## 1 Introduction  
### Motivation  
Nowadays, smartphones take a pivotal role in everyday life. With touchscreen input and various sensors, the smartphone enables humans to interact with computer systems in totally new ways. Many new interaction techniques surfaced with the smartphone, starting with simple gestures like swiping and ending with logging into a smartphone with face detection instead of typing a password. Despite all these exciting new interaction possibilities, text input, the most used interaction aspect with a smartphone, stayed mostly the same as with personal computers and notebooks. But why is it important to reevaluate that interaction and what are common problems with so-called soft keyboards?  
A big problem with soft keyboards, also called virtual keyboards, is the lower text entry speed, measured in words per minute (WPM), in comparison with an actual physical keyboard. The average user of a soft keyboard inputs text at about 36 words per minute. This is about 15 words per minute less than users using an actual physical keyboard [1]. This means that tasks carried out with a smartphone can take up to 30% longer compared with tasks carried out on a personal computer or notebook. A soft keyboard has several additional challenges, for example the smaller size, lack of haptic feedback, and occlusion.  
Nonetheless, users execute more and more tasks on their mobile devices and therefore it is definitely important to increase the usability and speed of textual input with a smartphone [2]. Despite all the mentioned disadvantages, smartphones will be used due to their unprecedented accessibility and handiness for quick tasks and increasingly for longer tasks. This handiness and portability should not decrease the efficiency of the user. There should not be a trade-off between efficiency and portability.  
The soft keyboard is the main bottleneck of text input. While companies like Google try to improve the usability of soft keyboards with touch prediction and language models for auto-correction and auto-completion [3], the standard layout remains the Qwerty layout. Generally, most mobile phones have a default Qwerty keyboard layout, which is never changed by the user. According to [PERSON] et al. [1] 87% of all smartphone users type with a Qwerty keyboard layout. The Qwerty layout is not even optimal for use with physical keyboards. It is not optimized in the domain of letter frequency and words in a corpus unlike for example the Dvorak layout [4]. The Qwerty layout is even less optimal for use with soft keyboards on mobile phones [4; 5]. There are several optimized keyboard layouts like Opti or Metropolis, which all increase typing speed by decreasing the traveled distance between keys according to Fitts' Law [6]. Nonetheless, as already mentioned, most users type their text with the preconfigured Qwerty layout. This is similar to the non-adoption of high-performance layouts for physical keyboards. The reason for this non-adoption in both cases might be the decreased typing performance coming from the unfamiliarity of the layout, which increases the visual search times and therefore decreases the typing speed [6; 7]. This so-called novice experience is the entry barrier for users to adapt to high-performance layouts. This means that, despite the gain after learning the new keyboard, the user is not willing to experience a temporary decreased typing performance and increased effort. This paper tries to diminish this barrier by helping the user with the visual search of the next key with a new keyboard layout and therefore increasing the typing speed until the user is familiar with the new keyboard layout. This should be achieved by comparing different visual clues to improve the visual search by highlighting the next most probable characters on a keyboard.