Apple Inc. v. Samsung Electronics Co. Ltd. et al
Declaration of BENJAMIN B. BEDERSON IN SUPPORT OF SAMSUNG'S OPPOSITION TO APPLE'S MOTION FOR PRELIMINARY INJUNCTION filed bySamsung Electronics America, Inc., Samsung Electronics Co. Ltd., Samsung Telecommunications America, LLC. (Attachments: #1 Exhibit A, #2 Exhibit B, #3 Exhibit C, #4 Exhibit D, #5 Exhibit E, #6 Exhibit F, #7 Exhibit G, #8 Exhibit H, #9 Exhibit I, #10 Exhibit J, #11 Exhibit K, #12 Exhibit L, #13 Exhibit M)(Maroulis, Victoria) (Filed on 8/22/2011) Modified on 8/29/2011 cannot link entry-opposition has not been efiled (dhm, COURT STAFF).
April 2–7 ׀Portland, Oregon, USA
PAPERS: Small Devices 1
AppLens and LaunchTile: Two Designs for One-Handed
Thumb Use on Small Devices
Amy K. Karlson, Benjamin B. Bederson
Human-Computer Interaction Lab
Computer Science Department
Univ. of Maryland, College Park, MD, 20742
One Microsoft Way, Redmond, WA 98052
output. These devices allow for single-handed interaction,
which provides users with the ability to place calls and
access information when one hand is otherwise occupied.
However, because smartphones lack a touch-sensitive
display, user interaction is constrained to a discrete set of
keys, and thus the options for interaction design are limited
to keypad-mapped functions and directional navigation.
Another design approach, typically classified as a “Personal
Digital Assistant” (PDA) features a touch-sensitive display
surface designed primarily to be used with an included
stylus. This design offers greater software design flexibility,
but many of the small targets designed for a stylus are too
small for fingertip actuation, making one-handed use
difficult or impossible.
We present two interfaces to support one-handed thumb use
for PDAs and cell phones. Both use Scalable User Interface
(ScUI) techniques to support multiple devices with different
resolutions and aspect ratios. The designs use variations of
zooming interface techniques to provide multiple views of
application data: AppLens uses tabular fisheye to access
nine applications, while LaunchTile uses pure zoom to
access thirty-six applications. We introduce two sets of
thumb gestures, each representing different philosophies for
one-handed interaction. We conducted two studies to
evaluate our designs. In the first study, we explored whether
users could learn and execute the AppLens gesture set with
minimal training. Participants performed more accurately
and efficiently using gestures for directional navigation
than using gestures for object interaction. In the second
study, we gathered user reactions to each interface, as well
as comparative preferences. With minimal exposure to each
design, most users favored AppLens’s tabular fisheye
Our goal is to create a new single-handed interaction
system for both smartphone and PDA devices. In this work,
we have focused on the problem navigating device
applications, and have adopted two design strategies. The
first leverages Scalable User Interface (ScUI) techniques
[2,3] to allow the system to adapt to different screen
resolutions as well as support both portrait and landscape
device rotation. This architecture allows developers to
create a single application that can target a wide variety of
screen resolutions, and provides users with a consistent
interface and interaction model across devices. We
accomplish this using the University of Maryland’s
Piccolo.NET development toolkit for zoomable and
scalable user interfaces [5,18].
One-handed, mobile devices, gestures, notification, Piccolo,
thumb navigation, Zoomable User Interfaces (ZUIs).
ACM Classification Keywords
H.5.2. User Interfaces: Input Devices and Strategies,
Interaction Styles, Screen Design; D.2.2 User Interfaces;
I.3.6 Interaction Techniques
Our second design strategy provides access to rich
notification information from multiple applications. Most
current PDA interfaces are designed for focused interaction
with a single task or application, with limited consideration
or display real estate allocated for notifications (e.g., email,
appointment reminders) or monitoring of ambient
information streams (e.g., stocks, sport scores). In our
proposed designs, each application has a dynamic launch
tile in the place of a static launch icon. This feature offers
high-value at-a-glace information for several applications at
once, as well as on-demand application launch when users
desire more detailed information.
