Breaking Fitts's Law

Transcript

1. Breaking Fitts’s Law
   

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2. Is it faster to click on
   targets at the edge of
   the screen?
   

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3. 1680 x 1080
   

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6. Bounding line simulates edge of screen
   

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7. Bounding line simulates edge of screen
   

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12. Theoretical Underpinnings:
    Targets at the edge of the screen
    effectively have infinite width
    

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13. W = ∞
    

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14. W
    

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15. Are movement times lower while
    selecting targets at the edge of the screen
    than predicted by Fitts’ law?
    Objectified Question
    

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16. Does the magnitude of effect vary based
    on target size?
    Additional Questions
    

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17. Bounded mouse movements will be
    faster than Fitts’ Law would predict.
    Hypothesis 1
    

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18. Bounded mouse movements will be
    faster than identical unbounded
    movements.
    Hypothesis 2
    

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19. Simulate the edge of the screen with a
    ‘bounding box.’
    Participants perform an identical set of
    pointing tasks with a bounding box and
    without one.
    Design
    

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20. Addressing Potential Confounds
    Screen Resolution Consistent at 1680x1080
    Subject Distance from Screen Same chair height and distance from monitor
    Type of Mouse Use of identical Dell optical mouse
    Use of Trackpad Mandated use of Trackpad
    Order of Trials Randomized trials to eliminate order effects
    Device LCD with identical calibration and constrast
    Starting Position Always in the center of the screen
    

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21. Methodology
    1680x1080 Resolution
    22” Display
    2 Foot distance from Display
    Targets are 1º and 1.2º of Visual Angle
    Dell optical mouse
    Randomized order of trials
    10 second break after 25 trials to reduce fatigue
    Bright green targets on black background
    Pink bounding border
    Trial time = Time from start until successful click
    0.5s fixation time as cursor is auto-centered.
    Cursor always starts at center of screen
    8 varying target distances
    Two distinct target sizes
    Same set of targets
    4 participants
    

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22. We used the Least-of method of determining target with
    in two-dimensions, which MacKenzie and Buxton (1992)
    found to be comparable to the W’ Model (actual target
    depth along the approach vector).
    

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23. t=-5.7272
    p<0.05
    t=0.1196
    p=0.9
    t=-7.8984
    p<0.05
    Condition
    Average (Observed MT)
    Average Observed MT vs. Condition
    

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24. Correlation
    No Bounding Box Bounding Box
    0.9
    0.7
    0.5
    0.3
    0.1
    

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25. Differences of Observed Time and Predicted Time
    

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26. Data
    Observed MT vs. Predicted MT (Large targets with Bounding Box)
    

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27. Data
    Observed MT vs. Predicted MT (Large Targets with No Bounding Box)
    

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28. Data
    Observed MT vs. Predicted MT (Small targets with Bounding Box)
    

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29. Data
    Observed MT vs. Predicted MT (Small Targets with No Bounding Box)
    

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30. Independent Variables:
    Presence of Bounding Line
    Size of Target
    Dependent Variable:
    Observed Movement Time
    

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31. ★ Perform test on tablet with physical bounding
    boxes
    ★ Test sizes between 20px and 100px to find out
    when size becomes insignificant.
    ★ Test for External Validity
    ★ Compare differences in accessibility of tabs
    between browsers:
    ★ Chrome on Windows and Mac OS X
    ★ Chrome and Firefox
    Next Steps
    

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