CHAPTER 1 Introduction
1.4 Dissertation Organization
This chapter has illustrated potential value of an appropriated text entry system for persons with motor disabilities. The organization of the paper is as follows:
Chapter 2 describes previous studies and its relation to on-screen keyboard design.
The difficulties of text entry for motor-impaired individuals are explored and the general concept, researches, and the applications of on-screen keyboards are discussed.
Besides, the philosophy of designing for dynamic diversity is also under discussion in this chapter.
Chapter 3 details the core design of D3 on-screen keyboard, including several selection methods, layouts design and the strategies of enhancing control. Section 3.2 describes three innovated selection methods integrated in D3 on-screen keyboard.
Section 3.3 describes layouts arrangement and keyboarding methods. Section 3.4 illustrates layout adaptation program, macro layout, visual prompt layout and keyboard-emulated mouse.
Chapter 4 introduces the usabilitities of D3 On-screen keyboard, which includes the coded selection method, the scanning selection method, and the point-and-click selection method. The results show the benefits by using D3 on-screen keyboard.
Chapter 5 presents the feasibility of utilizing D3 On-screen keyboard for persons with severe motor disabilities. Results from the intervention of 4 clients demonstrated
D3 On-screen keyboard superiority to prior text entry methods of the individual used.
Chapter 6 discusses and concludes this dissertation by summarizing the application of D3 On-screen keyboard for participants and outlining the insights gained from this research as well as suggesting future research.
CHAPTER 2
Literature Review
Computers can help disabled persons with many activities. The advancement of assistive technology has shown its potential to enable disabled students to access the computer. For persons with severe motor disabilities, an on-screen keyboard can be an effective text entry system. In this chapter, the author will discuss the literatures about the issues of on-screen keyboards design. In section 2.1, the author will introduce the difficulties of text entry for persons with motor disabilities. The common features of some on-screen keyboards are delineated in section 2.2. In section 2.3, we will describe the design issues of on-screen keyboards. Finally, the principles of designing for dynamic diversity will be reviewed in section 2.4.
2.1 The Difficulties of Text Entry for Persons with Motor Disabilities
The keyboard and the mouse are the common interaction devices for text entry.
The use of these devices requires a certain level of physical ability which demands precision and motor coordination. Persons with motor disabilities have the same
desire to use computers as ordinary people, but do not have the ability to efficiently use the standard keyboard and the mouse. Access problem, fatigue degree and typing accuracy are the key factors tampering the performance of text entry task for persons with motor disabilities (Trewin & Pain, 1999). Besides, the barriers prohibiting individuals with motor disabilities from using standard keyboard include the disability to access all keys on a standard keyboard and press keys simultaneously; having slow rate of typing, typing with inaccuracy, and quick release of keys.
When these people were asked to use a traditional keyboard to fulfill the typing tasks, several performance errors were observed, including long key press errors, dropping errors, additional key errors, missing key errors and Bounce errors (Trewin
& Pain, 1999). A long key press error is an alphanumeric key which was pressed for the time longer than the default key repeat delay. The types of dropping errors are the user failing to press two keys simultaneously (e.g. the use of the Shift key). An additional key error is a key adjacent to the intended key activated. In the majority of
such errors, both the intended and additional keys are pressed, and the key presses overlap in time. Bounce errors are that the user unintentionally presses the intended key more than once. Missing key errors occur when the users fails to activate their intended key, either because they missed it, or they did not press it hard enough.
For a user who has difficulties in accessing a standard keyboard, many solutions
to a better control of the computer could be applied. A proper seating or positioning system can facilitate hand function. For some users with mild physical disabilities, by adjusting their seating and the displayer position or providing an adjustable table is sufficient enough. Other people with motor disabilities that are able to target individual keys, alternative keyboards come in aid. The alternative keyboards include the chorded, the expanded, the miniature and the ergonomic ones.
For some persons with disabilities who choose to use the standard keyboard and mouse, there are many modifications that can improve their accessibility.
