Dynamic One Hand Chord Keyboard

Jacqueline I. Weller

Department of Informatics and Media, Uppsala University, jacquelineinge.weller.9092@student.uu.se

Portable, handheld, and wearable devices are an integrate part of everyday life, yet there is no well-established text input

method for devices with very small screens. Speech to text has been a quick fix, but entails privacy concerns and can be

obtrusive. Chord keyboards bring various advantages for application in a mobile environment, as they require fewer keys and

can thus be small and portable. The aim of this work is to suggest an alternative to the QWERTY keyboard, suitable for text

entry on devices of all sizes, shapes and mobility requirements. A one hand operational chord keyboard was developed and

evaluated in a small user study with regard to its social acceptability. Learnability showed to be a concern that discourages

use, while social aspects did not seem to be an issue.

Additional Keywords and Phrases: Chord keyboard, Portable devices, Mobile devices, Text input, One-handed

keyboard

ACM Reference Format:

This work was submitted in partial fulfillment for a master’s degree in Human – Computer Interaction at Uppsala University,

Sweden, on the 23rd of August 2021. Permission to make digital or hard copies of all or part of this work for personal or

classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage

and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others

than the author must be honored.

© 2021 Copyright is held by the owner/author(s) acceptance.

1 INTRODUCTION

As wearable and portable devices such as smart phones, smartwatches and fitness bands proliferate all areas

of life, their small-size screens pose challenges concerning even fundamental tasks like text entry [14]. The

ubiquitous QWERTY keyboard in its current form has been established around a century ago and its

arrangement of letters was optimized for mechanical typewriters to avoid jamming of typing bars [12]. While in

the digital age the QWERTY layout, despite not being optimal [7], still works sufficiently well for desktop

computers and remains the primary keyboard for text entry, there is no comparable device or method for text

entry on handheld, wearable and mobile devices [22]. Shrinking the QWERTY layout to fit the miniature screens

of portable devices is often impossible, or, like on smartphones or navigation devices, a tight squeeze, which

results in lower efficiency and increased error rates [9]. In addition, many mobile and portable devices are

designed for one-handed operation, for which the QWERTY layout is far from optimal. Virtual keyboards

furthermore eliminate the touch typing ability (i.e. using muscle memory to type without looking at the keyboard),

which largely contributes to the good typing speeds achieved by experienced typists on a standard QWERTY

keyboard [22]. The loss of the touch-typing ability also means that tasks that involve composing text, like e-mail

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writing and text messaging, are less accessible on the go, as visual attention is required to safely navigate the

environment and can therefore not be devoted to the screen of a smartphone or other portable device. While

almost 50% of pedestrians nevertheless compose text while walking [33], many slow down and some even

stop, which clearly shows that the QWERTY Keyboard does not perform well in a mobile environment.

Although researchers frequently pointed out the need for a more portable keyboard since the 1990s [9, 12,

20, 33], and despite research efforts to find alternatives to the QWERTY, there is still no established alternative.

Speech-to-text or voice recognition have so far commonly been applied as a quick fix, but these technologies

are computationally intensive and more importantly, speaking the text out loud can certainly be obtrusive, poses

privacy concerns and security risks and is therefore often inappropriate [24]. Chord keyboards, offer a multitude

of advantages for application in mobile use. In contrast to the QWERTY keyboard, where keys are for the most

part pressed one at a time and represent one particular character each, chord keyboards do not feature this

one-to-one mapping of keys to characters, instead characters are entered by pressing multiple keys in various

combinations. A trivial example of two-key chords is found in the use of the SHIFT key to capitalize letters on a

QWERTY keyboard, where two keys pressed simultaneously result in a single character. A major distinguishing

characteristic for chord keyboards is that for a given set of characters, they require fewer keys – five keys, with

their 31 combinations in which at least one key is pressed, suffice to enter the 26 letters of the English alphabet

plus five more characters. This means that each key can be increased in size while still keeping the overall size

of the device small enough to be easily portable. Each finger usually only operates one to a few keys, which

brings two advantages: One, touch typing is possible, which permits eyes-free typing, as well as contributes to

increased typing speed [24], and second, fingers for the most part don’t need to travel between keys, which

may results in decreased error rates, as motor load is reduced [12]. Due to the small amount of required keys,

chord keyboards furthermore lend themselves for one-handed operation, which is beneficial for people with

impairments [17, 27, 34] and which makes chord keyboards perfectly suitable for application in a mobile

environment or for tasks where the other hand may be occupied.

1.1 This Study

The aim of this thesis is to propose an alternative to the QWERTY keyboard that is suitable for application in a

mobile environment and for text entry on devices of all sizes, shapes and mobility requirements, in order to

solve the current problems of text entry on handheld, mobile, and portable devices. A prototype of a one-hand

operational chord keyboard was developed for the English alphabet and evaluated in a small user study.

Technology and innovation can however only solve a problem if it is being used, technology adoption is

therefore central to the success of new technology, but has largely been neglected in the evaluation of

alternative keyboard designs [18, 21]. Social acceptability plays a central role in technology adoption [23, 32]

and was therefore chosen as the main aspect for evaluation.

The following background section provides a short overview on the history of chord keyboards and presents

other inventions and designs of chord keyboards, along with their input methods. The development section

describes the process of designing and building the prototype, and motivates design decisions. The methods

section describes the evaluation of the prototype, followed by the results. Finally, its qualities and shortcomings,

as well as possible future developments are discussed.

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2 BACKGROUND

The concept of chord keyboards is by no means new. The first chord keyboard is reported to be Livermore’s

pocket printing machine, invented in 1857 [1]. It featured six keys attached to one side of a cuboid casing,

arranged in two rows of three. While the thumb and little finger were used to hold the device, the index, middle

and ring finger each operated two keys. The entered text was printed onto a small roll of paper. It is reported

that Livermore used his invention to take notes while walking, utilizing it for eyes-free typing and taking

advantage of the chord keyboard’s good portability due to its small size.

A century later, another pertinent system included a chord keyboard. The on-line System (NLS) was

developed and presented by Engelbart and English in 1968 [6] and featured three input devices: a computer

mouse that was novel at the time and was used for spatial tasks such as pointing and selecting elements on

screen, a five key chord keyboard that allowed entering all letters of the English alphabet plus five punctuation

characters, as well as a QWERTY keyboard used for entry of longer sections of text. The chord keyboard was

developed to complement the computer mouse for simultaneous one-handed text input. This setup solved the

problem that alternating text entry with using the mouse required the user to type on the QWERTY with one

hand or constantly move one hand back and forth between mouse and keyboard. By using the mouse to

navigate the text and using the chord keyboard to insert and remove characters, text editing became much

more efficient. The system was supposed to benefit expert users by learning a more optimized system, rather

than making computation more accessible to general public, yet the computer mouse remained the main input

device for personal computers.

