Theoretical upper and lower bounds on typing speed using a stylus and a soft keyboard

Abstract

A theoretical model is presented to predict upper-and lower-bound text-entry rates using a stylus to tap on a soft QWERTY keyboard. The model is based on the Hick-Hyman law for choice reaction time, Fitts law for rapid aimed movements, and linguistic tables for the relative frequencies of letter-pairs, or digrams, in common English. The model's importance lies not only in the predictions provided, but in its characterization of text-entry tasks using keyboards. Whereas previous studies only use frequency probabilities of the 26 × 26 digrams in the Roman alphabet, our model accommodates the space har—the most common character in typing tasks. Using a very large linguistic table that decomposes digrams by position-within-words, we established start-of-word (space-letter) and end-of-word (letter-space) probabilities and worked from a 27 × 27 digram table. The model predicts a typing rate of 8.9wpm for novices unfamiliar with the QWERTY keyboard, and 30.1wpm for experts. Comparisons are drawn with empirical studies using a stylus and other forms of text entry.     

Improving touchscreen keyboards: design issues and a comparison with other devices

The study explored touchscreen keyboards using high precision touch-screen strategies. Phase one evaluated three possible monitor positions: 30°, 45°, and 75° from horizontal. Results indicate that the 75° angle, approximately the standard monitor position, resulted in more fatigue and lower preference ratings. Phase two collected touch bias and key size data for the 30° angle. Subjects consistently touched below targets, and touched to the left of targets on either side of the screen. Using these data, a touchscreen keyboard was designed. Phase three compared this keyboard with a mouse-activated keyboard, and the standard QWERTY keyboard for typing relatively short strings of 6,19, and 44 characters. Results indicate that users can type approximately 25 words/minute (wpm) with the touchscreen keyboard, compared to 17 wpm using the mouse, and 58 wpm when using the keyboard. Possible improvements to touchscreen keyboards are suggested.     

An empirical investigation of the novice experience with soft keyboards

An experiment with 12 participants tested text entry rates on two sizes of soft keyboards with either a Qwerty layout or a layout presenting a randomized letter arrangement after each tap. The randomized layout simulated the novice experience by requiring users to visually scan the layout for each tap to find the intended letter. Rates for the Qwerty layouts were about 20 wpm with no significant difference between the large and small size. Rates for both sizes of the randomized layouts were very low, about 5.4 wpm. This is the expected walk-up text entry rate with a soft keyboard bearing an unfamiliar layout. This empirical result allows us to reject a previous model of novice interaction that used Fitts' law for stylus movement and the Hick-Hyman law for visual scan time.     

Enhancing typing performance of older adults on tablets

Touch screen interfaces are increasingly more popular. However, they lack haptic feedback, making it harder to perform certain tasks, such as text entry, where users have to constantly select one of many small targets. This problem particularly affects older users, whose deteriorating physical and cognitive conditions, combined with their unfamiliarity with technology, can discourage them from using touch devices. The goal of this work was to thoroughly understand older adults touch typing behavior, in order to develop text-entry solutions more appropriate to their needs, which will enhance their typing performance. On a first phase, a baseline QWERTY keyboard and five different variants were developed that mostly used a text prediction algorithm to suggest the most probable keys or words. These keyboards were evaluated on a baseline study with 20 younger adults in order to find the most promising ones, which were then used in a study with 20 older adults. The older adults study revealed more about their typing behavior and therefore created four new variants to be used in a simulation study. Results show that visual changes should be kept to a minimum; touch points should be shifted upward and to the opposite side of the hand used to type; single touch keyboards perform better than multi-touch; and omitting keys below a certain time threshold minimizes accidental insertions.     