Accessibility features are being gradually incorporated into the operating system to address people with disabilities. The accessibilities features include display magnifier, narrators and on-screen keyboards to suit individuals’ needs. The operating systems also provide accessibility settings to configure the keyboard. Setting the sticky keys allow users to perform key presses involving multiple keys. Setting the key repeat delay can control the length of time a key held down before it repeats. Configuring the debounce time can be introduced to filter out the unwanted key press caused by tremor.
Some individuals with severe physical disabilities without sufficient individual fingers to press the keys are unable to use a standard keyboard and the alternative keyboards. They often require special devices to aid themselves when performing
computer tasks. The use of Graphical User Interfaces (GUIs) has made software more accessible than keyboards primary input devices for motor-impaired persons. An on-screen keyboard allows them to enter data by using an alternative device.
The main groups that use on-screen keyboards are the people with spinal cord injuries, or inability resulting from muscular dystrophy, or cerebral palsy. However, the operating systems embedded in on-screen keyboards are at a basic level. Some commercial on-screen keyboards support advanced level can meet individual’s needs.
2.2 Reviews of On-screen Keyboards
A number of on-screen keyboards can be used to modify the way the keyboard meets users’ special needs. All on-screen keyboards are designed with several selection sets for text entry task. These generally support various selection methods including point-and-click, dwell and scanning. The point-and-click is preferred by most people since it is suitable for people with limited movement range who cannot reach across the standard keyboard. When the user who is unable to press a button or switch can keep the pointing device steady for a short time, dwell selection is an alternative solution. If point-and-click and dwell are too tiring for an individual, switch-based scanning is typically used by persons with severe motor disabilities.
In addition to supporting multiple selection methods, many on-screen keyboards
support advanced features for improving speed and ease of use, including automatic start-up, saving and loading user settings, control over applications and sound actions.
This session reviews and compares a number of on-screen keyboard programs in common use. The available on-screen keyboards are not all reviewed because of its great quantity.
2.2.1 WiViK
WiViK is a commercial on-screen keyboard that provides text entry task for Microsoft Windows operating systems for persons with disabilities. Figure 2-1 and Figure 2-2 show some layouts of WiVik on-screen keyboard. It allows all pointing device to be used to enter text into any application. WiVik on-screen keyboard provides access by using point and click, dwell or switch-based scanning. The text entry technique can be improved in many ways. One improvement is the use of word completion schemes to reduce the number of key presses needed for typing. The program could be customized for letter arrangement, label fonts and spacing.
WiViK also supports integrated abbreviation expansion and speech output to increase the performance. One of the specific features is the configurable switch-based scanning that allows users to use the scanning strategy by choosing the number of switches. The user could use six switches at most to control the system.
Figure 2-1 Wivik on-screen keyboard with complete QWERTY layout
Figure 2-2 Wivik on-screen keyboard with frequency-of-use layout
2.2.2 The Grid
The Grid is an integrated tool for augmentative communication and computer access. As shown in Figure 2-3 and Figure 2-4, the layout of the Grid is divided into rectangles and each individual rectangle could contain images and words. A layout of the
Grid could hold from just 2 cells to over 2000 cells. There are many macros templates
providing common functions for applications such as word processing, internet browser,
mouse control, calculator and media player. The Grid supports between 1 and 8 switches
Figure 2-3 The Grid on-screen keyboard with images layout
Figure 2-4 The Grid on-screen keyboard with frequency-of-use layout
2.2.3 Click-N-Type
The Click-N-Type is a free on-screen keyboard. Figure 2-5 provides the layout of Click-N-Type program. The Click-N-Type on-screen keyboard has many user customizable layout options that allow users to design their own keyboards. A QWERTY layout now comes with the basic package, featuring macros for typing words or phrases with one click. Multilingual capability and complete language packs for traditional Chinese, German, French and British keyboard layouts are available as
add-ons. There is optional audible feedback as a user type, word-prediction and word completion capability. User can use right-click and press Shift to type a single shifted character. It also includes is a nonstick Shift key option for Auto Click and head-pointer users.