An early chord keyboard that is still used today is the braille keyboard [1]. Braille, a reading and writing

system for visually impaired people, is typed by simultaneously pressing a combination of six keys creating a

pattern of up to six haptically perceptible points that define a Braille letter. Here the solution to eyes-free typing

is touch typing on a chord keyboard.

Chord keyboards are, however, not only occasionally found in the history of computation. In the late 19

hundreds, when computers became more attractive to the general public because they were getting smaller

and it was conceivable that computers will become portable, researchers and engineers frequently noted the

need for a more portable alternative to the QWERTY keyboard and developed a number of input methods and

designs, a selection of which is presented below.

The twiddler [10] is a chord keyboard for one handed use featuring 12 keys. While the thumb operates a few

function keys and a joystick that functions as a mouse, the other four fingers operate three keys each, for text

entry. The alphabet is divided into three sections, where the first eight letters are entered with a single keystroke

using one of the keys from the first two columns. The other 18 characters are divided into two sets of nine and

are entered with a two-key chord, meaning that two keys are pressed simultaneously. Each of these chords

involve the index finger, which, similarly to how a mode key works, selects the set of characters that the typed

letter is in, while middle, ring or little finger select the letter. Additionally, the keys in the third column are space,

backspace, delete and enter, when pressed in a single keystroke. Dividing the alphabet into sections and

constraining the chording to two-key chords, where one finger is involved in every chord, allowed the twiddler

to provide hunt and peek, which is not usually achieved by chord keyboards.

Another handheld chord keyboard is the stealthy keyboard [24]. Like the twiddler, the keyboard is designed

for one handed use, with four fingers being used for chording. It features eight keys, and while the idea of having

columns of four keys each is similar to the twiddler, the arrangement is fundamentally different: The keys are

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positioned approximately parallel to the outstretched fingers, facing toward the fingers. Instead of moving the

finger tips between columns, the keys are arranged in such a way that different parts of the fingers are used to

press the keys in different columns. The finger tips are used to depress keys in the outer column (farthest from

the palm of the hand), while keys on the inner column (closer to the palm of the hand) are pressed with the

middle phalanx of the finger. The frame is shaped such that the device is held in place passively and the keying

fingers are not involved in supporting the device in use. As the thumb is not used for typing, it can either be

used to hold the device more firmly, or operate a trackball or joystick as a mouse. The authors emphasize the

importance of the keyboard to be stealthy when stowed and in use and provide a collection of important

characteristics for portable keyboards.

An approach that does not involve switches is taken by Fukumoto and Tonomura [9], instead they use

accelerometers that are attached to each finger in order to detect the deceleration generated by tapping on a

surface such as the knee, thigh, or table. The device is wearable and does not cover the finger tips. Chording

is used for text input, although not all chords require the involved fingers to be tapped simultaneously. To avoid

hard-to-type finger combinations two-stroke chords were included, where fingers touch the surface in quick

succession and the order in which they do so is relevant. The authors found that there is a difference in typing

performance between piano players and non-players, with participants who played the piano being overall about

1.5 times faster than those who did not. In addition, two-stroke chords were easier and more effective for the

group that played the piano, with the fastest chords being a mix of single-stroke and two-stroke chords, while

for the non-piano players the fastest chords only comprised simultaneous chords. This shows that with practice,

two-stroke chords are as effective as single-strike chords, while for novices single stroke chords are easier. The

authors suggest a time tolerance of 15 to 20 milliseconds for simultaneous strokes and an interval of

approximately 120 milliseconds for the tap onsets of two-stroke chords.

The idea of non-simultaneous chording was taken one step further by Miller [27], who proposed a mapping

of characters to chords for a four-key chord keyboard. With the chording method they propose, each chord

involves exactly two keys, whereby the sequence in which they are both pressed and released is decisive for

the inputted character. By making order relevant, the number of characters that can be entered with a given set

of keys can be considerably increased.

3 DEVELOPMENT

The development process was split into three phases. First the research literature was consulted, the most

relevant findings of which are summarized above. The second and third phase comprised the conceptualization

and physical implementation of the prototype respectively, and are described in this chapter. During

conceptualization and based on findings from the literature, a list of relevant and viable qualities was defined to

guide the further design process and to evaluate the final product against. Additionally, some fundamental

decisions concerning the interaction with the device were made, such as the number of actuators. Based on

these decisions, online surveys were used to further inform design decisions about the interaction. Possible

shapes of the device were not considered at this point, as the shape largely emerges from the desired

interaction. The third development phase was about implementing the physical prototype. This phase included

defining the shape, creating the parts, embedding the electronics and programming the keyboard functionality.

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3.1 Qualities

Based on the literature, a set of qualities and desirable characteristics concerning portability, ergonomics,

accessibility, typing speed and error rates, as well as social acceptability was compiled.

Table 1 matches the characteristics with their benefit and source.

Table 1: Characteristics for portable text entry devices

Characteristic Benefit Reference

Flexibility concerning hand size and shape, handedness, and character map

Accessibility [31]

One-hand operational Accessibility, Portability [22, 24]

Orientation independent (orientation and position of arm and hand do not matter for functionality)

Accessibility, Portability [24]

Self-sufficient (no interaction with other objects required for use) Portability [24]

The device is passively held in place, the keying fingers are not involved in holding the device

Typing speed, error rates [24]

Permit touch typing and eyes-free operation Safety, mobility, typing speed [24, 33]

Tactile feedback Error rates [33]

Small movement required to actuate input Ergonomics [15, 25]

Low force required to actuate input Ergonomics [15, 25]

Relaxed finger position in use Ergonomics [24]

Stealthy in use, bystanders cannot observe what is typed Social Acceptance [24]

3.2 Minimal Character Set

Since the intended use of this device is for text entry, text editing functionality such as moving a cursor were

not given weight in the development process. This also delimits the minimum required character set that the

device must provide. The device needs to allow for input of alphanumeric text, consisting of the letters of the

English alphabet, capital letters, numbers and basic punctuation, including in particular space, backspace,

comma, full stop, and line break.

