Clifton, C. , Frazier, L. & Yacovone, A.
University of Massachusetts Amherst
A speaker's knowledge state ('epistemic state') affects the judged naturalness of sentences: 'Jeff or Tim arrived' is less natural than 'Jeff and Tim arrived.' Knowing that an event occurred without knowing its agent is somewhat unlikely. As expected on this account, the penalty for the disjunction significantly decreases in future tense sentences. The penalty thus appears to be a pragmatic effect of accommodating the speaker's unlikely epistemic state. Two new experiments provide further evidence for this interpretation. In Experiment 1, 40 Mechanical Turk workers provided naturalness judgments of 20 sentences, half with disjunctive and half with conjunctive subjects. When these sentences were embedded under a psych or communication verb (e.g., 'Dan thought that Jeff or Tim arrived'), the disjunctive penalty was less than when the sentences were not so embedded (1.61 vs 2.69 points on the 7-point naturalness scale). Experiment 2 demonstrated a similar effect of adding a modal verb (e.g. 'must have'): adding the modal significantly reduced the disjunction penalty (1.61 vs 2.06). Presumably the modal or the psych verb signals the ignorance or incomplete knowledge of the speaker. Without such guidance, language users find it unnatural to have to accommodate a speaker's unlikely epistemic state.