2.2.4 SofType
SofType is commercial on-screen keyboard and compatible with Windows operating system. The on-screen keyboard offers a choice of twelve different keyboard layouts (some layouts as shown in Figure 2-6). Most of these layouts have the same basic appearance of QWERTY keyboard. In addition, it is possible to edit an existing layout using a text editor. SofType has a control option that allows the user to adjust the size of the keys and the interval between the keys. Increasing the size of the keys and the interval between keys makes it easier to hold the pointer on the desired key when
Figure 2-5 The layouts of Click-N-Type on-screen keyboard
When AutoClick is enabled, clicking functions are performed by holding the pointer motionless for a programmable length of time.
Word prediction is a feature that reduces keystrokes when words are selected from the
Figure 2-6 Four layouts of SofType on-screen keyboard
word list. SofType supports abbreviation expansion and word prediction to increase the performance. The macro feature of this text entry system allows user to type phrases and other commonly used strings of text and commands. Besides, in order to provide better contrast or make particular groups of characters more easily identifiable, SofType supports a means of changing the colors and fonts.
Table 2-1 compares the features of the four different on-screen keyboards mentioned above. Table 2-1 illustrates the most common on-screen keyboards supporting three different selection methods, including clicking selection method, scanning selection method and dwell selection method. Some on-screen keyboards provide several additional features to enhance the performance of the text entry for novice users. The three common solutions are voice feedback, word prediction, saving user’s configuration and customizing layout.
Table 2-1 Comparison the features of four on-screen keyboards
2.3 Related research of on-screen keyboard design
Numerous studies had investigated the use of on-screen keyboards that assisted persons with disabilities to access computers. Parts of those studies identified differences in the effects of interface design; other studies presented that particular input methods could enhance users’ performances.
2.3.1 Layout Patterns
The efficiency of the text entry depends on the suitability of control interface, which includes proper selection methods and keyboard layouts (Cook & Hussey, 2002). The standard computer keyboard is labeled with the QWERTY layout.
Although the QWERTY layout is applied to the most on-screen keyboards, however, it is not a proper user interface for people with physical impairments. The QWERTY keyboard design was made to have many adjacent letters to appear on the opposite sides of the keyboard to minimize mechanical jamming (Cooper, 1983). Because high frequency keys were placed at the far corners of the keyboard to provide the mechanical clearance to avoid key jamming, extreme travel of the fingers occurs. The QWERTY configuration requires full finger movement within their range of motion, possibly placing them at high risk of overuse problems (Struck, 1999). This design facilitates the frequent alternation of the left and right hand. The QWERTY keyboard layout is not an efficient design for several reasons. The drawbacks of the QWERTY
keyboard are in its two-handed design and its requirement of the full use of all ten fingers. Previous studies indicated that the letter arrangement with QWERTY has been demonstrated to be less efficient than other keyboard arrangements (Chubon &
Hester, 1988).
Besides the dominant QWERTY layout, many on-screen keyboards support various layouts. Most of the on-screen keyboards support a layout in alphabetical order. For novice users, the entry speed is determined mostly by the needs to search and find target keys rather than by the amount of motor movement. The keyboard layout in alphabetical order will be faster for novice users in the beginning.
To minimize finger movement on an on-screen keyboard, two factors must be taken into account. One factor is the transitional frequencies from one letter to another, According to Fitts’ law, the other factor is the distances between targets (Bravo, LeGare, Cook, & Hussey, 1993). Besides the QWERTY layout and the alphabetical layout, several studies support the alternative layouts to facilitate faster or more accurate use of text entry task.
Figure 2-7 Dvorak two-handed keyboard
A great number of different layout designs for keyboards have been produced since QWERTY, and the Dvorak keyboard is the most famous among them (Cassingham, 1986). The original design of Dvorak keyboard reduces the amount of motion required of text entry task by placing the most commonly used letters on the home row of the layout (as shown in Figure 2-7). Dvorak is much easier to learn than QWERTY, especially for new typists (Brooks, 2000). Dvorak argued that this layout design would improve typing speed and reduce finger travel. Previous research indicated that Dvorak keyboard provided better balance of both hand loading and finger loading (Yamada, 1980). Furthermore, the summary of the performance evaluation of Dvorak keyboard and QWERTY shows Dvorak keyboard is easier to learn, more accurate and less fatigue-inducing.
