Easy to Hear, Easy to Select?: Investigating Speech Rate as a Potential Deceptive Pattern in Non-Native Users’ Decision-Making

Voice user interfaces (VUIs) increasingly mediate everyday decision-making, raising concerns about deceptive patterns (dark patterns) in voice-based interactions. Prior work has shown that voice features can influence users' choices, but such effects have mainly been examined in users' native languages. In practice, however, users may need to interact with VUIs in a non-native language, where subtle differences in speech presentation may be harder to resist. This study examined speech rate as a potential deceptive pattern in non-native voice interactions. We conducted three experiments with Japanese non-native English speakers to investigate whether manipulating the speech rate of synthetic speech when presenting options could bias users' selections. The results showed that speech rate manipulation did not clearly bias selections. However, they also indicated that further investigation is needed when the difference in speech rate is more pronounced.