This research is supported by the Tsinghua University Initiative Scientific Research Program (Ergonomic design of curved keyboard on smart devices). The authors appreciate Tianyu Liu for his kind suggestions and coding assistance on figures.

The study was conducted in accordance with the ethical principle and was approved by the Ethics Committee of Tsinghua University. Figure 1 shows the process of evaluating the keyboard design of smartphones.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61796/61796fig01.jpg" /> 
Figure 1: General process of conducting a keyboard experiment and evaluating the keyboard design. <a href="https://www.jo...

<ol>
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The authors declared no financial disclosure or conflicts of interest.

In this study, based on the development of screen technology, we presented a summarized and general protocol of keyboard design evaluation to assess the keyboard design systematically and precisely. Existing indicators and methods from previous studies, pairs matched by English characters, and transition time between two keys are integrated and modified to generate an effective protocol.
Several critical points need to be noticed in this protocol. The selection of variables and indicators is e...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61796">An Assessment Method and Toolkit to Evaluate Keyboard Design on Smartphones</a>. The Authors section was&#160;updated.
Yincheng Wang1 
Ke Wang1 
Yuqi Huang1 
Di Wu2 
Jian Wu3 
Jibo He4,1 
1Department of Psychology, School of Social Sciences, Tsinghua University 
2Department of Computer Science, Beijing Normal University 
3Haier Innovation Design Center, Haier Company 
4Key Laboratory of Emotion and Mental Health in Chongqing, User Experience and Human-computer Interaction Technology Institute, Chongqing University of Arts and Sciences
to:
Yincheng Wang1 
Ke Wang1 
Yuqi Huang1 
Di Wu2 
Jian Wu3 
Jibo He1 
1Department of Psychology, School of Social Sciences, Tsinghua University 
2Department of Computer Science, Beijing Normal University 
3Haier Innovation Design Center, Haier Company

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61796">An Assessment Method and Toolkit to Evaluate Keyboard Design on Smartphones</a>. The Authors section was&#160;updated.

Erratum: An Assessment Method and Toolkit to Evaluate Keyboard Design on Smartphones

Keyboard input is the mainstream method of the human-smartphone interaction1,2, and with the penetration of smartphones, keyboard input gets billions of users. In 2019, the global smartphone penetration rate had reached 41.5%3, while the United States, with the highest penetration, had come up to 79.1%4. Up to the first quarter of 2020, the Sogou mobile keyboard had about 480 million daily active users5. Up to May 6, 2020, the Google Gboard had been downloaded more than 1 billion times6.
Unsatisfactory keyboard input experience increases with the enlargement of the phone screen. Although the enlarged screen aimed to improve the viewing experience, it has changed the gravity, size, and weight of smartphones, causing users to change holding posture repeatedly to reach remote areas (e.g., button A and Q for right-handed users), thus leading to input inefficiency. The stretch of muscle may cause users to suffer from musculoskeletal disorders, hand pains, and different types of disease (e.g., carpal tunnel syndrome, thumb osteoarthritis, and thumb tenosynovitis7,8,9,10). Users who prefer one-handed usage are under worse conditions11,12.
Therefore, the evaluation and optimization of keyboard design have become hot topics of psychological, technical, and ergonomic research. Variable keyboard designs and concepts have constantly been proposed by input method editor (IME) companies and researchers to optimize input experience and efficiency, including layout-changed and character-reordered keyboards: Microsoft WordFlow Keyboard13, Functional Button Area in Glory of Kings14, IJQWERTY15, and Quasi-QWERTY16.
Existing evaluation methods of keyboard design vary from researcher to researcher except for several highly accepted indicators, and more accurate indicators are proposed. However, with a variety of indicators, there is not a summarized and systematic protocol provided to demonstrate the process of evaluating and analyzing the keyboard design. Fitts&#8217; Law17 and its extended version FFitts&#160;Law18, which described human-computer interaction, were widely adopted to evaluate keyboard performance19,20,21,22. Moreover, the functional area of the thumb was proposed to improve keyboard design, and it described a curved motion area for the thumb to comfortably complete the input task23. Based on these theories, indicators including word per minute, word error rate, and subjective feedback (perceived usability, perceived performance, perceived speed, subjective workload, perceived exertion and pain, and intent to use, etc.), which were highly adopted, were partially used in previous studies24,25,26,27,28,29 except for modeling and simulation methods. In addition, the fitted ellipse of touchpoints on each button and its offset30,31 were used in recent years to investigate the accurate performance of inputting events. Also, the galvanic skin response, heart rate, electromyographic activity, hand gesture, and body movement32,33,34,35 were adopted to directly or indirectly evaluate muscle fatigue, comfort, and satisfaction of the users. However, these various methods lack reflection on the appropriateness of the indicators used, and a novice researcher may be confused to select the appropriate indicators for his or her research.
The research about keyboard design is also easy to be conducted, operated, and analyzed. With the boom of screen technology, more behavioral data could be easily collected to evaluate the keyboard design in-depth (e.g., the transition time between two keys and the coordinate data of each touchpoint). Based on the mentioned data, researchers could precisely explore the details of keyboard design and analyze its disadvantages and advantages. When compared with other human-computer interaction research, the research of keyboard design on portable smartphones also has high application value for its vast user base with no expensive equipment, complicated materials, or huge laboratory space needed. The questionnaires, scales, and Python script about the research are open-source and easy to access.
The purpose of this research is to summarize the previous methods to demonstrate a systematic, precise, and general protocol to evaluate and analyze the keyboard design on smartphones. The exemplar experiment and results aim to show whether the curved QWERTY keyboard with size-adjustable buttons could optimize the input experience of one-handed input on a 5-inch smartphone when compared with traditional QWERTY keyboard and share the visualization method and Python script of data analysis.

