Assessing  Mobile  Touch Interfaces  for Tetraplegics Tiago Guerreiro Hugo Nicolau Joaquim Jorge Daniel Gonçalves
Mobile  evolution  …
Touch Interfaces Leading to …
pleasant
Tactile feedback loss of tactile feedback
Loss of physical stability
hard to select targets
it occurs to everyone
…  and motor impaired
require less strength
Adapt to users’ needs
Wobbrock,  EdgeWrite , 2003  Froehlich,  Barrier Pointing , 2007
Provide the knowledge to build better touch interfaces
We performed …
Tested several … Interaction Techniques
Screen areas … …  corners
Screen areas … …  edges
Screen areas … …  middle areas
7 mm …  and target sizes 12 mm 17 mm
Tapping
Crossing
Exiting
Gesturing
15 participants 28-64 years old C4-C7 lesion level 6 left-handed never used touchscreens
Focus on … Tapping
Target Size H0 Target size has no influence on task errors
Target Size
Target Size H0 Target size has no influence on task errors [F=25.110  p<.001]
Corner Targets H0 Task errors are not dependent on the target’s position (corner vs center)
7mm 12mm 17mm Corner Targets 35% 35% 27% 27% 22% 22% 45% 24% 20% 35% 35% 27% 27% 22% 22%
Corner Targets H0 Task errors are not dependent on the target’s position (corner vs center) [p>.05]
Edge Targets H0 Task errors are not dependent on the target’s position (edge vs center)
7mm 12mm 17mm Edge Targets 45% 23% 22% 45% 40% 45% 23% 26% 23% 22% 19% 22% 45% 23% 22%
Edge Targets H0 Task errors are not dependent on the target’s position (edge vs center) [p>.05]
7mm 12mm 17mm Edge Targets Left Right 53% 27% 20% 61% 33% 28% 11% 24% 22% 11% 11% 22% 37% 30% 13% 44% 33% 31% 37% 44% 41% ...
Vertical Areas H0 Task errors are not dependent on the target’s position (top vs bottom vs center)
7mm 12mm 17mm Vertical Areas 45% 28% 27% 39% 28% 24% 43% 19% 12%
Vertical Areas H0 Task errors are not dependent on the target’s position (top vs bottom vs center) Largest [p<.05] Medium ...
Suggestions for... Tapping
Regarding target size … 12 mm
However, error rates are still … High
Regarding target position … Support
Remaining interaction techniques Differences between able-bodied and tetraplegics Future Work
The End Hugo Nicolau [email_address]
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Assessing mobile touch interfaces for tetraplegics

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  • Mobile Evolution As you know, in the past two decades we have witness an evolution in mobile devices
  • That is leading us to touch interfaces. These stylish devices are replacing traditional keypads in mobile phones and provide a more
  • a more engaging and pleasantness user experience and promise to be more effective and efficient than their predecessors
  • However, these devices lost an important feature, their tactile feedback, thus
  • one may argue that touch interfaces lost the physical stability provided by their button-based counterparts. Indeed, these devices are highly physical demanding
  • Due to the absence of tactile affordances, touch screens make it harder for people to accurately select targets
  • This problem occurs to everyone, particularly when situational impaired due to tremor. For instance, when you are walking ou in a bus
  • But also with motor disabled users who suffer from lack of precision when moving their upper limbs.
  • On the other hand, touch screens also presents as a good opportunity for motor disabled people, since they are less demanding than keypads, regarding the strengh required to select a target.
  • Also these interfaces can adapt themselves to their users, making it possible to design interfaces that fit the users’ capabilities
  • In fact, there have been successful efforts to improve access to mobile touch screens. Examples include EdgeWrite or Barrier Pointing. Both techniques take advantage of the remaining physical properties of these devices, the edges.
  • The challenge is to understand how tetraplegic people use touch screens and to find a way to build better touch interfaces. Our goal with this work is to provide this knowlage … However, there is no compreensible knowledge how to build better touch interfaces. Therefore, we believe that a step back is required in order to fill this gap
  • To overcome this we have performed extensive user evaluations with 15 tetraplegic people
  • And explored several screen areas such as corners
  • and edges, because these two areas are usually used to provide additional physical support to the users. Examples of previous works include edgewrite or barrier ponting
  • And explored several screen areas such as corners, and edges
  • and also exploring target characteristics, as their size
  • The first interaction technique was tapping. T his is the most used technique in current touch screen devices. We just need to touch in order to select a target. This could be done in the middle areas, corners or edges.
  • In the second technique users had to cross the target in order to select it. This was performed in the middle areas
  • Exiting was similar to Crossing, but a selection was acknowledged by performing a gesture towards the screen edge or corner and crossing the intended target
  • Gesturing was the only technique that did not require a target selection. Users could perform directional gestures anywhere on the device’s surface
  • We recruited 15 tetraplegic participants (two females, thirteen males) averaging 42 years old, from a physical rehabilitation center. All participants had some residual arm movement. All user possessed a mobile phone, but most never experienced with a touch screen before
  • I have described to you all experience, However, in this paper we have only looked at a particular method and thus, on a subset of the described experience, which is tapping. Also we were particularly interested in accuracy rates.
  • First of all, we want to see if target size had influence on task errors. This was our hypothesis
  • As we can see here accuracy increases with target size reaching a 20% error rate. There was a significant effect on Task Errors between the small and both medium and larger sizes. These results indicate 12 mm as an approximate suitable value, since there was no significant differences between the two largest sizes. Therefore, for UI designers this may be a good commitment between error rate and required space. However, participants still had a 20% error rate which is significantly high.
  • We can reject our hypothesis and conclude that target size has influence on task errors
  • Regarding corners, the lack of control in users’ movements suggests that additional support may improve their performance. We tested whether taping a target in the corner of the screen is indeed easir than tapping a target in any other position.
  • These are the results for all sizes, and we found no significant effect of target position on task errors. Only a minor effect was found on the smallest size, with less errors in the corners.
  • Therefore corner targets do not influence error rates
  • Regarding edge targets we did a similar analysis
  • And, again, we could not find any significant difference on task errors between tapping on the edge or not.
  • So, we have this .. However,
  • we did found an interesting interaction between the preferred arm and the error rate on a specific edge for medium and largest size. Results indicate that targets near the users support, or preferred hand are easier to tap.
  • For vertical areas we divided the screen vertically in 3 areas, top, center and bottom and tested our hypothesis
  • and we found a significant difference in both medium and largest sizes, with the bottom areas being easier to select.
  • Thus, vertical areas influence task errors
  • The most relevant implication suggested by these evaluations is that motor disabled users can operate devices with different success rates depending on screen position. While able bodied people can easily adjust the device to their convenience, tetraplegic users have less freedom to interact with the device
  • As for size, results showed that error rates start to level off above 12 mm, which indicates that a good target size would be around this value.
  • Error rates are still high when compared to previous reports of able bodied users performance even when situationally impaired being around 10%
  • Concerning target positioning, it is easier to select targets near users’ support or preferred hand. One limitation of this evaluation was the small number of left-handed users, which limits our conclusions on target locations on the screen, a particular good corner or good edge for each hand
  • In the future, we will analyze more interaction techniques and the relationships between them. We will also analyze the differences between tetraplegics and able-bodied people in greater depth, in order to understand where they diverge and identify where extra attention is required when designing touch interfaces.
  • Assessing mobile touch interfaces for tetraplegics

