Single Switch Communication

For people living with severe motor impairments, Augmentative and Alternative Communication (AAC) devices with a single-switch input can provide a means of computer interaction. Users control the activation time of their single switch by, e.g., pressing a button, releasing a puff of air, or blinking. These switch activations are commonly sent into an AAC interface, such as a scanning system, which facilitates computer navigation or text composition.

Row Column Scanning https://www.wikiwand.com/en/Switch_access_scanning

In a scanning system, individual interface options or sets of options are highlighted in a fixed sequence. To select something, the user waits for their target to be highlighted and then activates their switch. A common approach, row column scanning, involves an activation to select a set of options arranged in a row followed by a second activation to select a column. Such scanning systems are typically limited to displaying options in a fixed grid and, when used for text composition, have extremely slow text entry rates — on the order of 0.3–2.9 words per minute (wpm) and 1.9 wpm — with motor impaired users.


What is Nomon? Our interface, Nomon, addresses the limitations of traditional single switch input methods through its flexible selection scheme. Nomon has many potential uses such as drawing, general operating system control, and even gaming. The interface places an indicator next to each option and uses a probabilistic selection mechanism. This selection mechanism incorporates prior information on options and a model of user-input noise to perform Bayesian updates that adapt its selection criteria to a user’s ability. This adaptation helps the user type quickly while avoiding errors. Further, Nomon is not limited to a strict grid layout as these indicators can be placed at arbitrary locations on the screen

Video demonstration: typing text with the Nomon keyboard application.

How does it work? In Nomon, all options have a clock indicator to their left which allows for selection. Each clock has a unique phase, and the minute hands of all clocks rotate at a constant, shared speed. A user can select an option by clicking when the clock adjacent to their desired option passes noon. The user needs to look only at the adjacent clock to select its corresponding target. After a click, all the clock hands change phase. This phase change is done such that the hour hands on the most likely clocks are maximally separated. The user then repeatedly clicks when the minute hand passes noon until their target is narrowed down and selected. The number of clicks required to select a target is dependent on the precision of the user and on how probable the target is. In a writing application that makes use of a language model, an experienced user can select targets in around two clicks. A demonstration of how typing with the Nomon interface works is included below.

Video: A deep dive into Nomon's unique, probabilistic selection mechanism.


We provide three demos of the Nomon interface below: (1) a Guided Tutorial on selecting items with Nomon clocks, (2) an Emoji Selection Interface that demonstrates Nomon's ability to select between many options at once, and (3) a full Text Keyboard with word completions.




Initial Study

Nomon Technical Report

CHI '22 Performance Evaluation

CHI '22 Interactivity Demo

Tamara Broderick and David J. C. MacKay

Tamara Broderick

Nicholas Bonaker, Keith Vertanen,
Emli-Mari Nel, and Tamara Broderick

Nicholas Bonaker, Keith Vertanen,
Emli-Mari Nel, and Tamara Broderick

GNOMON (Gaming)

Sebastián Aced López, Fulvio Corno, and Luigi De Russis


Active JavaScript Repository

Unsupported Python Repository

Installable Electron App Coming Soon!


Nicholas Bonaker

Graduate Student, MIT

Emli-Mari Nel


Keith Vertanen

Associate Professor, Michigan Tech

Tamara Broderick

Associate Professor, MIT