<table>
	<tbody>
		<tr>
			<td>Changxiang 6S smartphone</td>
			<td>Huawei</td>
			<td></td>
			<td>Smartphone used in the examplar study</td>
		</tr>
		<tr>
			<td>Curved QWERTY keyboard software</td>
			<td>Tsinghua University</td>
			<td></td>
			<td>Developed by authors</td>
		</tr>
		<tr>
			<td>SPSS software</td>
			<td>IBM</td>
			<td></td>
			<td>Data analysis software</td>
		</tr>
		<tr>
			<td>G*Power software</td>
			<td>Heinrich-Heine-Universit&#228;t D&#252;sseldorf</td>
			<td></td>
			<td>Sample size calculation</td>
		</tr>
		<tr>
			<td>E4 portable wireless wristband</td>
			<td>Empatica</td>
			<td></td>
			<td>Recording galvanic skin response and heart rate</td>
		</tr>
		<tr>
			<td>Arqus</td>
			<td>Qualysis</td>
			<td></td>
			<td>Motion capture camera platform</td>
		</tr>
		<tr>
			<td>Passive marker</td>
			<td>Qualysis</td>
			<td></td>
			<td>Appropriate sizes: 2.5 mm, 4 mm, and 6.5 mm</td>
		</tr>
		<tr>
			<td>Trigno sEMG</td>
			<td>Delsys</td>
			<td></td>
			<td>Recording electromyographic activity</td>
		</tr>
		<tr>
			<td>Visual Studio Code</td>
			<td>Microsoft</td>
			<td></td>
			<td>Python editor</td>
		</tr>
	</tbody>
</table>

an assessment method and toolkit to evaluate keyboard design on smartphones

Keyboard input has played an essential role in human-computer interaction with a vast user base, and the keyboard design has always been one of the fundamental objects of studies on smart devices. With the development of screen technology, more precise data and indicators could be collected by smartphones to in-depth evaluate the keyboard design. The enlargement of the phone screen has led to unsatisfactory input experience and finger pain, especially for one-handed input. The input efficiency and comfort have attracted the attention of researchers and designers, and the curved keyboard with size-adjustable buttons, which roughly accorded with the physiological structure of thumbs, was proposed to optimize the one-handed usage on large-screen smartphones. However, its real effects remained ambiguous. Therefore, this protocol demonstrated a general and summarized method to evaluate the effect of curved QWERTY keyboard design on a 5-inch smartphone through a self-developed software with detailed variables, including objective behavioral data, subjective feedback, and the coordinate data of each touchpoint. There is sufficient existing literature on evaluating virtual keyboards; however, only a few of them systematically summarized and took reflection on the evaluation methods and processes. Therefore, this protocol fills in the gap and presents a process and method of the systematic evaluation of keyboard design with available codes for analysis and visualization.&#160;It needs no additional or expensive equipment&#160;and is easy to conduct and operate. In addition, the protocol also helps to get potential reasons for the disadvantages of the design and enlightens the optimization of designs. In conclusion, this protocol with the open-source resources could not only be an in-class demonstrative experiment to inspire the novice to start their studies but also contributes to improving the user experience and the revenue of input method editor companies.

