One Does Not Simply 'Mm-hmm': Exploring Backchanneling in the AAC Micro-Culture
Tobias M Weinberg, Claire O'Connor, Ricardo E. Gonzalez Penuela, Stephanie Valencia, Thijs Roumen · 2025 · ASSETS 2025: 27th International ACM SIGACCESS Conference on Computers and Accessibility · doi:10.1145/3663547.3746381
Summary
This paper explores how users of Augmentative and Alternative Communication (AAC) technology engage in backchanneling—the subtle verbal and non-verbal signals (like "uh-huh," nods, and facial expressions) that listeners use to show engagement, signal understanding, and maintain conversational flow without taking a full speaking turn. Backchanneling constitutes approximately 19% of spoken dialogue, yet AAC technology creates significant barriers to this fundamental communication behavior: AAC users must visually attend to their devices to compose messages, making it harder to observe conversational partners' cues; typing backchanneling utterances is too slow to be timely; and the pace of conversation often moves past before a backchanneling response can be produced. The lead author, who has been an AAC user for 13 years due to a neuromotor disease, brings lived experience to the research. The study combines a 3-hour co-design workshop with four AAC users (two full-time, two part-time users, all with motor disabilities ranging from mild to profound) and four in-depth interviews with Speech-Language Pathologists (SLPs). The workshop included two activities: an exploration of backchanneling modalities currently used, and paired conversations comparing AAC-to-AAC and AAC-to-non-AAC dynamics. Researchers observed rich multi-modal strategies including eyebrow raises, head nods, wheelchair taps, vocalizations, facial expressions, and creative use of pre-programmed QuickFire phrases, revealing that AAC users develop their own distinct communication micro-culture for listener feedback.
Key findings
The study revealed several critical findings about backchanneling in AAC contexts. First, AAC users develop a unique micro-culture of communication, blending device output with embodied signals like eyebrow raises, chair movements, vocalizations, and facial expressions—strategies that operate "in parallel" to device use without interrupting message composition. Second, backchanneling dynamics differ significantly between AAC-to-AAC and AAC-to-non-AAC pairs. In AAC-to-AAC conversations, both users looked down at their devices simultaneously, leading to near-complete loss of eye contact and missed visual backchanneling cues, creating "simultaneous composition" where both typed at once producing disconnected exchanges. In AAC-to-non-AAC pairs, non-AAC partners relied heavily on echoic backchanneling (repeating the AAC user's last words with rising intonation) and gradually adapted their listening approach over the conversation. Third, collaborative backchanneling emerged as a community practice—when one AAC user encountered a communication breakdown, others filled the gap, with partners acting as interpreters and the group "sharing the load." Fourth, all four SLPs confirmed backchanneling's importance but revealed it is never formally taught in SLP education or therapy—none had a "backchanneling curriculum" and the topic rarely appears in clinical guidelines or software. SLPs noted that timing is the decisive factor, and that non-verbal modalities ("a facial expression or vocalization is quicker than generating a message response") consistently beat device-mediated responses for backchanneling. The SLPs also emphasized the need for partner training to recognize and respond to AAC users' idiosyncratic cues.
Relevance
This research has important implications for AAC technology design, clinical practice, and broader understanding of accessible communication. The central insight—that backchanneling in AAC constitutes a micro-culture with its own norms rather than a deficient version of mainstream backchanneling—reframes how designers should approach AAC communication tools. Rather than trying to make AAC backchanneling match non-AAC norms, technology should support and amplify the existing embodied strategies AAC users have developed. Specific design recommendations include: fast, low-effort backchanneling triggers (eyebrow detection, physiological sensors, vibration cues) that complement typing without interrupting it; customizable expressive shortcuts with emotion-tagged presets rather than one-size-fits-all templates; and partner-aware timing support that visualizes conversational floor dynamics. The finding that SLPs receive no formal training in backchanneling despite its communicative importance highlights an urgent curriculum gap. For the broader accessibility community, this work demonstrates that communication accessibility extends far beyond message transmission speed—it encompasses the full richness of conversational participation including the subtle signals that build rapport, signal engagement, and co-construct meaning.
Tags: AAC · backchanneling · non-verbal communication · micro-culture · listener feedback · speech impairment · motor impairment · co-design · conversational agency · expressive communication