3.3 Interaction Modality and Chord-Key Mapping

A crucial element of the design of a chord keyboard is the interaction with it. This is which actions is the user

expected to perform when using the keyboard. This section will inform the design choices that affect the

interaction.

A pre-study was conducted to evaluate the suitability of tapping onto a surface as method of text input. The

tap was measured using accelerometers that sensed the deceleration occurring when a finger touches the

surface and the downward movement suddenly stops. Plastic clips were used to attach an accelerometer to the

middle phalanx of each finger. Results showed that, with an in the scope of this thesis feasible setup, a tap

cannot be detected with sufficient accuracy, as often times the difference in signal strength between the finger

that actually touched the surface and adjacent fingers is too small to be detected reliably. This finding led to the

decision to use microswitches instead, as the movement can still be quite small and requires low force, but can

be detected with high accuracy. In addition, with microswitches as compared to other possible sensors like

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photosensors, the tactile feedback of actuating an input is retained. However, in contrast to an accelerometer

based solution where the device can sit on the back of one’s hand leaving the fingers and palm free for other

use, when using micro switches the finger tips cannot remain uncovered and the device will most likely be held

in the palm of the hand.

Since this work aims to develop a device that is suitable for one-handed use, and since it is advantageous

to use not more than one actuator per finger, it was decided to only consider designs with a maximum of five

actuators. Even though five binary keys that are activated simultaneously in different combinations can produce

31 distinct outputs and therefore cover the 26 letters of the English alphabet as well as five extra characters,

entering a larger character set including capital letters, numbers, additional punctuation, and characters

occurring in other languages should be possible as well. Therefore different ways to increase the number of

possible combinations were considered: Ternary keys have two on-states and one off-state, thus allowing for

more combinations, however, technical feasibility in the scope of this study was a factor contributing to the

decision against ternary keys. Another method to increase the number of possible combinations was proposed

by Fukumoto and Tonomura [9]. The authors increased the number of combinations by giving the order in which

keys are depressed relevance for the combination. Miller [27] took the idea one step further and additionally

made the release order relevant. The author argues that these ‘composite keystrokes’ are easier to learn, as

characters become associated with a certain movement rather than a specific combination of keys. The difficulty

of simultaneous as well as composite chords was evaluated in online surveys:

Two separate online surveys were used to assess the difficulty of simultaneous and compound chords. After

introducing participants to the topic of research, the surveys listed all possible chord combinations (31

combinations in the survey for simultaneous chords, excluding the state where none of the five keys is

depressed and 40 combinations in the survey for compound chords, resulting from 10 two-key combinations

with four possible press and release orders each). In both surveys participants were asked to perform the

movement of the chord by tapping the respective fingers onto the table before rating the difficulty on a five point

Likert scale. Tapping on the table was chosen as a generic movement to assess the relative difficulty of the

various finger combinations as it is easy enough for the use in an online survey. Both surveys existed in two

versions: The survey for simultaneous chords was split based on what uninvolved fingers do, one asking

participants to let the fingers not involved in the tap rest on the surface, the other asking participants to keep

uninvolved fingers floating in the air. The survey for compound chords was split based on the release order,

one version listing the 20 combinations where the release order is the same as the order in which the fingers

touch the surface (resulting in a rolling movement), and the other listing the 20 combinations where the fingers

are released in the reverse order in which they touch the surface (resulting in a rocking movement). The

simultaneous chords survey was distributed on the subreddit sample size and filled by 250 participants, who

participated voluntarily with no compensation. The questionnaire for compound chords was distributed on

SurveySwap and answered by 50 participants who participated voluntarily and were compensated with website-

specific points to help them get their own surveys answered. Data was excluded from analysis when participants

mentioned that they did not fully understand the questionnaire, or when they gave the exact same difficulty

rating to each chord. All survey templates are shown in appendix D.

The difficulty of different finger combinations was rated on a five point Likert scale, where smaller values

signify easier combinations. The surveys of simultaneous chords showed that keeping uninvolved fingers in the

air is significantly easier than keeping them on the surface (𝑝 < 0.02). For simultaneous chords with uninvolved

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fingers in the air, chords involving adjacent fingers received the lowest difficulty rating (𝑚 = 1.21 ± 0.52), closely

followed by combinations that involve only a single finger (𝑚 = 1.29 ± 0.58). Combinations leaving one finger

uninvolved in between two fingers involved in the chord (i.e. skipping one finger) were found to be the most

difficult (𝑚 = 1.29 ± 0.58), whereby skipping the index finger was the easiest (𝑚 = 1.68 ± 0.85) and skipping

the ring finger the hardest (𝑚 = 3.02 ± 1.37). Even though simultaneous chords were not directly compared to

compound chords in the questionnaires, compound chords received a significantly higher difficulty rating (𝑚 =

2.61 ± 0.16) as compared to simultaneous chords (𝑚 = 1.85 ± 0.78; 𝑝 < 0.0001). The surveys of compound

chords showed that rolling movements (where keys are released in the same order as they are pressed) and

rocking movements (where keys are released in reverse order) are equal in level of difficulty (𝑝 = 0.72).

Furthermore, compound chords showed a significantly smaller standard deviation for mean chord difficulties

(𝐹39,61 = 0.04, 𝑝 < 0.0001). This means that while compound chords are more difficult overall, they are

significantly more homogenous in difficulty level than simultaneous chords.

The finding that simultaneous chords are easier to perform than compound chords as they were suggested

by Miller [27] is in line with the finding that by untrained users, simultaneous chords can be inputted faster than

non-simultaneous ones in the study by Fukumoto and Tonomura [9]. This finding led to the decision to map the

26 characters of the alphabet to simultaneous chords. The five remaining combinations were used for

punctuation and a mode key. To optimize for ease of use and typing speed, the mapping was done such that

character frequency [5] negatively correlates with chord difficulty (i.e. the more frequent a character, the easier

the chord it is mapped to). Table 2 suggests a mapping for the 26 letters of the English alphabet and the most

common punctuation characters. It also provides a mode key to access the rest of the character set, as well as

an ‘escape’ keystroke to return to normal mode or cancel the current input before a character is generated. The

mapping was implemented for testing and is not meant to be final, but can be understood as a possible default

setting that can be changed, expanded and adapted to the user’s specific language, preferences and application

of use.