An empirical investigation of the novice experience with soft keyboards

An experiment with 12 participants tested text entry rates on two sizes of soft keyboards with either a Qwerty layout or a layout presenting a randomized letter arrangement after each tap. The randomized layout simulated the novice experience by requiring users to visually scan the layout for each tap to find the intended letter. Rates for the Qwerty layouts were about 20 wpm with no significant difference between the large and small size. Rates for both sizes of the randomized layouts were very low, about 5.4 wpm. This is the expected walk-up text entry rate with a soft keyboard bearing an unfamiliar layout. This empirical result allows us to reject a previous model of novice interaction that used Fitts' law for stylus movement and the Hick-Hyman law for visual scan time.     

Mobile text-entry and visual demands: reusing and optimizing current solutions

Mobile devices are increasingly used for text-entry in contexts where visual attention is fragmented and graphical information is inadequate, yet the current solutions to typing on virtual keyboards make it a visually demanding task. This work looks at assistive technologies and interface attributes as tools to ease the task. Two within-subject experiments were performed with 23 and 17 participants, respectively. The first experiment aimed to understand how walking affected text-entry performance and additionally to assess how effective assistive technologies can be in mobile contexts. In the second experiment, adaptive keyboards featuring character prediction and pre-attentive attributes to ease visual demands of text-entry interfaces were developed and evaluated. It has been found that both text-input speed and overall quality are affected in mobile situations. Contrary to the expectations, assistive technologies proved ineffective with visual feedback. The second experiment showed that pre-attentive attributes do not affect users’ performance in task-entry tasks, even though a 3.3–4.3 % decrease in error rates was measured. It was found that users reduce walking speed to compensate for challenges placed by mobile text-entry. Caution should be exercised when transferring assistive technologies to mobile contexts, since they need adaptations to address mobile users’ needs. Also, while pre-attentive attributes seemingly have no effect on experienced QWERTY typists’ performance, they showed promise for both novice users and typists in attention-demanding contexts.     

Adaptive blind interaction technique for touchscreens

This paper describes the development of a new technique for touchscreen interaction, based on a single gesture-driven adaptive software button. The button is intended to substitute the software keyboard, and provides text-entry functionality. Input is accomplished through recognition of finger gestures that is comprised of movement towards the eight basic directions in any position. The target user group of such an interaction technique is primarily blind people who could benefit significantly. The adaptability of the button provides complementary help and follows the style of interaction in a natural way. The analysis of the results, collected from twelve blindfolded subjects, revealed an encouraging tendency. During blind manipulation on touch screen, three of the subjects achieved a maximal typing speed of about 12 wpm after five trials. This suggests that the technique developed is reliable and robust enough to be possibly applied to diverse application platforms, including personal device assistants.     

Data Entry for Mobile Devices Using Soft Keyboards: Understanding the Effects of Keyboard Size and User Tasks

As mobile, handheld computing devices become more common and are used for an ever-increasing variety of tasks, new mechanisms for data entry must be investigated. Personal digital assistants often provide a small stylus-activated soft keyboard, as do some mobile phones that include touch screens. However, there is little data regarding the importance of keyboard size or the users' tasks, the effectiveness of these keyboards, or user reactions to these keyboards. In this article, an experiment designed to investigate these issues in the context of a palm-style QWERTY keyboard is described. In this study, 30 novices completed 6 realistic tasks using either a small, medium, or large soft keyboard. The results not only confirm that keyboard size does not affect data entry rates but that making the keyboard smaller does not increase error rates or negatively impact preference ratings. However, tasks that required users to switch between the alphabetic keyboard and the numeric keyboard do result in significantly slower data entry rates. A model that accurately predicts the time required to enter predefined text is presented, and directions for future research are discussed.     