The current generation of mobile computing hardware
features a variety of devices for interaction with the system
software. One such class of devices, typically referred to as
“smartphones”, features a numeric keypad or miniature
thumb keyboard for input together with a screen for display
Permission to make digital or hard copies of all or part of this work for
personal or classroom use is granted without fee provided that copies are
not made or distributed for profit or commercial advantage and that copies
bear this notice and the full citation on the first page. To copy otherwise,
or republish, to post on servers or to redistribute to lists, requires prior
specific permission and/or a fee.
CHI 2005, April 2–7, 2005, Portland, Oregon, USA.
Copyright 2005 ACM 1-58113-998-5/05/0004…$5.00.
In the work presented here, however, we limit our
discussion of scalability and notification in favor of
emphasizing the design features relevant to one-handed
April 2–7 ׀Portland, Oregon, USA
PAPERS: Small Devices 1
One handed device interaction has typically focused on text
entry techniques, but beyond a numeric keypad, most onehanded text entry systems require specialized hardware,
such as accelerometers [25,30] or customized keyboards
. We instead address the more general task of system
navigation and interaction, and restrict our designs to
interaction. We proceed by describing two designs:
AppLens (characterized by zoom+fisheye) and LaunchTile
(characterized by zoom+pan). The two approaches employ
variations of zooming interface techniques  to overview
several notification tiles, each roughly the size of a postage
stamp. AppLens uses a tabular fisheye approach to provide
integrated access to and notification for nine applications.
LaunchTile uses pure zooming within a landscape of thirtysix applications to accomplish the same goals.
Commercial products have also emerged with related
design goals. The Jackito PDA  supports thumb-only
interaction, but presumes two handed use and is not gesture
oriented. Lastly, Apple’s iPod is an elegant one-handed
interaction solution for audio play and storage , but is
currently not designed for the type of generalized
application interaction we propose.
Fisheye and pure zoomable techniques both offer promise,
but there are no clear guidelines as to when each approach
should be used. Our approach in this work, therefore, has
been to design and build the best interfaces we could with
roughly the same functionality, and then compare and
contrast the results. In this way, we hope to understand
which design direction makes the most sense for this
domain and to learn something about the trade-offs between
the two approaches.
THE ZOOM+FISHEYE APPROACH: APPLENS
AppLens provides one-handed access to nine applications,
and is strongly motivated by DateLens, a tabular fisheye
calendar . We refer to AppLens as a “shell” application
for its role in organizing and managing access to other
For device interaction when using a touch-sensitive screen,
both designs utilize a gestural system for navigation within
the application’s zoomspace. While our designs do not
directly address one-handed text entry, they are compatible
with a variety of existing single-handed text input
techniques, including single- and multi-tap alphanumeric
keypad input, as well as miniature thumb keyboards and
unistroke input systems executed with a thumb (e.g.,
Graffiti , Quikwriting ).
Generalized Data Access Using Tabular Fisheyes
Spence and Apperley  introduced the “bifocal display”
as one of the first examples of fisheye distortion applied to
computer interfaces. Furnas extended the bifocal display to
include cognitive perceptual strategies and introduced a set
of analytical functions to automatically compute
generalized fisheye effects . Since then, fisheye
distortion has been applied with mixed success across a
variety of domains, including graphs , networks ,
spreadsheets , and documents [12,23].
Gestures have proven a popular interaction alternative when
hardware alone fails to effectively support user tasks,
typical of many nontraditional devices, from mobile
computers to wall-sized displays . Gestures can be very
efficient, combining both command and operand in a single
motion, and are space-conserving, reducing the need for
software buttons and menus. However, the invisible nature
of gestures can make them hard to remember, and
recognition errors can negatively impact user satisfaction
. Recent research efforts pairing gestures with PDAsized devices have emphasized gestures based on changes
in device position or orientation [10,21,28]. However, our
work more closely resembles the onscreen gestures that
have played a prominent role in stylus-based mobile
computing (e.g., Power Browser ).
