Evaluating Touch Gesture Usability

Evaluating Touch Gesture Usability Kevin Arthur Synaptics UPA 2010 1

Multi-Finger TouchPad Gestures Two-Finger Two-Finger Three-Finger Pinch Zoom Rotate Flick Two-Finger Two-Finger Three-Finger Scroll Pivot Rotate Press 3

Motivation for Testing Gestures • Formative usability tests for feedback to developers Audience • Summative and competitive usability tests for sales, OEM partners • Need for repeatable procedures • Do users understand the gestures? Questions • Can users successfully perform the gestures? • Are gestures satisfying to use? • Holistic evaluation; test with users in a realistic scenario on a working system Context • Different from pure data collection for testing gesture recognizer offline 4

Important Properties of Gestures • Gestures must be taught; testing the Lack of Affordances documentation is important • Performance is not always predictable Nondeterministic • Recognition trade-offs exist between and Interdependent gestures in same parameter space • Gestures should be evaluated as a set Interface • TouchPad’s primary use is still for pointing and scrolling; gestures Overloading shouldn’t interfere User Variation • Hand size, long fingernails 5

Phases in Performing a Gesture • Introduction through Exposure documentation or prior use • Initial touch contact and motion Registration for gesture recognition • Gesture is registered and “locked in” – mode switch Continuation • Dynamic phase with relaxed motion requirements Termination • End position, fingers lifting 6

Test Framework Step Objective Assess understanding, help 1 Gesture Introduction materials [Exposure phase] Familiarization and 2 Train to basic performance Practice Task [All phases] Obtain rates of correct and incorrect gesture recognition 3 Accuracy Task [Registration phase] Assess satisfaction, ease of use Satisfaction Questionnaire 4 and Debrief [All phases] 7

Gesture Introduction Simulate new user experience • “Out of box experience” material • Help videos • Try the gesture until success • If no success, moderator assists 8

Familiarization and Practice Tasks: Pinch Zoom Zoom in on the South Residences, near the top of the map, and find the building called The Knoll. Zoom all the way in on The Knoll and then zoom all the way back out. 2000 × 2000 pixels or higher. Approximately five pinch-zooms required. 9

Flick and Rotate 1. Use the rotate gesture to make the image upright. 2. Type the image’s title into the caption field and press Enter. 3. Use the flick gesture to go to the next image. 11

Flick and Rotate 12

Accuracy Task User performs a set number of gesture attempts Moderator records table of system responses. Example: No Misrecognized Other/ Gesture Correct Response As Pinch As Rotate Notes Pinch Zoom 7 2 - 1 In Pinch Zoom 8 2 - 0 Out “requires Rotate 6 3 1 - too large a Clockwise motion” Rotate Counter- 7 1 2 - clockwise 13

Accuracy Results Unified Measure 100% 90% 80% 70% 60% 50% Misrecognized 40% No Response 30% Correct 20% 10% 0% Pinch Pinch Rotate CW Rotate Average Zoom In Zoom Out CCW 14

Accuracy Results, Competitive Study System A System B Average Correct 82% Average Correct 89% 100% 100% 90% 96 90% 94 96 94 90 88 80% 80% 85 82 83 70% 70% 73 60% 60% 61 50% 50% 40% 40% 30% 30% 20% 20% 10% 10% 0% 0% 2F Pinch 2F Rotate 3F Flick 3F Flick 2F Scroll 2F Pinch 2F Rotate 3F Flick 3F Flick 3F Press 2F Scroll Zoom LR UD Zoom LR UD Correct No response Incorrect Correct No response Incorrect 15

Accuracy Results, Competitive Study Correct Gesture Recognition Rates 120 100 80 Correct (%) System A 60 System B System C 40 20 98 100 97 62 77 68 92 86 93 97 97 100 0 Pinch Rotate Flick Three-Finger Press 16

Satisfaction Questionnaire 17

Satisfaction Questionnaire 18

Questionnaire Result I would use this gesture if it were available (strongly disagree = 1, strongly agree = 9) Pinch 7.38 Rotate 4.38 3F 7.88 Flick 3F 8.75 Press 2F 8.25 Scroll 1 2 3 4 5 6 7 8 9 Strongly Strongly Disagree Agree 19

Questionnaire, Competitive Rating Format How well do the gestures work on each system? Please rate from 1 (Poor) to 5 (Excellent) Gesture System A System B System C Pinch Zoom Rotate N/A Flick Left-Right Flick Up-Down N/A Three-Finger Press N/A N/A Two-Finger Scrolling 20

Ratings Results User Ratings With 95% Confidence Intervals Excellent 5 4 3 2 Poor 1 Pinch Zoom 2F Rotate 1F Rotate Flick LR Flick UD 1F Scroll 1F Scroll 2F Scrolling (Chiral) (Linear) (Circular) System A System B System C 21

Related Tests & Gesture Side-Effects Other usability tests for notebook input devices • Pointing (target acquisition) • Drag and drop • Scrolling • Typing and accidental TouchPad input Assess gesture side-effects • Unintended gestures • Other issues 22

Conclusions Properties of gestures call for careful testing • Gesture introduction and documentation is key • Gestures are nondeterministic – less predictable • Gestures are interdependent; test as a set Framework of gesture tests 1. Gesture Introduction 2. Familiarity and Practice Tasks 3. Accuracy Tasks 4. Satisfaction Questionnaire and Debrief 5. Related Tests & Gesture Side-Effects 23

Resources References • Sylvia Le Hong and Dan Mauney, “Cultural Differences and Similarities in the Use of Gestures on Touchscreen User Interfaces,” UPA 2010. blog.humancentric.com/gesture-research/ • Mark Billinghurst and Bill Buxton, “Gesture Based Interaction” in Human Input to Computer Systems (draft), www.billbuxton.com/inputManuscript.html • Dan Saffer, Designing Gestural Interfaces, O’Reilly 2008. • Craig Villamor, Dan Willis, Luke Wroblewski, Touch Gesture Reference Guide, www.lukew.com/touch/ • Jacob Wobbrock , Meredith Ringel Morris, Andrew Wilson, “User- Defined Gestures for Surface Computing,” CHI 2009. • Mike Wu, Chia Shen, Kathy Ryall, Clifton Forlines, Ravin Balakrishnan, “Gesture Registration, Relaxation, and Reuse for Multi-Point Direct- Touch Surfaces,” IEEE Tabletop 2006. Contact • karthur@synaptics.com, touchusability.com Acknowledgments • Usability colleagues at Dell, HP, Lenovo, Synaptics 24

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Evaluating Touch Gesture Usability

by Kevin Arthur on May 30, 2010

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