Multilingual Touchscreen Keyboard Design and Optimization

A keyboard design, once adopted, tends to have a longlasting and worldwide impact on daily user experience. There is a substantial body of research on touch-screen stylus keyboard optimization. Most of it has focused on English only. Applying rigorous mathematical optimization methods and addressing diacritic character design issues, this article expands this body of work to French, Spanish, German, and Chinese. More important and counter to the intuition that optimization by nature is necessarily specific to each language, this article demonstrates that it is possible to find common layouts that are highly optimized across multiple languages for stylus (or single finger) typing. We first obtained a layout that is highly optimized for both English and French input. We then obtained a layout that is optimized for English, French, Spanish, German, and Chinese pinyin simultaneously, reducing its stylus travel distance to about half of QWERTY's for all of the five languages. In comparison to QWERTY's 3.31, 3.51, 3.7, 3.26, and 3.85 keys of movement for English, French, Spanish, German, and Chinese, respectively, the optimized multilingual layout has an average travel distance of 1.88, 1.86, 1.91, 1.77, and 1.68 keys, correspondingly. Applying Fitts's law with parameters validated by a word tapping experiment, we show that these multilingual keyboards also significantly reduce text input time for multiple languages over the standard QWERTY for experienced users. In comparison to layouts individually optimized for each language, which are also obtained in this article, simultaneously optimizing for multiple languages caused only a minor performance degradation for each language. This surprising result could help to reduce the burden of multilingual users having to switch and learn new layouts for different languages. In addition, we also present and analyze multiple ways of incorporating diacritic characters on multilingual keyboards. Taken together, the present work provides a quantitative foundation for the understanding and designing of multilingual touch-screen keyboards.     

Top-down learning strategies: can they facilitate stylus keyboard learning?

Learning a new stylus keyboard layout is time-consuming yet potentially rewarding, as optimized virtual keyboards can substantially increase performance for expert users. This paper explores whether the learning curve can be accelerated using top-down learning strategies. In an experiment, one group of participants learned a stylus keyboard layout with top-down methods, such as visuo-spatial grouping of letters and mnemonic techniques, to build familiarity with a stylus keyboard. The other (control) group learned the keyboard by typing sentences. The top-down learning group liked the stylus keyboard better and perceived it to be more effective than the control group. They also had better memory recall performance. Typing performance after the top-down learning process was faster than the initial performance of the control group, but not different from the performance of the control group after they had spent an equivalent amount of time typing. Therefore, top-down learning strategies improved the explicit recall as expected, but the improved memory of the keyboard did not result in quicker typing speeds. These results suggest that quicker acquisition of declarative knowledge does not improve the acquisition speed of procedural knowledge, even during the initial cognitive stage of the virtual keyboard learning. They also suggest that top-down learning strategies can motivate users to learn a new keyboard more than repetitive rehearsal, without any loss in typing performance.     

Text Input on a Smartwatch QWERTY Keyboard: Tap vs. Trace

This study examines text input performance on a smartwatch using tap and trace input methods on a standard QWERTY keyboard (Swype^TM). Participants were either experts or novices to the tracing technique on their smartphone. No users had experience typing on a smartwatch. Participants were able to type at speeds comparable to, or exceeding, those reported in the literature for smartphones and small screen devices. Both novices and tracing experts typed faster overall using the trace input method than the tap method and experts typed the fastest using trace (37 WPM). Word error rates were also comparable to those reported for smartphone text input. These results suggest that using a standard QWERTY keyboard that allows both tap and trace for text input is a viable option on a smartwatch.     

Productivity prediction by extrapolation: Using workload memory as a predictor of target performance

In order to assess if productivity based on extrapolated data is a good predictor of longer texts, an experimental study was conducted. Two full-sized text input devices for touch typing and two miniaturized for tapping were used, all featuing QWERTY layout, in a repeated measurement design. Twenty subjects were exposed to both a task within the limit of working memory (nine words) and four running memory tasks (approx. 275 words). For miniaturized tapping keyboards, extrapolated data significantly underestimated both entry speed (uncorrected wpm, up to 17%) and character error rate (up to 61%) whereas it significantly overestimated ratio of correct words (up to 62%) of running memory tasks. Further, error-corrected entry speed was significantly overestimated up to a factor of 2.7. Results based on extrapolated productivity metrics must therefore be interpreted with caution. Running memory tasks with text length of more than 32 words is needed to assess productivity of text input devices if tapping is used.     