Bederson et al.  drew upon that work in developing
DateLens, a space-conserving calendar for PDAs, which
was shown to perform favorably for long-term scheduling
and planning tasks when compared to a traditional calendar
implementation. One of the strengths of DateLens was the
pairing of distortion and scalability, which allowed the
details of a single day to be viewed in the context of up to
several months of appointment data. Also important was the
design of effective representations for the variety of cell
sizes and aspect ratios that resulted from tabular distortion.
One drawback of DateLens, however, was that it required
two-handed stylus interaction to actuate the small interface
widgets. Our design extends the principles of DateLens to
include one-handed thumb access and generalizes the
approach for use across a variety of domains.
Our thumb-as-stylus designs support usage scenarios in
which only one hand is available for device operation, such
as talking on the phone or carrying a briefcase. Although
existing stylus-based gesture systems do not preclude the
use of the thumb, we are not aware of any systems that have
been specifically designed for the limited precision and
extent of the thumb. The EdgeWrite  gesture-based
stylus text entry system is particularly suited to mobile
usage scenarios due to its use of physical barriers.
EdgeWrite adaptation to one-handed mobile computing is
compelling, but would require expanding the dedicated
input area to accommodate thumb-resolution gestures.
We developed a scalable framework that provides a grid,
tabular layout, and default views for cell contents at a
variety of sizes and aspect ratios. We also developed a
general API to make it simple for applications to be built
within this framework; developers need only to replace a
small number of cell views with representations that are
meaningful within the target domain.
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PAPERS: Small Devices 1
tiles, may be rendered quite differently depending on their
position relative to the focus tile, which dictates whether the
peripheral tile is a square, a wide-flat rectangle, or a narrowtall rectangle. To reduce visual overload, peripheral tiles are
displayed at 40% transparency. The contents of distorted
peripheral tiles are not themselves distorted, but rather
change representation to provide the most meaning in the
The third and final Full zoom level expands a tile to a fully
interactive application that occupies 100% of the display
Gesture-Based Cursor Navigation
Existing application designs for PDAs are often inappropriate
for one-handed use due to their reliance on screen regions
that typically cannot be reached while maintaining control of
the device (e.g., accessing the Start menu in the upper lefthand corner of a display while holding the device in the right
hand), and the use of standard widgets that are too small for
reliable thumb use (e.g., radio buttons, checkboxes, and onscreen keyboards). In support of traditional designs, AppLens
uses an object cursor to identify the on-screen object that is
the current interaction target. The cursor is depicted as a
dynamically-sized rectangular orange border that users move
from one on-screen object to another via command gestures.
Cursors are not new to PDA interface design: the WebThumb
 web browser includes a similar notion of cursor, but
which is controlled via directional hardware, and others 
have explored device tilting to manipulate PDA cursors.
Neither the cursor nor gestures interfere with the most
common stylus interactions of tap and tap+hold. Although
gestures do overlap stylus drag commands, dragging is rarely
used in handheld applications and could be distinguished
from gestures by explicitly setting a gesture input mode.
Figure 1. AppLens Zoom Levels: (a) Notification, (b) Full,
(c, d) Context.
The AppLens shell (Figure 1) has been implemented within
our generalized tabular fisheye framework, using a 3x3
grid, and assigning one of nine applications to each cell.
The support for tabular layout includes representations at 3
zoom levels: Notification, Context and Full.
Notification zoom distributes the available screen real estate
equally among the 9 application tiles (Figure 1a). One tile
(shown centered) remains reserved for settings, which can
be used to configure the selection of applications which
occupy the other 8 notification tiles. Generally, tiles at
Notification size display high level static and/or dynamic
application-specific notification information.
We established a core set of commands that would allow
users to navigate applications using only the input cursor.
