Ken Hinckley

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Quantitative Analysis of Scrolling Techniques

• Ken Hinckley
• Edward Cutrell
• Steve Bathiche
• Tim Muss
• Microsoft Research Microsoft Hardware
• April 23, 2002

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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?

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Accelerated Scrolling Wheel

• Scroll further when you roll faster
• Extend range of wheel
• But Is it really any better?
• Possible loss of control / precision?

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Motivating Questions Research

• How should one experimentally evaluate scrolling
  performance? Distance Precision?
• Which is fastest blue or green (dotted) ?

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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

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Scrolling Experimentfounded in Fitts Law

• Scroll back forth between 2 lines in a doc
• Ex comparing paragraphs
• Each Trial had at least 10 Phases of individual
  scrolling movements

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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 Ws
• e.g. D6, W18

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Note on Practice Effects

• First 2 phases of each trial eliminated due to
  start-up effects

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Results Average Movement Times

• Overall average Movement Time (MT)
• ScrollPoint Std. Wheel do not differ
  significantly
• But what if we control for D/W ?

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Results By Distance (Raw Data)

• Hard to see whats going on in raw MT data
• D 3.5 cm to 2.25 meters So MT also has wide
  range

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Results By Distance (Scaled)

• Significant crossover interaction by Distance!
• Std Wheel faster at small D, ScrollPoint for
  large D
• Accel mappings improve performance

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Results By Width

• No interesting crossover effects for Device X W
• A faster device is faster across all W

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and Fitts Law Describes our Data

• r 0.90 for all devices

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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

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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?

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Qualitative Results

• ScrollPoint Most Ss preferred for long D
• But in practice many would just grab scrollbar
• very ineffective in targeting lines
• my hand didnt 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

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Naturally Occurring Behaviors with the Wheel

• How do users roll the wheel?
• (1) trying to get somewhere fast, or
• (2) reading

fast
reading
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How Acceleration Works

• Roll faster ? move further
• But do not change reading experience
• For ?t lt 0.1 notch/s
• ?y K1(1 K2?t)a
• Otherwise
• ?y 1 line
• The user does nothave to learn anything new!

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ProductVersion

• To play with Accel. Scrolling, download
  IntelliPoint 4.0
• Differs slightly
• e.g. no fractional lines
• http//www.microsoft.com/ hardware/mouse/downloa
  d.asp

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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 expts needed with Fitts Law

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Thank You!

• Questions?
• kenh_at_microsoft.com
• http//www.microsoft.com/ hardware/mouse/download
  .asp

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(No Transcript)
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Extra slides for questions etc.
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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

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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.

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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)
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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

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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

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? OVERDRIVE

• 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