英文输入用键盘布局的改进

现有英文输入用键盘的字母区布局基本上沿用QWERTY英文机械打字机布局，在英文输入中存在输入困难、速度慢、输入易疲劳等缺点。提出了一种改进的键盘布局，该布局结合了英文26个字母的出现频率和键盘字母区各键位的使用难易程度并为最经常使用的字母对的连续输入做了优化，使用改进后的键盘布局可以在获得最快的英文输入速度的同时大幅度地提高输入时的舒适度，降低手指的疲劳度。     

Bimanual text entry using game controllers: Relying on users’ spatial familiarity with QWERTY

A strategy for entering text using two-handed game controllers with two analogue joysticks is proposed where the QWERTY keyboard layout is used as a spatial mnemonic. The technique is inspired by two-finger QWERTY typing where the fingers are represented by the two joysticks. Characters are organized into a QWERTY layout with the joystick resting position conceptually located where the index fingers are in touch position. The user moves the relevant joystick in the direction of the desired character. The technique is easy to learn for users already familiar with QWERTY two-finger typing or touch-typing. Furthermore, text can potentially be entered with limited visual feedback, and the bimanual nature of the approach implies a potential for high input speed as the operation of each hand can be overlapped. The technique can be realized with commonly available off-the-shelf hardware and it is especially applicable to online gamers communicating textually. Experimental evaluations show that text can be entered at a mean rate of 6.75 words per minute with less than one hour of practice.     

Productivity prediction by extrapolation: using workload memory as a predictor of target performance

In order to assess if productivity based on extrapolated data is a good predictor of longer texts, an experimental study was conducted. Two full-sized text input devices for touch typing and two miniaturized for tapping were used, all featuing QWERTY layout, in a repeated measurement design. Twenty subjects were exposed to both a task within the limit of working memory (nine words) and four running memory tasks (approx. 275 words). For miniaturized tapping keyboards, extrapolated data significantly underestimated both entry speed (uncorrected wpm, up to 17%) and character error rate (up to 61%) whereas it significantly overestimated ratio of correct words (up to 62%) of running memory tasks. Further, error-corrected entry speed was significantly overestimated up to a factor of 2.7. Results based on extrapolated productivity metrics must therefore be interpreted with caution. Running memory tasks with text length of more than 32 words is needed to assess productivity of text input devices if tapping is used.     

Wrist postures while keyboarding: effects of a negative slope keyboard system and full motion forearm supports

Abstract

Video-motion analysis was used to analyse hand/wrist posture for subjects typing at a 101-key QWERTY keyboard on a 68 cm high worksurface. Three conditions were tested: subjects typed at the keyboard without arm support, subjects typed with adjustable full motion forearm supports, and subjects typed with an adjustable negative slope keyboard support system. The average declination of the negative slope keyboard support chosen by subjects was 12° below horizontal, which flattened the angle of the key tops. Ulnar deviation was comparable in all conditions and averaged 13° for the right hand and 15° for the left hand. Full motion forearm supports did not significantly affect any postural measures. Dorsal wrist extension averaged 13° when typing with or without the full motion forearm supports, but this was reduced to an average — 1° with the use of the negative slope keyboard support system. Subjects chose to sit at a distance of 79 cm from the computer screen when using the negative slope keyboard system compared with 69 cm without this.     

基于触摸显示屏的手势输入字符方法研究

针对触摸显示屏的操作特点,利用简单通用手势——滑动和点击,提出了两种触摸手势输入字符方法。第一种是基于T9键盘的改进输入方法,第二种是基于全键盘的改进输入方法。这两种输入方法节省屏幕使用空间,使用户更易学习的同时降低了误输入机率。     

The role of visual search in the design of effective soft keyboards

As portable, handheld computing devices become more common, alternatives to traditional keyboards must be explored. These alternatives must be compact, lightweight and sufficiently efficient to support the users' tasks. One alternative is the use of small physical keyboards or soft keyboards presented on touch-sensitive surfaces. Many alternative layouts have been explored, including the QWERTY, Dvorak, telephone and various alphabetic organizations. Soukoreff and MacKenzie proposed a model to predict typing times for alternative layouts, but have experienced limited success matching their predictions to observed performance. This paper proposes a revision of the visual search component of their model that considers the familiarity of the organization and the number of letters represented by each key. Results are reported of an experiment that supports the claim that both familiarity and the number of letters per key must be considered when predicting visual search times for alternative keyboard layouts.     