Our command language supports directional navigation (UP,
DOWN, LEFT, RIGHT) as well as two widget interaction
commands: one equivalent to a stylus tap (ACTIVATE), and
the other which negates widget activation (CANCEL),
equivalent to tapping the stylus outside the target widget. We
also include the convenience commands FORWARD and
BACKWARD, equivalent to TAB and SHIFT-TAB on Windows
AppLens Zoom Levels
Our use of gestures is motivated by Hirotaka’s observation
that the button positions on cell phones require interaction
using a low, unstable grip . PDA joysticks face a similar
drawback in that they are typically located along the lower
perimeter of the device. AppLens avoids this problem since
its gestures can be issued anywhere on the screen. Each
AppLens gesture is uniquely defined by a slope and
direction, or vector, which allows gestures to be robust and
highly personalizable; users can issue gestures of any length
(beyond an activation threshold of 20 pixels) anywhere on
Context zoom (Figure 1c) allocates roughly half the available
display area to a single focus tile, compressing the remaining
tiles according to a tabular fisheye distortion technique
[3,20]. A tile at Context size typically appears much like a
fully functional application, but selectively displays features
to accommodate display constraints, and is not interactive.
Tiles on the periphery of a Context zoom, called peripheral
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PAPERS: Small Devices 1
application tile to animate from Full zoom to Context zoom,
and if issued again, to Notification zoom.
the touch-sensitive surface. This flexibility lets users interact
with our designs using the grasp that provides maximum
stability in a mobile scenario.
Figure 2. Screen area
accessible with one hand.
Figure 3. The gesture set.
We based the gesture set on the limited motion range of
thumbs (Figure 2), with the goal of creating a gesture
language that could be learned with minimal training. After
informally experimenting with a variety of gestures, we
developed a simple set of gestures with the aim of
maximizing memorability and robustness of execution
(Figure 3). We assigned the directional commands UP, DOWN,
LEFT and RIGHT to spatial gestures that map directly to their
function. We assigned ACTIVATE and CANCEL to the two
gestures defined by pivoting the thumb from bottom to top
and top to bottom respectively. We made these assignments
both to reinforce their opposing relationship as well as for
ergonomic ease in issuing common commands. Finally, we
assigned the upper-left to lower-right diagonal to FORWARD
due to its relative forward nature, and by similar reasoning,
the reverse gesture to BACKWARD.
The eight gesture commands can also be activated with a
numeric keypad by mapping each to the key corresponding to
the gesture endpoint: 1-BACKWARD, 3-ACTIVATE, 7-CANCEL,
and 9-FORWARD. Since smartphones have a joystick that can
be used for directional navigation, the keypad-to-command
mapping is not necessary, but can be assigned as follows: 2UP, 4-LEFT, 6-RIGHT and 8-DOWN.
Figure 4. Three LaunchTile zoom levels: (a, b) Zone, (c)
World, (d) Application
THE ZOOM+PAN APPROACH: LAUNCHTILE
Our second design, LaunchTile proposes another way to
interact with a grid of notification tiles. The primary shell of
the LaunchTile design is an interactive zoomspace consisting
of 36 application tiles, divided into 9 zones of 4 tiles each
(Figure 4c). The 36 tile configuration is an exploration of the
maximum number of applications that can reasonably fit
within the display space. Since the design is fundamentally
scalable, however, it can display any number of tiles up to
36, and fewer may even be preferable. As a central design
element, LaunchTile uses a large blue onscreen button, called
Blue (Figure 4a), to unify the shell and applications with a
consistent visual metaphor. Blue provides a consistent point
of reference for zooming and panning navigation, with
onscreen tiles, menus, and functions maintaining a consistent
relative position to Blue. The LaunchTile zoomspace consists
of 3 zoom levels: World (36 tiles, Figure 4c), Zone (4 tiles,
Figures 4a and b) and Application (1 tile, Figure 4d).
Using Command Gestures within AppLens
Users navigate between AppLens zoom levels using
ACTIVATE and CANCEL gestures. As a rule, the ACTIVATE
gesture behaves as a stylus tap on the current cursor target,
thus its effects are target-specific. Since application tiles are
non-interactive at Notification and Context zoom levels, the
ACTIVATE gesture simply zooms in, animating the layout first
from Notification to Context zoom, and then to Full zoom.