3.4 Modeling

After the interaction has been established, the shape of the device was being developed through iterating on

the process of 3D modeling and printing. 3D Printing was the method of choice to bring the prototype to life and

to give it a physical shape, as it is an easy and quick way to create three-dimensional objects of various shapes

and sizes and to materialize an idea to make it testable. Also, objects can be printed with reasonably high

accuracy that could not easily be achieved with other methods. This makes movable parts easy to build and

altogether 3D printing offers good creative freedom, as there are only few limitations to the shapes that are

possible to be printed.

A starting point for the design work was the decision that five microswitch keys, each operated by one finger

will be used for input, which already delimited the realm of meaningful designs considerably. To reduce the

strain induced by prolonged usage, the fingers should be close to their resting position during operation [24]

and neither too straight, nor too curled. When the fingers are bent slightly more from their relaxed position, the

fingertips (except for the thumb, which moves perpendicular to the other fingers) move approximately towards

the ball of the hand. This makes the ball of the hand suitable for providing the counterpressure for the actuation

of the micro switch keys. In combination with the aim to make the device as portable as possible, it seemed

reasonable to only consider handheld devices, thereby delimiting the realm of possibilities further.

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Table 2: Character map matching chords and characters. Chord notation is as follows: the position of a symbol determines

the finger (thumb, index, middle, ring, little from left to right), the symbol (‘o’ or ‘.’) indicates whether the respective finger is

involved in the chord, with ‘o’ indicating that the finger is involved and ‘.’ Indicating that the respective finger is not involved

in the chord. For example ‘.oo..’ is the chord that involves index and middle finger, the chord ‘o.ooo’ involves all fingers but

the index finger.

A freely available 3D model of a hand was imported to serve as a point of reference for creating possible shapes

for the prototype. The aim of the first shape modelled was to establish a connection between the fingertips and

the ball of the hand. The model started out as a ring-like shape with a rectangular profile. The top face of the

ring, where the index, middle, ring, and little fingers rest, was flattened and bent outwards (i.e. put at an angle

to the middle axis of the ring) to allow the fingers to rest in a less curled position. The lower part of the ring

which rests in the palm of the hand was widened and also angled so that it lays flat in the hand (see figure 1A).

Mode Normal Control Shift …

Single keystrokes

o.... e

Access t

o

oth

er

mo

des

E .o... SPACE SPACE ..o.. , <lock mode> ...o. . ....o CRL CRL

Two-Key Chords

oo... a

Punctu

atio

n

A o.o.. i I o..o. o O o...o u U .oo.. t T .o.o. m M .o..o f F ..oo. n N ..o.o v V ...oo d D

Three-Key Chords

ooo.. h H oo.o. w W oo..o b B o.oo. p P o.o.o x X o..oo y Y .ooo. s S .oo.o q Q .o.oo k K ..ooo r R

Four-Key Chords

oooo. c C ooo.o z Z oo.oo j J o.ooo g G .oooo l L

Five-Key Chord

ooooo CANCEL ESC ESC

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Printing the model showed that the shape had potential in directing the force of the fingers to the palm of the

hand, while allowing the fingers to be near their resting position, despite it slipping out of the hand too easily

due to the flat contact face and the wide angle between the lower and upper part of the ring. The shape was

refined in multiple iterations. The contact face for both, the fingers and the palm of the hand were rounded,

which resulted in a much better grip. The symmetry was abandoned, to allow for a more ergonomic design,

where the little finger is lower than the index finger and where there is more room for the thenar (i.e. the muscle

connecting thumb and wrist). Also, the ring was closed to a solid shape for more comfort overall. The result was

a rounded organic shape resembling a deformed half sphere (see figure 1B).

While this shape lied in the hand very comfortably in the last iteration and could easily be developed into a

full prototype by adding the electronics, a major drawback was its rigidity. It had a fixed size thus not adjusting

well to different hand sizes and due to its ergonomic shape it could not be used with both hands interchangeably.

However, the value of the model lied in defining an ergonomic and comfortable shape very well and it was used

as a stencil in the development of a more flexible design.

The aim of the next model was to keep the comfort and the ergonomic shape of the first, while adding good

flexibility. For this model some inspiration was taken from McKown [24], who attached the keys to an axle so

that angle and position are adjustable. Also, their keyboard has a frame that passively holds the keyboard in

place leaving the fingers free to operate the switches and not involved in supporting the device, which is a

desired, but as yet missing feature. The first draft, as shown in figure 2A consisted of multiple rough and easy

to print parts: a handpiece provided the contact face to the palm of the hand, with to rods on either side to hold

it in place. An axle was holding four movable parts, each corresponding to one of the fingers not including the

thumb, as its exact position was yet to be determined. Three connecting pieces, each attached between two of

the moving parts, joined the axle with the handpiece. Angle and length of the connectors determined the position

and rotation of the axle with the movable parts. Making the connecting pieces adjustable in length and angle

makes the object adjustable in size and degree of asymmetry, as well as in direction of asymmetry. This enables

an initially symmetrical design to be adjusted to ergonomically fit the left and the right hand and be used by both

interchangeably. A first print with fixed connector lengths showed that this concept had the potential to be

developed into a more flexible solution while retaining the comfortable feel of the first model.

A B

Figure 1: The first model of the device, developing the basic shape. The model started as a ring-like shape (A) and was

refined into a more ergonomic shape (B), here featuring a model for the right hand from the top and from the side.

10

The next iterations focused on achieving the desired flexibility of the connectors, as well as fitting a piece for

the thumb. In a first step, the number of connectors was reduced to two, as this reduces the complexity of the

model and is sufficient to hold the axle in place. After multiple iterations of modeling and printing the mechanic

of the connectors, the solution consisted of a design, with a print-in-place ball joint at the bottom where the

connector is fixed to the handpiece, as well as at the top where the connector is fixed to the axle. This gives

flexibility to the angle of the connector in relation to the handpiece, as well as to the angle of the axle in relation

to the connector (see figure 2B). To allow for the length of the connector to be adjustable as well, it was split

into two parts in the middle. Top and bottom part of the connector could be pushed into each other and locked

in place by rotating them slightly against each other. The locking was achieved through a helical profile of both

the inner and outer part. Through rotation, the part with the larger radius on the inner piece touches the part

with the narrower radius on the outer piece, which leads to jamming, as shown in figure 2D. The position of the

ball joints can be fixated with setscrews. With this mechanism, the top part can be detached and flipped. Due

to this it was possible to have only one thumb piece that is attached to one side of the axle and still allow for

use with either hand.

