Thumbs up for faster texting
Researchers at the University of St Andrews, the Max Planck Institute for Informatics and Montana Tech have created a new keyboard that enables faster thumb-typing on touchscreen devices.
The new system, dubbed KALQ, after the order the keys appear in the keyboard (in the tradition of QWERTY), allows people to thumb-type 34 per cent faster on tablets.
To create KALQ, the team used computational optimisation techniques, in conjunction with a model of thumb movement, to search among millions of potential layouts before identifying one that yields superior performance.
Dr Per Ola Kristensson, Lecturer in Human Computer Interaction in the School of Computer Science at the University of St Andrews, said: “The legacy of QWERTY has trapped users with suboptimal text entry interfaces on mobile devices.
“However, before abandoning QWERTY, users rightfully demand a compelling alternative. We believe KALQ provides a large enough performance improvement to incentivise users to switch and benefit from faster and more comfortable typing.”
Two-thumb typing is ergonomically very different from typing on a physical keyboard. The QWERTY layout is ill-suited for tablets and other touchscreen devices when typing with both thumbs.
It is established that normal users using a QWERTY on a touchscreen device are limited to typing at a rate around 20 words per minute, which is slow compared to the entry rates users can typically achieve on physical keyboards.
By rearranging the keys on the keyboard layout it is possible enable faster thumb typing. However, the researchers quickly realised that slight changes of the layout, like exchanging a few keys, would not be sufficient for a significant improvement.
Words like “on, see, you, read, dear, based”, frequently used in texts, have to be typed on a split-QWERTY layout with a single thumb only. This makes the typing process cumbersome and slow. This insight initiated the process to develop a layout for two-thumb text entry that could speed up typing and minimise strain for the thumbs.
Dr Antti Oulasvirta, Senior Researcher at the Max Planck Institute for Informatics in Germany, said: “The key to optimising a keyboard for two thumbs is to minimise long typing sequences that only involve a single thumb. It is also important to place frequently used letter keys centrally close to each other.
“Experienced typists move their thumbs simultaneously: while one thumb is selecting a particular key, the other thumb is approaching its next target. From these insights we derived a predictive behavioural model we could use to optimise the keyboard.”
The computational optimisation process had two goals: to minimise the moving time of the thumbs and to enable typing on alternating sides of the tablet as well as possible.
The results achieved by the computational optimisation procedure was surprising: in the new keyboard KALQ, all vowels, with the exception of the letter “y” (which can be regarded as both a vowel and a consonant), are placed in the area assigned to the right thumb, whereas the left thumb is assigned more keys.
To fully benefit from this layout, participants in the user study were trained to move their thumbs simultaneously. While one thumb is approaching an intended letter key, the other thumb moves to its next target.
Finally, the authors developed probabilistic error correction methods that took into account the nature of thumb movements and statistical knowledge about the text users are typing. The error correction algorithm enabled trained users to speed up while retaining an acceptable error level.
With these improvements, users were able to reach 37 words per minute, which is the highest ever reported entry rate for two-thumb typing on touchscreen devices, significantly higher than the approximately 20 words per minute entry rate users can normally reach on a regular split QWERTY layout.
The researchers will present their work at the CHI 2013 conference (the ACM Conference on Human Factors in Computing Systems) in Paris on May 1st. CHI serves as the principal international forum for outstanding research and development in human-computer interaction.
KALQ will be available as a free app for Android-based smartphones.
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Issued by the Press Office, University of St Andrews
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Ref: (KALQ 24/04/13)
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