Once at Full zoom, the input cursor transitions to the objects
within the application, at which point the command gestures
affect the current target widget. The CANCEL command
negates the effects of the ACTIVATE command. At Full zoom,
the effects of the CANCEL command depend on the location
of the cursor and the state of its target. The CANCEL
command will first deactivate an active target. If the current
target is not in an active state, CANCEL will cause the
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PAPERS: Small Devices 1
Zooming In to an Application
The Zone view of LaunchTile divides the screen area into 4
equally-sized application tiles (Figure 4a). To view other
tiles, the user pans the zoomspace to neighboring 4-tile
clusters, called zones. The zones are arranged as a 3x3 grid,
each associated with a numerical designator from 1 to 9 as on
a conventional telephone keypad. Zone 5 is the center zone,
which defines the Home screen, and shows the 4 highest
priority notification tiles, as configured by the user.
The user taps any of the 4 notification tiles within Zone view
to launch the corresponding application. An animated zoom
draws the zoomspace toward the user until the target
application fills the entire display (Figure 4d). If the device
has only a numeric keypad (no touchscreen), the user presses
the numeric key in the corner that corresponds to the zone.
Pressing 1 launches the upper left tile, 3 launches the upper
right, 7 launches the lower left, and 9 launches the lower
right. This technique provides quick, single-tap access to
each visible tile, and was inspired by ZoneZoom of Robbins
et al. .
To support various input hardware and styles of interaction,
there are several ways to pan the zoomspace within Zone
view. If the device has a multidirectional control joystick, the
user can push it in the direction of the targeted zone. From
the Home screen, the 16 tiles in zones 2, 4, 6, and 8 are only
a single tap away. As many directional pads do not support
diagonal action, the 16 additional tiles in the corner zones 1,
3, 7, and 9 are two taps away. Alternatively, if the device has
a touch-sensitive display, the user can use his or her thumb
directly to drag the zoomspace. Dragging is performed “on
rails”, permitting the user to drag vertically and horizontally,
but not diagonally. Although the zoomspace moves with the
thumb during dragging, Blue remains centered and
stationary. Because only one instance of Blue exists within
Zone view, each zone is depicted with an empty center hub
during dragging. Upon thumb release, the zoomspace
animates to align Blue with the closest zone’s empty hub.
The visual and automated guidance ensures the user is never
caught between zones.
As the system zooms, Blue stays in view and retains its
function as a central point of reference (Figure 4d).
Application menu commands are represented as on-screen
buttons clustered around Blue, now positioned at the bottom
of the display. Each menu button displays a numeric label, so
that mobile phone users may activate each menu by pressing
the corresponding number on the keypad. A visual indicator
to the left of the zoomspace animates during interaction to
reflect the user’s current absolute zoom level within the
Pressing Blue typically moves the user deeper into the object
hierarchy, while a dedicated Back button moves the user up
the hierarchy. In the Zone view however, Blue toggles
between Zone view (4 tiles) and World view (36 tiles). Once
an application is launched, three dedicated software buttons
along the top edge of the screen support inter- and intraapplication navigation (Figure 4d). A green Home button
immediately zooms the view out to the Home screen. There
is also a Back button on the upper right edge of the screen,
and another global command key. The placeholder for this
function in our prototype is an icon for voice command and
control. On a non-touchscreen device, Back and Home
commands are executed with dedicated physical buttons,
such as those provided on a smartphone.
Within each 4-tile zone, indicator widgets communicate the
user’s relative location within the zoomspace. The indicator
has two components. First, directional arrows show where
other zones are. If users only see indicators pointing up and
right, they know they are in zone 7. Small blue dots featured
with the arrows represent the location of all zones not
currently in view. The blue dots could also be used to
indicate an alert or status change in a neighboring zone,
though this feature was not implemented in our prototype.
