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A Comparison of Consecutive and Concurrent Input Text entry Techniques for Mobile Phones

A Comparison of Consecutive and Concurrent Input Text entry Techniques for Mobile Phones. Daniel Wigdor & Ravin Balakrishnan. Text Messaging. Estimated 500,000,000,000 text messages in 2003 worldwide More popular outside North America. Ambiguity. Pressing “2” : {2,a,b,c,A,B,C}. Problem.

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A Comparison of Consecutive and Concurrent Input Text entry Techniques for Mobile Phones

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  1. A Comparison of Consecutive and Concurrent Input Text entry Techniques for Mobile Phones Daniel Wigdor & Ravin Balakrishnan

  2. Text Messaging • Estimated 500,000,000,000 text messages in 2003 worldwide • More popular outside North America

  3. Ambiguity • Pressing “2” : {2,a,b,c,A,B,C}

  4. Problem • Multiple selection actions required • MacKenzie & Soukoreff: • Between group selection: {2,a,b,c,A,B,C} • Within group selection: {a}

  5. Consecutive Selection • Most prior techniques consecutive: • First make between group selection • Then make within group selection, or disambiguation of automatic selection • MultiTap, T9, 2-Key, LetterWise, WordWise… • What about selecting concurrently?

  6. Concurrent Selection: TiltText • Presented at UIST 2003 • Between-group selection: press key • Within-group selection: tilt phone • Actions performed concurrently • Suggests new area of research

  7. Taxonomy: Multiplexed Keypad • 1,2 not possible • 4 & 5 are regressive • 3 suggests a use for chording

  8. Mobile Chording • Chording input for mobile devices: • Selection tasks suggests better fit for chording on mobile phone

  9. ChordTap • Mobile phone selection tasks: • Between group selection (phone keypad) • Within group selection (chord keys) • Performed concurrently

  10. Design Issues • Mapping chord states to within-group selection • Event that triggers text generation

  11. Chord Mappings • Ignoring case, buttons have 4 or 5 characters • Each chord has 2 states (down=0, up=1) • log25 = 3, 3 chords needed

  12. Chord Mappings

  13. Character Generation Event • Issue: when is character generated? • Actions To Generate a Character: Depress keypad button Depress chord Key Release… which? 1. 2. 3.

  14. Why Does it Matter? • Non-event keys can be visualized • Reduces erroneous text entry • Helps with learning • Non-event key can be held for subsequent character, savings

  15. 9 W X Y Z Keypad Button Release (eg): 1. 2. Depress keypad button: Depress chord key: Screen: 3. Release keypad button – text is generated. If next character requires same chord, keep it held down to skip step 2.

  16. Work Savings • Subsequent characters with same chords:

  17. Keypad Button Release • Allows for visualization of within-group selection • Allows same chord to be held for successive characters • Savings on 20% of pairings

  18. … Screen: A D G J Chord Key Release (eg): 1. 2. Depress chord key: Depress keypad button: … 3. Release chord key – text is generated. If next character requires same chord, keep it held down to skip step 2.

  19. Work Savings • Subsequent characters with same keypad button:

  20. Chord-Key Release • Character generated when chord-key released • Allows for visualization of between-group selection • Allows same button to be held for successive characters • Savings on 9% of pairings

  21. Chord-Key or Keypad Button • Text generated every time any key released • Allows for no pre-visualization • Greatest savings: 29%

  22. Our Prototype • Button release text generation • Equipped with 3 chords • Implemented on Mot i95cl • Mouse board for chords • 2-handed

  23. The Study • Comparing ChordTap to MultiTap • Between-Subject Design: 15 participants 3 techniques (MultiTap: 1 or 2 handed, ChordTap) 16 blocks of 20 phrases each 2 sessions • Same phrases for both techniques • Measured time & accuracy • Participants told to correct mistakes

  24. Results: Overall Speed • End of experiment: MT1: 11.05, MT2: 12.04, CT: 16.06 Day 1 Day 2

  25. Power-Law Extrapolation

  26. Results: Error Rate Day 1 Day 2

  27. Conclusions • Identified taxonomy of research • Explored a new area within taxonomy • Fit chording to mobile-phone keypad: • Mappings • Text generation event • Implemented prototype • Formal study conducted • Chording better than MultiTap

  28. Future Work • Chording for one hand • Further exploration of taxonomy • Study of text generation event and mappings

  29. Acknowledgements • Tovi Grossman • Maya Przybylski • Krista Strickland • DGP Lab members • Study participants • Microsoft Research

  30. Thank You!

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