Breaking Fitts's Law

Transcript

1. Breaking Fitts’s Law
2. Is it faster to click on targets at the edge of the screen?
3. 1680 x 1080
6. Bounding line simulates edge of screen
7. Bounding line simulates edge of screen
12. Theoretical Underpinnings: Targets at the edge of the screen effectively have infinite width
13. W = ∞
14. W
15. Are movement times lower while selecting targets at the edge of the screen than predicted by Fitts’ law? Objectified Question
16. Does the magnitude of effect vary based on target size? Additional Questions
17. Bounded mouse movements will be faster than Fitts’ Law would predict. Hypothesis 1
18. Bounded mouse movements will be faster than identical unbounded movements. Hypothesis 2
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
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
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
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).
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
24. Correlation No Bounding Box Bounding Box 0.9 0.7 0.5 0.3 0.1
25. Differences of Observed Time and Predicted Time
26. Data Observed MT vs. Predicted MT (Large targets with Bounding Box)
27. Data Observed MT vs. Predicted MT (Large Targets with No Bounding Box)
28. Data Observed MT vs. Predicted MT (Small targets with Bounding Box)
29. Data Observed MT vs. Predicted MT (Small Targets with No Bounding Box)
30. Independent Variables: Presence of Bounding Line Size of Target Dependent Variable: Observed Movement Time
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