# A Study of Model Iterations of Fitts' Law and Its Application to Human-Computer Interactions
## 4 Some Studies of Fitts' Law in HCI Scenes
### Touchscreen Scenes
#### 4.1.1 Small Touchscreen  
Our contact with restricted display areas has expanded substantially with the advent of small-screen devices, including smartphones [46]. User interface buttons are frequently resized to accommodate smaller screens, which presents design issues and calls for optimization for efficient finger interactions. [PERSON] et al. improved [PERSON]'s initial modelby extending Fitts' law to small-size targets [2; 47]. Additionally, by utilizing probabilistic insights, researchers such as [PERSON] et al. have dug deeper into assessments of finger-touch input. [PERSON] et al. introduced the Fitts law, a revision of Fitts' law that analyzes the movement endpoint distribution as a mix of speed-accuracy control and the finger touch distribution. This sophisticated model delivers greater accuracy in simulating finger-touch inputs compared to the classic Fitts' law approach [48].  
On small-screen devices, the majority of users prefer one-handed touch interactions. Fitts' law was utilized by [PERSON] et al. to evaluate thumb motor performance during one-handed touch interactions. They observed that thumb performance can be improved by smaller phone sizes [49]. The natural thumb position was defined by [PERSON] et al., who also showed that one-handed movement within 45 mm of this location preserves optimal task performance [50]. Smaller buttons cause users to make more mistakes and take longer to move (MT), while larger buttons result in lower error rates and less finger strength being used [51; 52]. [PERSON] et al. offered particular quantitative insights, demonstrating a considerable increase in movement time when the icon size was less than 110 response pixels. Additionally, participants stated that when the icon's size increased to 140 response pixels, clicking became easier [53]. Multi-touch actions including pinching, turning, and dragging are frequently used when using smartphones. Based on Fitts' law, [PERSON] et al. created a model that provides useful guidance for designing products with multi-touch interfaces [54].  
Variations in handheld posture, hand tremors, and surrounding noise can all have a big impact on how well cell phones function when used in motion [55]. A study by [PERSON] et al. showed that using a button size of 14 \(\times\) 14 mm reduced error rates when standing and walking, emphasizing the importance of this size for cell phone screen design [56]. [PERSON] et al. reported a drop in click accuracy when users engaged in walking, with distinct gait phases impacting operation precision. It is interesting to see that utilizing the index finger instead of the thumb produced better results when using the phone. According to the study, walking at a pace equivalent to 75% of one's normal pace while using a phone can also improve the accuracy of the offset model [57].  
A few things that affect interactive performance on small-screen interfaces are button size, device size, walking distractions, and operating mode selection. When creating interfaces for small-screen devices, designers must take all of these factors into account to maximize user experiences.