Michael C. Bartha

The Effect of Key Size of Touch Screen Virtual Keyboards on Productivity, Usability, and Typing Biomechanics

Objective: We investigated whether different virtual keyboard key sizes affected typing force exposures, muscle activity, wrist posture, comfort, and typing productivity. Background: Virtual keyboard use is increasing and the physical exposures associated with virtual keyboard key sizes are not well documented. Method: Typing forces, forearm/shoulder muscle activity, wrist posture, subjective comfort, and typing productivity were measured from 21 subjects while they were typing on four different virtual keyboards with square key sizes, which were 13, 16, 19, and 22 mm on each side with 2-mm between-key spacing. Results: The results showed that virtual keyboard key size had little effect on typing force, forearm muscle activity, and ulnar/radial deviation. However, the virtual keyboard with the 13-mm keys had a 15% slower typing speed (p < .0001), slightly higher static (10th percentile) shoulder muscle activity (2% maximum voluntary contractions, p = .01), slightly greater wrist extension in both hands (2° to 3°, p < .01), and the lowest subjective comfort and preference ratings (p < .1). Conclusions: The study findings indicate that virtual keyboards with a key size less than 16 mm may be too small for touch typing given the slower typing speed, higher static shoulder muscle activity, greater wrist extension, and lowest subjective preferences. Applications: We evaluated the effects of virtual keyboard key sizes on typing force exposures, muscle activity, comfort, and typing productivity.

Are there Differences in Force Exposures and Typing Productivity between Touchscreen and Conventional Keyboard

As the use of tablets is becoming increasingly prevalent, it is important to understand how using a touchscreen (virtual) keyboard affects typing forces, productivity and comfort. Thus, the objective of this study was to investigate whether there were differences in typing forces, typing productivity and users’ discomfort between virtual and conventional keyboards. A total of 19 subjects (10 males and 9 females) typed for 10 minutes on a virtual keyboard and two conventional keyboards. The results showed that virtual keyboard use resulted in lower typing forces (p < 0.0001), lower typing performance (p < 0.0001), and higher subjective discomfort at the hand/wrist and the neck/shoulder (p < 0.0001). The results indicate that using a virtual keyboard may not cause any detrimental effect on physical exposures, but may increase musculoskeletal discomfort on the upper extremities and neck/shoulder regions; therefore, appropriate interventions should be considered for the prolonged use of a virtual keyboard.

Shape Writing on Tablets: Better Performance or Better Experience?

Shape writing is a technology for text input that involves „drawing‟ the desired word with your finger or a stylus in one continuous motion on the virtual keyboard. Swype, initially introduced to smart phones, is a shape writing application that is advertised as being faster than traditional methods of keying on a virtual keyboard. This technology is relatively new to the market, and to date there is little available research on the performance of Swype on smart phones, and none on the even newer tablet devices, such as a Samsung Galaxy Tab. The present study investigated the performance (words per minute/average errors per word) and preference associated with the use of Swype for text input compared to keying on the virtual keyboard. The effect of keyboard sizes within landscape and portrait orientations was also examined. In the current implementation, the keying method did not have the benefit of a prediction algorithm, therefore prediction was turned off for Swype condition as well. No significant difference was found in typing speed between the two input methods, however, an effect of keyboard viewing orientation on typing speed was found. For average errors per word, the only significant effect was an interaction between input method and keyboard viewing orientation. Additionally, Swype was rated significantly better than keying on four out of five preference measures. Findings show that despite Swype not operating at its fullest ability, it performs just as well as keying and provides a better experience for users.

A Field Observation of Display Placement Requirements for Presbyopic and Prepresbyopic Computer Users

User-selected display placement for young computer users (prepresbyopes) and older computer users with presbyopia, wearing multifocal lens correction, has been observed in field settings, but not while both groups used the same display size or illumination technology. A field study was conducted to examine placement of an 18.5-inch, widescreen LCD display for prepresbyopes and presbyopes using multifocal lens correction. Both groups viewed the 18.5“ display for four days as they performed their usual computer tasks at their workstations. Multifocal wearers selected a display height that was lower than computer users who did not have presbyopia. As a result the eye-to-screen angle for presbyopes was significantly lower than prepresbyopes. The findings potentially affect proper design and selection of adjustable display supports. Measures of gross body posture and text size were also collected. Multifocal wearers did not choose seated postures different from prepresbyopes. Additionally, the majority of both groups viewed text at arc angles smaller than ANSI/HFES 100–2007 and ISO 9241–3 recommendations.

The effects of touch screen virtual keyboard key sizes on typing performance, typing biomechanics and muscle activity

The goal of the present study was to determine whether different touch screen virtual keyboard key sizes affected typing productivity, typing forces, and muscle activity. In a repeated-measures laboratory experiment with 21 subjects, typing speed, accuracy, muscle activity, and typing forces were measured and compared between four different key sizes: 13x13, 16x16, 19x19, and 22x22 mm. The results showed that 13 mm keyboard had a 15% slower typing speed (p < 0.0001) and slightly higher static (10th %tile) shoulder muscle activity (2%, p = 0.01) as compared to the other keyboards with larger keys. The slower typing speed and slightly higher shoulder muscle activity indicated that 13 mm keyboard may be less optimal for touch typing compared to the larger key sizes.