Effects of negatively sloped keyboard wedges on risk factors for upper extremity work-related musculoskeletal disorders and user performance

Several changes to computer peripherals have been developed to reduce exposure to identified risk factors for musculoskeletal injury, notably in keyboard designs. Negative keyboard angles and their resulting effects on objective physiological measures, subjective measures and performance have been studied, although few angles have been investigated despite the benefits associated with their use. The objective of this study was to quantify the effects of negative keyboard angles on forearm muscle activity, wrist posture, key strike force, perceived discomfort and performance and to identify a negative keyboard angle or range of keyboard angles that minimizes exposure to risk factors for hand/wrist injuries. Ten experienced typists (four males and six females) participated in a laboratory study to compare keyboard angles ranging from 0 degrees to -30 degrees , at 10 degrees increments, and a keyboard with a 7 degrees slope, using a wedge designed for use with standard QWERTY keyboards. Repeatability of exposures was examined by requiring participants to complete two test sessions 1 week apart. Dependent variable data were collected during 10 min basic data entry tasks. Wrist posture data favoured negative keyboard angles of 0 degrees (horizontal) or greater, compared to a positive keyboard angle of 7 degrees , especially for the flexion/extension direction. In general, the percentage of wrist movements within a neutral zone and the percentages of wrist movements within +/-5 degrees and +/-10 degrees increased as keyboard angle became more negative. Electromyography results were mixed, with some variables supporting negative keyboard angles whilst other results favoured the standard keyboard configuration. Net typing speed supported the -10 degrees keyboard angle, whilst other negative typing angles were comparable, if not better than, with the standard keyboard. Therefore, angles ranging from 0 degrees to -30 degrees in general provide significant reductions in exposure to deviated wrist postures and muscle activity and comparable performance.     

Effects of negatively sloped keyboard wedges on risk factors for upper extremity work-related musculoskeletal disorders and user performance

Several changes to computer peripherals have been developed to reduce exposure to identified risk factors for musculoskeletal injury, notably in keyboard designs. Negative keyboard angles and their resulting effects on objective physiological measures, subjective measures and performance have been studied, although few angles have been investigated despite the benefits associated with their use. The objective of this study was to quantify the effects of negative keyboard angles on forearm muscle activity, wrist posture, key strike force, perceived discomfort and performance and to identify a negative keyboard angle or range of keyboard angles that minimizes exposure to risk factors for hand/wrist injuries. Ten experienced typists (four males and six females) participated in a laboratory study to compare keyboard angles ranging from 0° to ?30°, at 10° increments, and a keyboard with a 7° slope, using a wedge designed for use with standard QWERTY keyboards. Repeatability of exposures was examined by requiring participants to complete two test sessions 1 week apart. Dependent variable data were collected during 10 min basic data entry tasks. Wrist posture data favoured negative keyboard angles of 0° (horizontal) or greater, compared to a positive keyboard angle of 7°, especially for the flexion/extension direction. In general, the percentage of wrist movements within a neutral zone and the percentages of wrist movements within ±5° and ±10° increased as keyboard angle became more negative. Electromyography results were mixed, with some variables supporting negative keyboard angles whilst other results favoured the standard keyboard configuration. Net typing speed supported the ?10° keyboard angle, whilst other negative typing angles were comparable, if not better than, with the standard keyboard. Therefore, angles ranging from 0° to ?30° in general provide significant reductions in exposure to deviated wrist postures and muscle activity and comparable performance.