The representative study is mainly following the mentioned protocol. The study adopts a 2 (Keyboard layout: Curved QWERTY vs. Traditional QWERTY) &#215; 2 (Button size: large, 6.3 mm &#215; 9 mm vs. small, 4.9 mm &#215; 7 mm) within-subject design to evaluate whether the curved QWERTY could improve the input efficiency and comfort when compared with the traditional QWERTY in different sizes of buttons by the character pair input task through our self-developed software (Figure 3). This study...

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An Assessment Method and Toolkit to Evaluate Keyboard Design on Smartphones

The presented protocol integrates various evaluation methods and demonstrates a method to evaluate the keyboard design on smartphones. Pairs matched by English characters are proposed as the input material, and the transition time between two keys is used as the dependent variable.

Keyboard input has played an essential role in human-computer interaction with a vast user base, and the keyboard design has always been one of the ...

This open source protocol and toolkit could inspire the novice to start their studies in keyboard designs, optimize the user experience, and improve the revenue of input method at the companies. This protocol provides a systematic method to evaluate the keyboard design more precisely on smartphones. Various highly accepted indicators, and the new special indicators are involved in this protocol.A novice researcher may be confused about choosing appropriate evaluating indicators, and experimental programming. We provide subjective indicators, objective indicators, and Python script to reference. Demonstrating the procedure will be Yincheng Wang and Ke Wang, students from my laboratory.Begin by reading the consent form to the participant regarding the experimental procedure, and their discretion for participation, including the experiment procedure task, and whether they will encounter any mental or physical injuries. If the participant agrees to participate, ask them to sign the informed consent form. Measure the hand size of every participant to eliminate the effect of hand size difference, and to provide repeatable data for future research.Collect demographic data, such as age, gender, precise input experience, and occupation of the participants. Disinfect all devices and clean the body parts of the participant that will touch the devices. Ask participants to wash their hands and clean their smartphone screens.Ask the participants to wear portable wireless physiological detectors, or a motion capture system. Then ask them to put the portable wireless physiological detection wristband on their non-dominant hand to record a galvanic skin response, and heart rate, without noise interference. To collect precise body and finger movement place passive markers of the motion capture system on the fingernails, the proximal phalanx of the finger, cervical vertebrae from C3 to C5, and arm.Stick wireless electrodes to the skin of the arms and forearms to detect the electromyographic activity. Then calibrate all devices. Allow the participant to complete the training task, which is used to improve their familiarity with the input tasks and keyboards.Only allow participants whose accuracy reaches 80%or more in 150 seconds to enter the formal trials. Let participants complete formal trials under all experimental conditions described in the text manuscript, having them complete the input task in a random or a balanced order. Each pair, word, or sentence represents a trial, and different experimental designs produce different experimental conditions.After each condition, ask the participants to complete all the questionnaires at random to obtain subjective feedback. And allow them to rest for one minute. Express appreciation to participants with monetary or material rewards.This study was used to evaluate two keyboard layouts, namely the curved QWERTY and traditional QWERTY, with different sizes of buttons. The statistical analysis of the input performance, subjective feedback, and fitted ellipse of each button is shown here. The transition time between two keys with a small button size was significantly longer than that between keys with a large button size in the curved QWERTY.The word error rate of the traditional QWERTY was significantly lower than that of the curved QWERTY. The main effect of keyboard layout is significant in intent to use"and subjective workload, showing that participants perceive less subjective workload and are more likely to use the curved QWERTY when compared to the traditional QWERTY. The six dimensions of the subjective workload are shown here.In the area of the fitted ellipse, the interaction between keyboard layout and button size is significant, showing that for both small and large button size, the area of the traditional QWERTY is larger than that of the curved QWERTY. For both keyboard layouts, the area of the small button is smaller than that of the large button. In the offset of the fitted ellipse, the interaction between keyboard layout and button size is only significant in the offset in the Y direction.In the curved QWERTY, the offset in the Y direction of the small button is significantly shorter than that of the big button. Remember to keep the screen and participant's hand clean before experiment. Training tasks and balanced experimental conditions help to avoid the practice effect and other confounding factors.This protocol can be adopted in the evaluation of keyboard design in the touch screen of other smart devices, such as a wearable smart watches, tablet PC, and virtual reality devices.

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Research

JoVE Journal

Behavior

3.0K vistas.  Tsinghua University. This open source protocol and toolkit could inspire the novice to start their studies in keyboard designs, optimize the user experience, and improve the revenue of input method at the companies. This protocol provides a systematic method to evaluate the keyboard design more precisely on smartphones. Various highly accepted indicators, and the new special indicators are involved in this protocol.A novice researcher may be confused about choosing appropriate evaluating indicators, and ex...