RMH: Fitts’ Law
RMH: Fitts’ Law. Paul Cairns paul.cairns@york.ac.uk. A law?!?!. One of the few in HCI Predictive Reliable Valuable research tool!. Today’s objectives. Fitts’ Law Theoretical basis Adaptations for HCI Implications for design Thoughts on modelling. Overview. Model for prediction
RMH: Fitts’ Law
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Presentation Transcript
RMH: Fitts’ Law Paul Cairns paul.cairns@york.ac.uk
A law?!?! • One of the few in HCI • Predictive • Reliable • Valuable research tool! ARMH: Fitts' Law
Today’s objectives • Fitts’ Law • Theoretical basis • Adaptations for HCI • Implications for design • Thoughts on modelling ARMH: Fitts' Law
Overview • Model for prediction • Time to point • Difficulty of target ARMH: Fitts' Law
A demo Interactive Fitts' Law talk • Not quite accurate! ARMH: Fitts' Law
Fitts’ Proposed Law • D • 1/W • a, b • Log? ARMH: Fitts' Law
Theory (or Analogy?) • Analogy with Shannon information • Meyer’s derivation • MacKenzie’s improvement ARMH: Fitts' Law
Terms • Index of difficulty • bits • Index of Performance, 1/b • bits per second ARMH: Fitts' Law
Impact in HCI • Reduce ID • Bigger icons, more space • Compare IP • “Capacity” of input devices • Put things in edges and corners ARMH: Fitts' Law
Deconstructing Fitts • Ecological validity • Construct validity ARMH: Fitts' Law
What Fitts did: W D ARMH: Fitts' Law
Let’s have a go! ARMH: Fitts' Law
What we apply it to: ARMH: Fitts' Law
Correcting for W • W’ – actual cross-section • Smaller of W and H • Area, W x H • Sum, W + H • Stick with W • Which is best? ARMH: Fitts' Law
Implications debunked • Edges are better • Corners are best • What about closeness of targets? • Mice are non-linear anyway! ARMH: Fitts' Law
What remains? • D/“W” is key • Target size (angle) • Stopping range (proportion) • Non-linear (concave), monotonic • Quite possibly log function • IP is meaningful • a is important ARMH: Fitts' Law
Toolbars • This is annoying not useful • Edges and corners? ARMH: Fitts' Law
Novel interactions • Artificially increasing W • “Sticky” buttons • Bubbles • Changing select • Goal-crossing ARMH: Fitts' Law
Novel devices • Comparing IP • iPhone • Wii • Kinect • Eye Gaze ARMH: Fitts' Law
Thoughts on Modelling • Is it a good model? • Yes, it fits the data • No, we don’t know why! • Could we produce a better one? • How? ARMH: Fitts' Law
Advanced Fitts’ Law • Fitts’ law as a model • Steering law • Games • Menu navigation • VE/VR? ARMH: Fitts' Law
Reading for today • MacKenzie (1992) Fitts’ Law as a Research and Design Tool…, HCI (7), 91-139 • MacKenzie & Buxton (1992) Extending Fitts’ Law to 2d tasks, CHI 1992, 219-226 • Interaction Design, 2nd edn • Cockburn & Firth (2003) Improving the acquisition of small targets. BCS HCI 03, 181-196 • Accot & Zhai (1997) Beyond Fitts’ Law… ACM CHI 97, 295-302 ARMH: Fitts' Law