After the mechanical development was finished, the model was tweaked slightly to fit micro switches and

cables. The final result is shown in figure 2C. For the full iteration of the shape see appendix A.

A B

C D

Figure 2: The development of the model from first draft to final version. The first draft (A) consisted of a handpiece (gray),

an axle (red), four pieces for the fingers that can move around the axle (blue), and three connectors holding the axle

(yellow). In later iterations the connectors were made adjustable in angle and length (B), the mechanism that is used to

adjust the length is shown in (D). The final model contains notches for the electronic parts.

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3.5 Physical Implementation

The 3D models for the prints were created in SketchUp Make 2017 and sliced in Cura 4.8.0. They were printed

out of PLA on the Creality Ender 3 printer. The Arduino Uno board was chosen as the processing unit of the

prototype. While it is not the smallest solution, it was the most easily available one and was chosen for that

reason, as it was not relevant for this prototype to fit all the electronics into the casing. The normally open and

ground pins were used to read the signal of the five micro switches (Type MS-002 BBJ-WK1-01). They each

were connected to the Arduino by soldering a flexible 1mm thick single-core cable directly to the pins of the

switches. The ground pins of all five switches were channeled together into one cable to connect to the ground

pin of the Arduino board. The Arduino was programmed using the Arduino IDE (for the code see appendix B).

To keep the needed electronic parts and the wiring to a minimum, the pins were used as pull-up input pins and

the micro switches were debounced on the software side. Lastly, an adhesive Velcro was attached to the

handpiece to hold the device in place during use without involving the fingers in supporting the device so that

they can move freely.

4 EVALUATION

Alternative keyboard designs are most often evaluated with regard to typing performance based on typing speed

and error rates after a certain amount of training. This way of evaluation however takes a considerable amount

of time and effort, as a considerable amount of participants needs to be trained in several sessions with a

previously implemented training procedure, in order to obtain statistically meaningful data for quantitative

analysis. Performance evaluation was thus out of the scope of this project. Despite there being a number of

alternative keyboard designs that permit a decent typing performance [8, 9, 25, 29], none of them have been

well adopted by the public and become popular in use, indicating that alternative keyboards carry issues

concerning technology adoption. Amongst other factors, social acceptability plays a role in the adoption of new

technology and was chosen as a characteristic for evaluation. While social acceptability has quite early been

identified as an essential element of technology adoption it has not yet been well conceptualized [19], nor has

the term been well defined [19, 28]. Also Davis’ Technology Acceptance Model (TAM) [4] does not account for

social acceptability, which was pointed out as its biggest weakness by Malhotra [23]. In consequence of the

lack of a clear concept, singling out certain aspects that affect social acceptability in a holistic approach is not

possible, instead the social acceptability of individual interfaces is being empirically evaluated.

In psychology things are understood as socially acceptable, if social disapproval is absent [19] and also in

HCI social acceptability has been defined by negation: “A socially acceptable wearable is most notably marked

by an absence of negative reactions or judgments from others.” [16]. Another understanding of social

acceptability is grounded in Goffman’s theory of impression management [11], a sociological concept that

describes people’s endeavors to control the impression others gain through observation, and that uses the

metaphor of a theater with actors and audience to describe public interactions. By analogy, in human-machine

interaction the user takes the role of the actor that performs in front of the audience, personified by the

bystanders. Similarly, Montero et al. [28] describe social acceptability as an aggregate of the user’s internal

impression of performing the action and the spectator’s external impression about the user gained through

observation. This duality influences the use of technology in terms of where, how and if [19].

12

A recent survey by Koelle et al. [19] about methods and measures to assess social acceptability came to the

conclusion that there is no standardized method to assess the social acceptability of a device. However, there

are some similarities in the methods used in previous research. The device and interaction with it is most often

presented in a video, or by letting participants use a prototype. If participants are shown a video they are

generally asked to perform the interaction (e.g. a gesture) as if they were actually using the device. They are

then presented a set of questions about how the interaction feels and in which situations they perceive usage

as socially acceptable. The audience-location scale by Rico and Brewster [32] focuses on who observes the

interaction and where the device is being used. The perspective from which the usage is evaluated can vary

(e.g. being the user themselves or being a bystander watching somebody use the device). The term ‘social

acceptability’ is often rephrased using different adjectives (a list of which is also presented in the paper by Koelle

et al. [19]) to ease understanding of the term for participants. To aid participants imagining themselves in a

certain situation the usage of scenarios is common. Inspired by the scenario generator by Meyer et al. [26],

scenarios specifically adapted to the interaction with this device were created using the software Inkscape (see

appendix E).

Five participants were introduced to the topic of research and were asked to write a few words using the

prototype to familiarize themselves with the interaction. A chord character map in the QWERTY layout (see

appendix F), as well as their input was shown to them on a computer screen. They were then asked to fill in a

questionnaire consisting of a few open-ended questions about their experience, as well as seven scenarios

depicting different use cases (two at home, one at work, two in a cafe and two in public). Each scenario was

paired with four different adjectives (useful, normal, awkward, appropriate) associated with social acceptability

that were taken from Koelle et al. [19] and rated on a five point Likert scale (see appendix G).

The study sowed the potential for versatile use of the device. Participants imagined themselves using it with

their smartphones, tablets, computers or laptops, TVs and gaming consoles, smartwatches were not mentioned.

Two participants generalized its potential application to portable devices and devices with virtual keyboards at

large. Concerning potential locations of use, participants mentioned public and crowded or small spaces, albeit

three mainly imagined themselves using it at home. However, two of the three still rated the device as useful or

very useful and appropriate or very appropriate in the public transport and on the pavement scenarios, while

only one perceived it as not useful and not appropriate in these settings. Four participants perceived the device

as useful and appropriate at the workplace, one could not imagine using it at work. At a café participants did

not perceive the device as particularly useful and while four rated it appropriate with strangers around, only one

did so with family or friends around.

Concerning its application, participants could not only imagine using it for typing, but also for gaming,

although only one mentioned it themself. In the gaming scenarios the device was mostly rated as useful or very

useful and as tendentially appropriate.

