This study assessed touchscreen interfaces for people with tetraplegia. It tested tapping interactions with targets of different sizes (7mm, 12mm, 17mm) in corner, edge, and vertical-center positions on the screen. 15 tetraplegic participants completed the tasks. The results showed target size significantly influenced error rates, with 12mm targets having the fewest errors. Target position (corner, edge, vertical) did not influence errors except that the largest targets (17mm) had fewer errors at the top and bottom of the screen compared to the center. Overall error rates remained high. The researchers suggest improving tapping techniques and conducting further studies comparing touchscreen interactions between able-bodied and tetraplegic users

1. Assessing Mobile
Touch Interfaces
for Tetraplegics
Tiago Guerreiro
Hugo Nicolau
Joaquim Jorge
Daniel Gonçalves

2. Mobile evolution …

3. Leading to …
Touch Interfaces

4. pleasant

5. Tactile feedback
loss of tactile
feedback

6. Loss of physical stability

7. hard to select targets

8. it occurs to everyone

9. … and motor
impaired

10. require less strength

11. Adapt to users’ needs

12. Provide the knowledge to
build better touch interfaces

13. We performed …

14. Tested several …
Interaction
Techniques

15. Screen areas …
… corners

16. Screen areas …
… edges

17. … and target sizes
7 mm 12 mm 17 mm

18. Tapping

19. Crossing

20. Exiting

21. Gesturing

22. 15 participants
28-64 years old
C4-C7 lesion level
6 left-handed
never used touchscreens

23. Focus on …
Tapping

24. Target Size
H0Target size has no influence
on task errors

25. Target Size

26. Target Size
H0Target size has no influence
on task errors
[F=25.110 p<.001]

27. Corner Targets
H0Task errors are not dependent
on the target’s position (corner
vs center)

28. Corner Targets
7mm 12mm 17mm
35% 35% 27% 27% 22% 22%
45% 24% 20%
35% 35% 27% 27% 22% 22%

29. Corner Targets
H0Task errors are not dependent
on the target’s position (corner
vs center)
[p>.05]

30. Edge Targets
H0Task errors are not
dependent on the target’s
position (edge vs center)

31. Edge Targets
7mm 12mm 17mm
45% 23% 22%
40% 26% 19%
45% 45% 23% 23% 22% 22%
45% 23% 22%

32. Edge Targets
H0Task errors are not
dependent on the target’s
position (edge vs center)
[p>.05]

33. Edge Targets
7mm 12mm 17mm
53% 27% 20%
Left 61% 33% 28% 11% 24% 22% 11% 11% 22%
37% 30% 13%
44% 33% 31%
Right 37% 44% 41% 41% 27% 7% 52% 23% 18%
53% 11% 7%

34. Vertical Areas
H0Task errors are not
dependent on the target’s
position (top vs bottom vs
center)

35. Vertical Areas
7mm 12mm 17mm
45% 28% 27%
39% 28% 24%
43% 19% 12%

36. Vertical Areas
H0Task errors are not
dependent on the target’s
position (top vs bottom vs
center)
Largest [p<.05]
Medium [p<.01]

37. Suggestions for...
Tapping

38. Regarding target size …
12 mm

39. However, error rates are still …
High

40. Regarding target position …
Support

41. Future Work
Remaining interaction techniques
Differences between able-bodied and tetraplegics

42. The End
Hugo Nicolau
hman@vimmi.inesc-id.pt