’ for moeten. In sentences with a ‘neutral’ main verb like zwemmen ‘to swim’, and with a third person subject, the hearer chooses this basic interpretation. We subsequently show that other elements in the sentence can induce a non-basic interpretation. In particular the controllability of the activity expressed in the main verb (‘to swim’ versus ‘to pee’), progressive aspect, and person of the subject (in particular second person subject) are relevant factors influencing the interpretation of the modal verb. We model the factors influencing the interpretation as violable constraints in an optimal theoretic analysis, which leads to tableaux with a sentence as input and an optimal interpretation of that sentence as output.