The question whether participants could imagine using the device did not yield a homogenous picture, with

one answering ‘likely no’, two answering ‘not really’ and two answering ‘likely yes’. Participants liked the device

for being small, futuristic, and fun, as well as for making one-handed typing easy. The main factor contributing

to participants not imagining themselves using the device however, was concerns about learnability and getting

used to the input motions. Nobody mentioned factors related to social acceptability as a concern that

discourages usage of the device, which is in line with ratings of perceived appropriateness being similar to

13

perceived usefulness. The finding that learnability is a concern is unrelated to social acceptability, yet possibly

the most important finding from the evaluation due to the high degree of agreement on this factor.

5 DISCUSSION

In the first phase of development a number of qualities and desirable characteristics were defined to guide the

further development and are now used for evaluation.

The most important characteristics are portability and flexibility. Portability is mainly achieved through small

size and weight. The main factor contributing to its portability is of course that it designed for use with one hand.

As the device is being held in the palm of the hand with the fingers close to their resting position for better

comfort, the device is not particularly small while in use. Portability is therefore a trade off with comfort and

ergonomic design, as was also noted by Fukumoto and Tonomura [9]. However, contributing to better portability

while maintaining good comfort, is the feature that the device can be folded so that the keys touch the handpiece

and the connectors can be shortened, so that the device is only marginally bigger than the handpiece itself. The

same mechanism makes the device flexible. It allows the design to be adjusted to different hand sizes and

shapes, as well as easily be switched between right and left-hand operation so that both right and left-handed

people can use it equally and it can be used with both hands interchangeably. When walking, it could for

example be used with the dominant hand, while the non-dominant hand could operate it in tasks where the

dominant hand may be used for something else, like operating the mouse for example, like in the setup

proposed by Engelbart and English [6]. The fact that it is a one hand keyboard also contributes to its accessibility

for people with impairments [17, 34]. Another aspect that contributes to accessibility is that the device permits

touch typing. This is beneficial especially for blind users, but seeing users benefit likewise. Touch typing not

only contributes to better typing speeds and decreased error rates, but also makes using the device in a mobile

environment safer, as the full visual attention can be devoted to the surroundings [33].

Good ergonomics were also an important criterion in the design process. The keys are placed in such a way

that the fingers can stay close to their resting position while using the device. Additionally, the use of micro

switches allows for a small displacement of the keycap with low force, which contributes to reducing repetitive

strain injuries [15]. By not using gravity based sensors like accelerometers or gyro sensors but microswitches,

the device can be used equally well in all orientations. This means that the position of arm and hand do not

matter, which contributes to accessibility and portability of the device. The fact that the device has only five keys

means that there is no switching between keys, which eliminates errors due to travelling to the wrong key and

can lead to increased typing speeds. Another quality of the device is its strap, which secures the device in place

so that the fingers are solely responsible for typing and are not involved in holding the device in place. This also

contributes to increased typing speed and lower error rates [24]. Finally, the device is for the most part covered

by the hand, which makes it unobtrusive and contributes to better social acceptability [24].

One issue that is shared by most chord keyboards remains, however, and concerns learnability. As each

key is involved in the production of several letters there is no simple way to permit hunt and peek, which means

that novices need to learn and memorize the mapping of chords to characters before being able to use the

device. This issue also presented itself in the evaluation of social acceptability. A further limitation of this work

is that typing performance, which is central for the success of a keyboard has not been evaluated.

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5.1 The Learnability Issue

Concerns about learnability was the clear answer participants gave to the question of what makes them

reluctant to use the device, which is an issue that has been pointed out before [1]. The twiddler [10] solved this

issue by only using two-key chords, where one key (pressed by the index finger) preselects a set of characters

and the second key (pressed by either middle, ring, or little finger) selects the exact character, much like in a

two stage selection as can be found in [13], except it happens simultaneously. This allows labeling key caps to

permit hunt and peek, but requires far more keys – the twiddler has twelve – to cover the English alphabet.

Studies comparing the learning rates for the QWERTY keyboard with chord keyboards suggest that learning

to type on a chord keyboard does not require more effort than learning to type on the QWERTY keyboard. In a

review of chord keyboards by Noyes in 1983 [29] learning curves of a chord keyboard seem comparable to the

learning curves of a standard typewriter. Likewise, the comparison of the QWERTY keyboard with a chord

keyboard featuring eight ternary keys by Fathallah [7] did not yield a significant difference in learning rates.

Learning rates with a wearable device also showed to be comparable with learning rates on the QWERTY

keyboard, with an input speed of 17 words per minute after ten hours of training with the Chording Glove [20],

as compared to 20 words per minute on a QWERTY keyboard after twelve hours of training [30]. However, in

a comparison of a ten-key chord keyboard with a standard typewriter, Conrad and Longman [3] found the

learning rates to be higher for the chord keyboard in the first two weeks and equal later on. Increased learning

rates on a chord keyboard as compared to the standard QWERTY keyboard were also reported by Gopher and

Raij [12], who trained completely inexperienced typists to type the 22 letters of the Hebrew alphabet on a ten-

key chord keyboard or the QWERTY keyboard and compared typing performance after each training session.

At the end of the training participants reached an average typing speed of 42 words per minute on the chord

keyboard and 24 words per minute on the QWERTY keyboard. In addition, the authors found that while learning

the chords of the chord keyboard and learning the position of the keys on the QWERTY keyboard required the

same time, typists on the chord keyboard did not refer back to the letter chart after the first hour of training,

while typists on the QWERTY continuously looked at the keyboard.

However, when discussing the learnability of chord keyboards, it must be taken into consideration that in the

digital age we live in, typing on the QWERTY keyboard is taught to children at around the age when they learn

to read and write [2]. This means that nearly nobody is new to typing when considering an alternative keyboard

design. Consequently, the comparison of learning rates between chord keyboards and the QWERTY keyboard

may not be as relevant as the assessment whether the effort required to learn how to type with an alternative

keyboard is worth the benefits that the alternative design offers. Future research should consider this

assessment. Based on the findings in this study, users do see the benefits of a small size keyboard and are

open to alternatives to the QWERTY keyboard, but only if convenience in terms of typing speed and ease of

use, which includes learning how to use it, are not sacrificed.

5.2 Future Directions

Even though the presented device is promising in many aspects, there is still room for improvement in structure,

functionality and features, especially as it is a prototype. The overall one-handed operability – which is important

in regard to accessibility – can be improved, as two hands are currently needed for adjusting and handling the

device. The strap, which is put around the back of the hand to hold the device in place can be replaced with a

semi-rigid gooseneck, the shape of which can be individually adjusted. This way, when picking up the device,

15

it is automatically held in place instead of requiring the other hand to secure it in place first. The mechanisms

used to move the axle are in part very rigid, due to the use of screws. Locking, unlocking and adjusting the axle

should be simplified and made possible with one hand.

