Expressing the confidence level of a system's suggestions by using speech sounds is an important cue to users of the system for perceiving how likely it is for the suggestions to be correct. We assume that expressing confidence levels by using human-like expressions would cause users to have a poorer impression of the systems than if artificial subtle expressions (ASEs) were used when the quality of the presented information does not match the expressed confidence level. We confirmed that this assumption was correct by conducting a psychological experiment.
