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Ken Hinckley Edward Cutrell Steve Bathiche Tim Muss Microsoft Research & Microsoft Hardware April 23, 2002. Quantitative Analysis of Scrolling Techniques. Motivating Questions: Product. Multi-Channel scrolling devices (1) save time to grab scrollbar

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Quantitative Analysis of Scrolling Techniques

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quantitative analysis of scrolling techniques
Ken Hinckley

Edward Cutrell

Steve Bathiche

Tim Muss

Microsoft Research & Microsoft Hardware

April 23, 2002

Quantitative Analysis of Scrolling Techniques
motivating questions product
Motivating Questions: Product
  • Multi-Channel scrolling devices

(1) save time to grab scrollbar

(2) maintain visual focus on primary task

  • Can performance of the scrolling wheel be improved?
    • How does it compare?
    • How to evaluate & test our new scrolling products in general?
accelerated scrolling wheel
Accelerated Scrolling Wheel
  • Scroll further when you roll faster
    • Extend range of wheel
  • But… Is it really any better?
  • Possible loss of control / precision?
motivating questions research
Motivating Questions: Research
  • How should one experimentally evaluate scrolling performance? Distance & Precision?
  • Which is fastest: blue or green (dotted) ?
fitts law cough syrup for input devices



Fitts’ Law: Cough Syrup for Input Devices
  • Widely used to study rapid, aimed movements (Fitts 1954)
  • Used in pointing device studies since 1978
  • Task: Point at a target W wide at distance D
  • The Law:
    • MT = a + b log2(D/W + 1)
    • a, b fit by linear regression using observed MT
  • Never applied to scrolling
scrolling experiment founded in fitts law


Target line

Scrolling Experimentfounded in Fitts’ Law
  • Scroll back & forth between 2 lines in a doc
    • Ex: comparing paragraphs
  • EachTrial had at least 10 Phasesof individual scrolling movements
experimental design
Experimental Design
  • Device X D X W
    • ScrollPoint
    • Standard Wheel
      • 3 lines/notch
    • Accel. W1
      • 1 line/notch
    • Accel. W3
      • 3 lines/notch
  • nonsensical D X W’s
    • e.g. D=6, W=18
note on practice effects
Note on Practice Effects
  • First 2 phases of each trial eliminated due to start-up effects
results average movement times
Results: Average Movement Times
  • Overall average Movement Time (MT)
  • ScrollPoint & Std. Wheel do not differ significantly
  • But what if we control for D/W ?
results by distance raw data
Results: By Distance (Raw Data)
  • Hard to see what’s going on in raw MT data
    • D: 3.5 cm to 2.25 meters; So MT also has wide range
results by distance scaled
Results: By Distance (Scaled)
  • Significant crossover interaction by Distance!
  • Std Wheel faster at small D, ScrollPoint for large D
  • Accel mappings improve performance
results by width
Results: By Width
  • No interesting crossover effects for Device X W
    • A faster device is faster across all W
and fitts law describes our data
… and Fitts’ Law Describes our Data
  • r ≥ 0.90 for all devices
representative tasks for scrolling
Representative Tasks for Scrolling
  • We experimented with several tasks:
    • Scrolling while proofreading text for misspellings
    • Searching for highlighted line in document
      • [and following the link – Zhai]
    • Searching for highlighted target word in document, in presence of highlighted distracter words
  • Fitts’ task sensitive to subtle device diffs
  • Cognitive & visual search issues ignored
design insights
Design Insights
  • No one device or acceleration setting is “best”
  • Accel W1 vs. Std Wheel: faster + better resolution
  • Is it possible to combine Accel W1 / Accel W3 mappings to have optimal performance?
qualitative results
Qualitative Results
  • ScrollPoint: Most Ss preferred for long D
    • But in practice many would “just grab scrollbar”
    • “very ineffective in targeting lines”
    • “my hand didn’t get tired”
  • Standard Wheel: moved predictably
    • Fatigue / comfort frequent negative comment
  • Accel W3: “very easy to scroll long distances”, but most Ss disliked larger notches
  • Accel W1: liked finer notches, but still “tedious to scroll long distances”
naturally occurring behaviors with the wheel
Naturally Occurring Behaviors with the Wheel
  • How do users roll the wheel?
    • (1) trying to get somewhere fast, or
    • (2) reading



how acceleration works
How Acceleration Works
  • Roll faster  move further
  • But do not change “reading” experience
  • For Δt < 0.1 notch/s

Δy =K1(1+K2Δt)α

  • Otherwise

Δy = 1 line

  • The user does nothave to learn anything new!
product version
  • To play with Accel. Scrolling, download IntelliPoint 4.0
  • Differs slightly
    • e.g. no fractional lines
  • http://www.microsoft.com/ hardware/mouse/download.asp
future work
Future Work
  • Apply Fitts approach to a scroll/select task
    • Scroll, then click on object of varying W
    • Two-handed scrolling: Current experiment can compare right- vs. left-handed devices, but not higher level benefits of 2h scrolling, e.g.
      • Anticipatory cursor motion
      • Avoid fatigue from single hand doing everything
    • Scrollbar: cost of moving mouse back and forth to scrollbar needs to be considered
  • More scrolling expt’s needed with Fitts’ Law
thank you
Thank You!
  • Questions?
  • kenh@microsoft.com
  • http://www.microsoft.com/ hardware/mouse/download.asp
jellinek card 1991
Jellinek & Card 1991
  • Gain theoretically does not affect performance
      • MT = a + b log2(D/W + 1); gD/gW = D/W
  • Observed MT almost unchanged for g = 1  10
  • g Reduces footprint of device & reclutching
  • On Wheel, reduced footprint = faster MT
principles of bimanual action
Principles of Bimanual Action
  • Yves Guiard, 1987. For right-handers:
  • Right-to-left reference: Action of the right hand occurs within the frame-of-reference defined by the left.
  • Scale Asymmetry: Movements of the right hand occur at higher spatial and temporal frequencies than the left
  • Left-hand Precedence: Action starts with the left hand.
principles of bimanual scrolling
Principles of (Bimanual) Scrolling
  • Scrolling is a background task that should be assigned to the nonpreferred hand.
  • Right-to-left reference: Movement of mouse cursor is within current document view.
  • Scale Asymmetry: Scrolling is a coarse task, cursor movement & selection are high-precision
  • Left-hand Precedence: Scrolling precedes detailed activity in the document.

(MacKenzie 1998)

bimanual scrolling
No switching between pointing & scrolling

Overlapped action of the 2 hands

Maintain visual focus & concentration on work

Buxton & Myers 1986bimanual scrolling ~25% faster than scroll bar

Bimanual Scrolling
bimanual control on office kbd
Bimanual Controlon Office Kbd
  • Navigation controls on left
    • Scrolling [wide wheel]
    • Web [Forward / Back]
    • Windows [AppToggle]
  • Cut, Copy, Paste also well suited to left side
    • Compound selection [or placement of IP] + articulation of command
  • “Automatic transmission” for the wheel (+accel.)
  • Evaluating… Informally, seems to work great!
  • in a ~10 pg doc:

IntelliPoint 4.0! 

IP 5.0 (?) 

  • All of these have 1 line/notch precision