The prototype was limited to simultaneous chords, but adding compound chords to the functionality is

potentially beneficial: The finding in this study that simultaneous chords are easier than compound chords is in

line with the finding of Fukumoto and Tonomura [9], who found that for untrained users 27 of the 29 fastest

chords are simultaneous chords, with the 16 fastest solely being simultaneous chords. However, for

experienced users this pattern changes, with 13 of the fastest 33 chords being compound chords. In

combination with the finding by Feit and Oulasvirta [8], who conclude that typing speed can be increased by

about 30% through the use of n-grams (i.e. commonly accruing character sequences like ‘ing’, ‘th’ ‘ment’), this

suggests that experienced users can benefit from complementing simultaneous chords used for single-letter

text entry with compound chords for entry of n-grams.

To accommodate for other languages than English, the mapping of chords to characters can be adjusted

and a mode for entering language specific characters can be introduced, as suggested by Miller [27]. While the

prototype was connected via cable, a finished product should of course support a wireless connection, for

example via Bluetooth. A display could be added, to the front side of the device to permit reviewing the written

text. By adding a display, the mapping can, in addition, be completely customizable, which could not only be

used by expert users for more effective use (for example by customizing n-grams or shortcuts), but makes the

keyboard a generic input device with various applications. It could for example be used as a gaming controller,

or potentially serve as a utility for people with impairments (who could for example use it to control a wheelchair).

The device could possibly support saving a number of custom mappings to quickly switch between different

areas of application.

5.3 Conclusion

Inputting text on small portable, handheld and wearable devices is challenging, as there is only little space

available to fit a keyboard. The QWERTY keyboard is too bulky for portable applications and the buttons of

virtual keyboards are often very small, which makes using them cumbersome. Speech to text is a work around

that brings its own problems, such as privacy concerns. This work proposed a design of a one hand operational

five-key chord keyboard in form of a prototype, to meet the requirements for text entry on mobile, portable,

handheld, and wearable devices while on the go. Portability, accessibility, ergonomics, and typing performance

were taken into consideration in the development process. The prototype was created using 3D printing and an

Arduino board. It was evaluated in a small study with five participants in regard to its social acceptability. While

social aspects did not seem to be a concern that discourages usage, having to learn the mapping of chords to

keys did deter participants from wanting to use it. The study showed that users are open to alternative keyboard

designs, as long as convenience and ease of use are maintained.

ACKNOWLEDGMENTS

First and foremost I would like to thank my supervisor Lars Oestreicher, without whom this work would not have

been possible. He gave new inspiration and food for thought when the next step did not seem clear and always

took his time during supervision meetings to give the best support possible. I would also like to thank Annika

Waern for the well done organization of the course and for guiding us through the process of writing a thesis.

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REFERENCES

[1] Buxton, B. 2013. Case Study 2: Chord Keyboards. Haptic Input.

[2] Cicerchia, M. and Freeman, C. Teaching kids to type. Retrieved September 04, 2021 from https://www.readandspell.com/teaching-kids-

to-type.

[3] Conrad, R. and Longman, D.J.A. 1965. Standard Typewriter Versus Chord Keyboard – An Experimental Comparison. Ergonomics. 8, 1

(1965), 77–88. DOI:https://doi.org/10.1080/00140136508930777.

[4] Davis, F.D. 1986. A Technology Acceptance Model for Empirically Testing New End-User Information Systems: Theory and Results.

PhD Thesis, Departmentof Industrial Engineering, Wayne State University, submitted to the Sloan School of Management.

[5] Dickens, M. 2009. Letter Frequency. Retrieved February 12, 2021 from https://mdickens.me/typing/letter_frequency.html.

[6] Engelbart, D.C. 1986. Workstation History and the Augmented Knowledge Workshop. Proceedings of the ACM Conference on the

History of Personal Workstations (1986), 73–83.

[7] Fathallah, F.A. 1988. An Experimental Comparison of a Ternary Chord Keyboard with the QWERTY Keyboard.

[8] Feit, A.M. and Oulasvirta, A. 2014. PianoText: Redesigning the Piano Keyboard for Text Entry. Proceedings of the 2014 Conference on

Designing Interactive Systems (New York, NY, USA, 2014), 1045–1054.

[9] Fukumoto, M. and Tonomura, Y. 1997. “Body Coupled FingerRing”: Wireless Wearable Keyboard. Proceedings of the ACM SIGCHI

Conference on Human Factors in Computing Systems (New York, NY, USA, 1997), 147–154.

[10] George, C.S. 1993. Cybernetic interface for a computer that uses a hand held chord keyboard. 1993.

[11] Goffman, E. 1978. The presentation of self in everyday life. Harmondsworth London.

[12] Gopher, D. and Raij, D. 1988. Typing With a Two-Hand Chord Keyboard: Will the QWERTY Become Obsolete? IEEE Transactions on

Systems, Man and Cybernetics. 18, 4 (1988), 601–609. DOI:https://doi.org/10.1109/21.17378.

[13] Grossman, T. et al. 2015. Typing on Glasses: Adapting Text Entry to Smart Eyewear. Proceedings of the 17th International Conference

on Human-Computer Interaction with Mobile Devices and Services (New York, NY, USA, 2015), 144–152.

[14] Gupta, A. and Balakrishnan, R. 2016. DualKey: Miniature Screen Text Entry via Finger Identification. Proceedings of the 2016 CHI

Conference on Human Factors in Computing Systems. Association for Computing Machinery. 59–70.

[15] Hargreaves, W. et al. 1992. Toward a More Humane Keyboard. Proceedings of the SIGCHI Conference on Human Factors in

Computing Systems (New York, NY, USA, 1992), 365–368.

[16] Kelly, N. and Gilbert, S. 2016. The WEAR Scale: Developing a Measure of the Social Acceptability of a Wearable Device. Proceedings

of the 2016 CHI Conference Extended Abstracts on Human Factors in Computing Systems (New York, NY, USA, 2016), 2864–2871.

[17] Kirschenbaum, A. et al. 1986. Performance of Disabled Persons on a Chordic Keyboard. Human Factors. 28, 2 (1986), 187–194.

DOI:https://doi.org/10.1177/001872088602800207.