Low Profile Keyboard Design The Effect of Physical Key Characteristics On Typing Productivity and User Preference

The growing usage of tablets and the introduction of ultrabooks have increased consumer demands for smaller, lighter, sleeker, and more mobile devices. With computing technologies gravitating towards thinner designs, there is increased pressure to reduce key travel in order to accommodate the reduced thickness. It is important to understand how reductions in key travel may affect users’ performance and preferences. The main goal of this study was to examine how physical key characteristics affect user performance and preference on various computer keyboards. Four keyboards varying in key travel distances from 0.0 mm to 2.0 mm were compared. Participants completed a 7-minute typing task on each of the four keyboards. Typing performance (speed and accuracy) was collected for each of the keyboards. The results showed that words per minute were higher with the 1.6 mm and 2.0 mm keyboards and lower with the 0.4 mm and 0.0 mm keyboards. The 0.0 mm keyboard had a lower accuracy than the other three keyboards. Performance and usability ratings were significantly lower for the 0.0 mm keyboard compared with the other keyboards. Overall, both subjective and objective measures of performance and usability showed that the1.6 mm keyboard was preferred.

Examining 3-D Technologies in Laptop Displays

As 3-D content migrates to the laptop, it is important to understand if customers can perceive quality differences between the 3-D technologies and to know if they feel any discomfort with close-up viewing of 3-D displays. In this study, we compared the quality and viewing comfort of active, passive, and autostereoscopic (glasses-free) 3-D displays. We found that participants were able to discern differences in 3-D quality and comfort on laptop computer displays in realistic viewing conditions within a short period. Although the active and passive displays were comparable, the autostereoscopic display was rated lower in quality and viewing comfort.

The Effects of Virtual Keyboard Key Sizes on Typing Productivity and Physical Exposures

With mobile devices including tablet PCs, gravitating towards smaller sizes, the keyboard key sizes on these devices often have to be smaller than recommended key sizes and spacing (18 to 20 mm) for notebook and desktop keyboards. Currently, there is limited research into how key sizes can affect typing proficiency and physical exposures during virtual keyboard use. Therefore, the present study investigated how different virtual keyboard key sizes affected muscle activity, wrist posture, and typing productivity. A total of 21 subjects (12 males and 9 females) participated in a repeated-measures laboratory experiment where typing speed, accuracy, muscle activity, wrist posture, and subjective discomfort were compared between four different virtual keyboards with key sizes (width x height) of 13x13, 16x16, 19x19, and 22x22 mm with a 2-mm gutter surrounding each key. The results showed that the keyboard with the 13x13 mm keys (15 mm center-to-center key spacing) had a 15% slower typing speed (p < 0.0001), higher static (10th %tile) shoulder muscle activity (2% MVC, p = 0.01), and greater wrist extension in both hands (2° - 3°, p’s < 0.01). The study findings indicate that 13x13 mm key size may not be optimal for touch typing on a virtual keyboard.

Field observations of display placement requirements and character size for presbyopic and prepresbyopic computer users

BACKGROUND Computer users continue to report eye and upper body discomfort even as workstation flexibility has improved. Research shows a relationship between character size, viewing distance, and reading performance. Few reports exist regarding text height viewed under normal office work conditions and eye discomfort. OBJECTIVE This paper reports self-selected computer display placement, text characteristics, and subjective comfort for older and younger computer workers under real-world conditions. METHODS Computer workers were provided with monitors and adjustable display support(s). In Study 1, older workers wearing progressive-addition lenses (PALs) were observed. In study 2, older workers wearing multifocal lenses and younger workers were observed. RESULTS Workers wearing PALs experienced less eye and body discomfort with adjustable displays, and less eye and neck discomfort for text visual angles near or greater than ergonomic recommendations. Older workers wearing multifocal correction positioned displays much lower than younger workers. In general, computer users did not adjust character size to ensure that fovial images of text fell within the recommended range. CONCLUSIONS Ergonomic display placement recommendations should be different for computer users wearing multifocal correction for presbyopia. Ergonomic training should emphasize adjusting text size for user comfort.

Neck Biomechanics and Multiple Wide Computer Displays

Computer workstations are increasingly being fitted with multiple large displays. Display placement influences head posture and neck symptoms but the effects of multiple displays are not well known. This study evaluated the placement of two wide displays over a large range of heights and distances. Twenty participants performed internet search tasks with the search window at thirty-six positions, defined by three distances from the eyes (50 to 86 cm), three gaze angles (0 to 28° below the eye horizon), and four lateral distances from the mid-sagittal plane (13 and 32 cm to the left and to the right). Motion capture equipment tracked head and neck postures and simulation software calculated muscular capacities. Regression analyses demonstrated significant (p < 0.001) effects of gaze angle on neck flexion, lateral angle on neck rotation, and the interaction of gaze angle and lateral angle on neck lateral flexion. The moment generating capacities of the trapezius and splenius muscles, and the self-selected display positions, suggest that increases in wide displays field-of-view should be biased vertically (upward).