Would People Mumble Rap to Alexa?

Unclear speech, like mumbling, is difficult to understand for people, and even harder for conversational user interfaces (CUI) to process. Yet, there are multiple reasons why unintelligible speech is meaningful between humans, playing a critical role in social dynamics and status signaling that evolved in humans over time allowing us to form cohesive social groups for survival. For example in modern times, humans often use such changed speech in order to make themselves understandable only by in-group members, e.g. "mumble rap", while subtly excluding out-group members. As such, we argue here that future CUIs must be attentive to how people use various forms of non-standard changed speech (e.g. mumbling, dialect, slang, inflection) to express themselves, lest CUIs be socially inept. Based on psychological, linguistic, and cross-cultural research, we point out several major challenges for researchers: 1) current CUIs typically omit non-standard speech like mumbling which are critical to human social communication, and 2) in the future humans may innately form ingroups with their personal CUIs resulting in speech behaviors meant to exclude outgroup members (both humans and machines). Both of those challenges require more research to address. Moreover, the use of changed speech for status signaling and ingroup/outgroup (IG/OG) signaling appears to be a phenomenon that varies across diverse cultures, languages, and situations, which CUI designers and engineers need to be mindful of going forward.