Presentation @ CHI'12

1. Touch Typing using Thumbs:
Understanding the Effect of
Mobility and Hand Posture
Hugo Nicolau
hman@vimmi.inesc-id.pt
Joaquim Jorge

3. SIID
Situationally-Induced Impairments and Disabilities

4. Hand oscillation hinder performance
[Bergstrom-Lehtovirta et al., 2011]

5. Especially with small virtual targets
[Mizobuchi et al., 2005; Lin et al., 2007]

6. Thumb interaction

7. Text-entry whilst walking

8. Effects of walking and hand posture
on touch typing

9. 22 participants
19 males, 3 females
23 to 40 years old
Right-handed

10. Only 15
used mobile
touchscreens
regularly

11. 3 mobility conditions
Seated Walking Walking
65% of human pace Average human pace
[Barnard et al., 2005] 2 steps / second

12. Indoor test track and Pacesetter
Fixed pace [Kane et al., 2008]
Comparable level of walking demand
Vibrotactile feedback to pacesetter

13. Hand Postures
Two-hand Two-hand One-hand
portrait landscape portrait

14. Copy task
2 practice sentences / condition
5 test sentences / condition
Portuguese language
representative corpus
Error correction was not
available

15. Apparatus
HTC Desire
7x10 mm – portrait mode
10x10 mm – landscape mode
Neither word prediction nor
correction was used

16. Experiment Design
22 participants x 3 mobility settings x 3 hand postures
990 sentences overall
Two-way repeated measures
analysis

17. Results

18. Two-hand input is faster
Words per Minute
35
28.1 29.1 28.9
30 23.9 25.0 24.4
25
19.9 20.5 20.0
20
15
10
5
0
One-hand portrait Two-hand portrait Two-hand landscape
Seated Walking (65%) Walking (100%)

19. Two-hand posture does not provide
additional stability
MSD Error Rate by Hand Oscillation
16%
seated walking (65%) walking (100%)
14%
12%
10%
8%
6%
4%
2%
0%
0.0 g 0.5 g 1.0 g 1.5 g 2.0 g
One-Hand Portrait Two-Hand Portrait Two-Hand Landscape

20. Substitutions are the most common
type of error
8% 0.6% 1.8%
1.0%
0.9%
6% 0.6% 0.8%
1.1% 1.2% 1.4%
1.1% 0.9%
1.1% 1.2%
4% 7.0% 1.0%
5.2% 5.5% 1.0% 0.8%
2% 4.3% 4.8% 0.8%
3.8% 0.7%
3.0%
0%
1.7% 1.8%
Del Ins Subs

21. Hand oscillation causes poor aiming
nor finger slips
Substitutions: incorrect land-on
120%
87% 93% 96%
100% 88% 92% 93% 84% 87% 81%
80%
60%
40%
20%
0%
One-hand portrait Two-hand portrait Two-hand landscape
Seated Walking (65%) Walking (100%)

22. Substitution pattern
Same-row errors
Distance of one key
Typically at the right
Pattern was consistent across mobility demands

23. Most users prefer larger keys
Participants Preference
18
16
14
12
10
8
6
4
2
0
One-hand portrait Two-hand portrait Two-hand landscape
Preferred hand posture Less preferred hand posture

24. Design Implications
(For all those sleeping/bored … WAKE UP!)

25. !Do not over rely on two-hand
interaction for physical stability
~

26. !Take advantage of typing
behaviors
T Y
transcribed > payyern
intended > pattern

27. !Design for poor aiming, especially
whilst mobile
Touch
+ Intended key
Accelerometer data

28. Conclusion
Negative effect of walking on touch
typing using thumbs
Consistent substitution pattern
Two-hand interaction does not improve text-entry
accuracy; Increasing target size is an effective
solution
Design implications

29. The End.
Hugo Nicolau
hman@vimmi.inesc-id.pt
http://web.ist.utl.pt/hugo.nicolau/