We present a new experimental paradigm for investigating lexical expressions that convey different strengths of speaker commitment. Specifically, we compare different evidential contexts for using modal devices, epistemic discourse particles, and statements with no evidential markers at all, examining the extent to which listeners' interpretations of certain types of evidential words and their judgments about speaker commitment differ in strength. We also probe speakers' production preferences for these different devices under varying evidential circumstances. The results of our experiments shed new light on distinctions and controversies that play a key role in the current theoretical literature on the semantics and pragmatics of modals and discourse particles. Our paradigm thus contributes to a domain of experimental research on evidential expressions that is only just taking shape at the crossroads of theoretical semantics/pragmatics and psycholinguistics; we provide a potential starting point for approaching theoretical debates on the nature of modal evidential expressions from an experimental and context-oriented perspective.