As shown in figure 2-8 and figure 2-9, the Dvorak one-handed keyboard layout was designed for typing with only the right hand or left hand. It is strategically designed so the keys pressed most often are placed nearest to the strongest fingers and
These features make the most frequently typed characters on a keyboard more accessible to people who have difficulties using the standard keyboard layout but have normal strength and movement in one hand. Letters of higher frequency are placed under the first finger of the hand, and lower frequency letters are placed away from the home row so they are typed with fingers that have less strength and mobility.
Figure 2-8 Dvorak left-handed keyboard
Figure 2-9 Dvorak right-handed keyboard
The FITALY soft keyboard is a commercial product designed to optimize text entry with the point and click selection method. The FITALY keyboard arranges keys in a square layout by optimizing the characters for minimal traveling time (as shown
in Figure 2-10). The principle of FITALY keyboard design included center placement of more frequently used keys, two double-sized space keys and the consideration of letters frequencies (Zhai, S., Hunter, M., & Smith, B.A., 2002).
Figure 2-10 The layout arrangement of FITALY on-screen keyboard
Figure 2-11 shows the Chubon keyboard layout, the layout of the Chubon keyboard arranges the keys of the most commonly used letters to be clustered in the center. A previous study has indicated that the Chubon keyboard required about 37 % less finger movement than the QWERTY keyboard (Anson, 1997).
Figure 2-11 The layout arrangement of Chubon on-screen keyboard
Fitts' law provides a criterion to measure the tapping time by giving the length
form a prediction for the upper bound of a user’s performance. MacKenzie and Zhang propose an on-screen keyboard with OPTI layout as shown in Figure 2-12 (MacKenzie & Zhang, 1999; Zhang, 1998). According to the calculations by MacKenzie and Zhang, the OPTI layout is theoretically 35% faster than QWERTY layout and 5% faster than FITALY layout. The error rate with OPTI is consistently slightly lower than with QWERTY.
Figure 2-12 The layout arrangement of OPTI text entry system
2.3.2 Enhancement of Performance
Besides the layout patterns, some specific features of an input device provide more efficiency by minimizing typing errors and maximizing speed. Many on-screen keyboards that support word prediction enhance the performance of text entry task.
Word prediction programs prompt the user with a list of likely word choices based on words previously typed. The idea of word prediction could reduce the number of keystrokes needed for individuals with motor disabilities by making text entry task
less energy-draining. However, word prediction in some cases will decrease the typing speed. One reason given for the failure of word prediction to accelerate typing is that the user must look away from text input task to scan the prediction list.
However, the results of a previous research (Anson, Moist, Przywara, Wells, Saylor,
& Maxime, 2006) show that the use of word prediction and word completion may assist on-screen keyboard users to improve typing speed for persons with severe motor disabilities. Previous study revealed that word prediction systems have been observed to reduce the number of keystrokes required by up to 60% (Newell, Arnott, Cairns, Ricketts & Gregor, 1995)
The FOCL (Fluctuating Optimal Character Layout) on-screen keyboard embeds nine currently used keys based on the previously types letters in the center of an alphabetical layout (as shown in Figure 2-13). Results with the FOCL keyboard were about 10 words per minute after 10 sessions of 15 minutes (Bellman & MacKenzie, 1998). However, the disadvantage of the FOCL on-screen keyboard is the increase of cognitive load to review the location of nine currently used keys.
Figure 2-13 The FOCL on-screen keyboard
2.3.3 The Design of Coded Text Entry System
The chorded keyboards have few keys than a standard keyboard. The user types by playing different chords to generate different characters. The chorded keyboards apply coded selection methods. The fingers do not need to travel very far when using a chorded keyboard thanks to its few keys. This can greatly reduce the strain and muscle fatigue. The chorded input methods are useful for people with one hand or people with limited arm range. Most of the coded selection methods are designed by hardware. It might be a good design to embed the chorded input methods to an on-screen keyboard.
Matias, MacKenzie and Buxton (1999) proposed the Half-QWERTY keyboard, a modified keyboard shown in Figure 2-14. The Half-QWERTY keyboard, which requires only one hand to type, is comprised of all the used keys on a QWERTY layout. When a key is pressed, the character in the upper left of the key is entered.
When a key press is preceded by holding down the space bar, the character in the
When a key press is preceded by holding down the space bar, the character in the