An Assessment Method and Toolkit to Evaluate Keyboard Design on Smartphones

Summary

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.

Abstract

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. It needs no additional or expensive equipment 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.

Introduction

Keyboard input is the mainstream method of the human-smartphone interaction^1,2, 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.

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Protocol

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.

Figure 1: General process of conducting a keyboard experiment and evaluating the keyboard design.

Results

The representative study is mainly following the mentioned protocol. The study adopts a 2 (Keyboard layout: Curved QWERTY vs. Traditional QWERTY) × 2 (Button size: large, 6.3 mm × 9 mm vs. small, 4.9 mm × 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 has not adopte.......

Discussion

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.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Changxiang 6S smartphone	Huawei		Smartphone used in the examplar study
Curved QWERTY keyboard software	Tsinghua University		Developed by authors
SPSS software	IBM		Data analysis software
G*Power software	Heinrich-Heine-Universität Düsseldorf		Sample size calculation
E4 portable wireless wristband	Empatica		Recording galvanic skin response and heart rate
Arqus	Qualysis		Motion capture camera platform
Passive marker	Qualysis		Appropriate sizes: 2.5 mm, 4 mm, and 6.5 mm
Trigno sEMG	Delsys		Recording electromyographic activity
Visual Studio Code	Microsoft		Python editor