    1. 1. Assessing Mobile Touch Interfaces for Tetraplegics Tiago Guerreiro Hugo Nicolau Joaquim Jorge Daniel Gonçalves
    2. 2. Mobile evolution …
    3. 3. Touch Interfaces Leading to …
    4. 4. pleasant
    5. 5. Tactile feedback loss of tactile feedback
    6. 6. Loss of physical stability
    7. 7. hard to select targets
    8. 8. it occurs to everyone
    9. 9. … and motor impaired
    10. 10. require less strength
    11. 11. Adapt to users’ needs
    12. 12. Wobbrock, EdgeWrite , 2003 Froehlich, Barrier Pointing , 2007
    13. 13. Provide the knowledge to build better touch interfaces
    14. 14. We performed …
    15. 15. Tested several … Interaction Techniques
    16. 16. Screen areas … … corners
    17. 17. Screen areas … … edges
    18. 18. Screen areas … … middle areas
    19. 19. 7 mm … and target sizes 12 mm 17 mm
    20. 20. Tapping
    21. 21. Crossing
    22. 22. Exiting
    23. 23. Gesturing
    24. 24. 15 participants 28-64 years old C4-C7 lesion level 6 left-handed never used touchscreens
    25. 25. Focus on … Tapping
    26. 26. Target Size H0 Target size has no influence on task errors
    27. 27. Target Size
    28. 28. Target Size H0 Target size has no influence on task errors [F=25.110 p<.001]
    29. 29. Corner Targets H0 Task errors are not dependent on the target’s position (corner vs center)
    30. 30. 7mm 12mm 17mm Corner Targets 35% 35% 27% 27% 22% 22% 45% 24% 20% 35% 35% 27% 27% 22% 22%
    31. 31. Corner Targets H0 Task errors are not dependent on the target’s position (corner vs center) [p>.05]
    32. 32. Edge Targets H0 Task errors are not dependent on the target’s position (edge vs center)
    33. 33. 7mm 12mm 17mm Edge Targets 45% 23% 22% 45% 40% 45% 23% 26% 23% 22% 19% 22% 45% 23% 22%
    34. 34. Edge Targets H0 Task errors are not dependent on the target’s position (edge vs center) [p>.05]
    35. 35. 7mm 12mm 17mm Edge Targets Left Right 53% 27% 20% 61% 33% 28% 11% 24% 22% 11% 11% 22% 37% 30% 13% 44% 33% 31% 37% 44% 41% 41% 27% 7% 52% 23% 18% 53% 11% 7%
    36. 36. Vertical Areas H0 Task errors are not dependent on the target’s position (top vs bottom vs center)
    37. 37. 7mm 12mm 17mm Vertical Areas 45% 28% 27% 39% 28% 24% 43% 19% 12%
    38. 38. Vertical Areas H0 Task errors are not dependent on the target’s position (top vs bottom vs center) Largest [p<.05] Medium [p<.01]
    39. 39. Suggestions for... Tapping
    40. 40. Regarding target size … 12 mm
    41. 41. However, error rates are still … High
    42. 42. Regarding target position … Support
    43. 43. Remaining interaction techniques Differences between able-bodied and tetraplegics Future Work
    44. 44. The End Hugo Nicolau [email_address]

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