[18] Koelle, M. et al. 2018. (Un)Acceptable!?! Re-Thinking the Social Acceptability of Emerging Technologies. Extended Abstracts of the

2018 CHI Conference on Human Factors in Computing Systems (New York, NY, USA, 2018), 1–8.

[19] Koelle, M. et al. 2020. Social Acceptability in HCI: A Survey of Methods, Measures, and Design Strategies. Proceedings of the 2020

CHI Conference on Human Factors in Computing Systems. Association for Computing Machinery. 1–19.

[20] Lee, S. et al. 2002. Designing a Universal Keyboard Using Chording Gloves. Proceedings of the 2003 Conference on Universal

Usability (New York, NY, USA, 2002), 142–147.

[21] Luborsky, M.R. 1993. Sociocultural Factors Shaping Technology Usage: Fulfilling the Promise. Technology and disability. 2, 1 (Jan.

1993), 71–78. DOI:https://doi.org/10.3233/TAD-1993-2110.

[22] MacKenzie, I.S. and Soukoreff, R.W. 2002. Text Entry for Mobile Computing: Models and Methods,Theory and Practice. Human–

Computer Interaction. 17, 2–3 (2002), 147–198. DOI:https://doi.org/10.1080/07370024.2002.9667313.

[23] Malhotra, Y. and Galletta, D.F. 1999. Extending the technology acceptance model to account for social influence: theoretical bases and

empirical validation. Proceedings of the 32nd Annual Hawaii International Conference on Systems Sciences. 1999. HICSS-32.

Abstracts and CD-ROM of Full Papers (1999), 14 pp.-.

[24] McKown, J.W. 2002. Stealthy keyboard. 2002.

[25] McMulkin, M.L. and Kroemer, K.H.E. 1994. Usability of a one-hand ternary chord keyboard. Applied Ergonomics. 25, 3 (1994), 177–

181. DOI:https://doi.org/https://doi.org/10.1016/0003-6870(94)90016-7.

[26] Meyer, H. et al. 2019. A Scenario Generator for Evaluating the Social Acceptability of Emerging Technologies. Human Computer

Interaction and Emerging Technologies: Adjunct Proceedings from. (2019), 101.

[27] Miller, M. 2005. Miniaturized 4-key computer keyboard operated by one hand. 2005.

[28] Montero, C.S. et al. 2010. Would You Do That? Understanding Social Acceptance of Gestural Interfaces. Proceedings of the 12th

International Conference on Human Computer Interaction with Mobile Devices and Services (New York, NY, USA, 2010), 275–278.

[29] Noyes, J. 1983. Chord keyboards. Applied Ergonomics. 14, 1 (1983), 55–59. DOI:https://doi.org/https://doi.org/10.1016/0003-

6870(83)90221-1.

[30] Noyes, J. 1983. The QWERTY keyboard: a review. International Journal of Man-Machine Studies. 18, 3 (1983), 265–281.

DOI:https://doi.org/https://doi.org/10.1016/S0020-7373(83)80010-8.

17

[31] Oestreicher, L. Non-Excluding Design - Designing to Exclude as Few People as Possible. Unpublished.

[32] Rico, J. and Brewster, S. 2010. Usable Gestures for Mobile Interfaces: Evaluating Social Acceptability. Proceedings of the SIGCHI

Conference on Human Factors in Computing Systems. Association for Computing Machinery. 887–896.

[33] Tarniceriu, A.D. et al. 2013. The Effect of Feedback on Chord Typing. Proceedings of The Seventh International Conference on Mobile

Ubiquitous Computing, Systems, Services and Technologies. (2013).

[34] Yeo, H.-S. et al. 2017. Investigating Tilt-Based Gesture Keyboard Entry for Single-Handed Text Entry on Large Devices. Proceedings of

the 2017 CHI Conference on Human Factors in Computing Systems. Association for Computing Machinery. 4194–4202.

APPENDICES

A Iterations on the Model

3D Models were created in SketchUp. The iterations on the shape are shown below

First Iteration

• defining the general structure

Second Iteration

• reducing the number of connectors to two

• refining the handpiece

• introducing symmetry

Third Iteration

• adding a piece for the thumb

• refining the connectors for more flexibility

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Fourth Iteration

• adding a notches for the electronic parts

• refining the handpiece

B Arduino Program Code

Arduino Program Code.pdf

C Examples for Simultaneous and Compound Chords

Each chord is notated in square brackets, where the position of a symbol indicates the finger [thumb, index,

middle, ring, little] and the symbol indicates the action (‘o’ indicates the finger is pressed simultaneously with

other fingers, ’-’ indicates the finger presses and releases the key first, ‘=’ indicates the finger presses the key

first and releases it second, ‘<’ and ‘>’ indicate the finger presses the key second).

In a simultaneous chord, all keys are pressed simultaneously.

Example: [.o.oo]- Index, ring, and little finger press the key simultaneously

A compound chord always involves two keys, where the sequence of both pressing and releasing is relevant.

In this way, there are four possible combinations for the same two fingers.

Example:

Consistent release order (rolling movement)

[.->..] – Index finger pressed, middle finger pressed, index finger released, middle finger released

[.<-..] – Middle finger pressed, index finger pressed, middle finger released, index finger released

Reverse release order (rocking movement)

[.=>..] – Index finger pressed, middle finger pressed, middle finger released, index finger released

[.<=..] – middle finger pressed, index finger pressed, index finger released, middle finger released

D Questionnaires Used for Evaluation of Chord Difficulties

Simultaneous chords with uninvolved fingers in the air

Simultaneous chords with uninvolved fingers on the surface

Compound chords with consistent release order (rolling movement)

Compound chords with reverse release order (rocking movement)

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E Usage Scenarios for Evaluation of Social Acceptability

Scenarios were created in Inkscape and composed of variations of different elements, as shown below:

Purpose of use:

Messaging Gaming Office work

Location of use:

At Home At Work In Public Transport

At a Cafe In Public

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Bystanders:

Family or Friends Colleagues Strangers The User

21

Scenarios Used:

At home gaming alone At home gaming with friends or

family

At work using the computer with

colleagues around

At a café with friends or family text

messaging somebody else

In In a café around strangers text

messaging somebody else

In public transport around strangers

text messaging

On the pavement around strangers

text messaging

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F Character Map Used During Evaluation

G Questionnaire Used for the Evaluation of Social Acceptability

Social Acceptability Questionnaire.pdf