The final way to pan the zoomspace is to tap the directional
indicator itself. An oversized hit target ensures that the user
can easily hit the indicator without using a stylus.
Although the original focus of our designs was on the
application “shell”, we extended the LaunchTile interaction
philosophy to the application level, where we sought to make
interaction consistent with navigation among the application
tiles. Several gestures have been designed to specifically
support one-handed navigation and item selection within
applications. Previously, others have demonstrated that for
direct-manipulation interfaces, a grounded tap-drag-selectrelease technique is more accurate than a tap-to-select .
We therefore made all LaunchTile tap-to-select targets large
enough for thumb activation. In cases when limited display
real estate necessitates smaller targets, the central Blue
widget serves as a moveable tool glass which can be
positioned over the target object (e.g., email header, message
text). The large thumb-friendly drag target is offset below the
selection area to prevent the user’s thumb from occluding the
target. Alternatively, the user can drag the application
Zooming Out to the World View
From any one of the nine 4-tile Zone view zones, the user
may tap Blue (or press the 5 key) to zoom out to view the
entire 36-tile zoomspace (Figure 4c). Since all 36 tiles are
visible at once, this view reduces each tile to a small icon.
From this World view, the user can easily see the absolute
location of each tile, as well as monitor all applications at
once. In the World view, the display is divided into a grid of
9 hit targets, each mapping to a 4-tile zone. Single-tapping a
zone animates to Zone view, displaying the zone’s 4
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map, or a list of email headers. In AppLens, gestures only
affect the cursor target, rather than the objects over which the
gesture is performed. The success of AppLens therefore
depends as much on the utility of the tabular design as the
ability for users to execute the gesture command set.
Participants were tested on gesture execution performance
and efficiency in navigating an information space.
contents, such as to pan a map, scroll a list of email, or
navigate to text outside the view area. Together, these two
interaction techniques permit the user to address a large
application content space, yet bring focus to a target much
smaller than a finger. Alternatively, a non-touchscreen user
uses the multidirectional joystick to position the selection
area on the screen. Keys 2 and 8 are used for page control up
and down, and 4 and 6 can be either menu items or horizontal
page control, as appropriate.
PARTICIPANTS: 20 participants (12 male, 8 female) were
recruited from the general population with the only selection
criteria being that participants were right-handed. The
median participant age was 30, and although 12 of the
participants considered themselves advanced computer users,
only 6 regularly used a PDA.
Once the targeted item is in the tool glass selection area, a tap
on Blue (or pressing the 5 key) activates the item, which may
either draw the user further into the application (e.g., open an
email), or may replace the application menus with a contextsensitive menu clustered immediately around Blue. As with
the application menus, keys on a numeric keypad execute
context menus according to their positions relative to Blue.
At this point a second tap on Blue sends the user to the
deepest level of the zoomspace, text input. At this level, a
modular text input object called an InputTile appears around
the selection area for alphanumeric input. Alternatively a
mini qwerty keyboard may be used for directly entering text.
With this design, a double tap on Blue while text is selected
will bypass the context menu and take the user directly into
text edit mode.
Figure 5. Example gesture study environment states: (a) the top
level, (b) the third level after ACTIVATE is performed on 6.5,
(c) highlighting within a cell.
The AppLens and LaunchTile prototypes have been built
using the University of Maryland’s PocketPiccolo.NET
development toolkit for Zoomable User Interfaces (ZUIs)
[5,18]. Although the primary development and test platform
has been the HP iPAQ PocketPC running Microsoft
Windows Mobile 2003, both run unmodified on the iMate
Smartphone II running Windows Mobile Smartphone 2003
(Figures 1d and 4b respectively).
MATERIALS: The study was run on an HP iPAQ measuring
4.5x2.8x0.5 inches with a 3.5 inch screen. We constructed a
software test environment modeled after AppLens: a
hierarchical tabular information space, with each level in the
hierarchy represented by a 3x3 grid of equal-sized cells,
numbered 1-9 like a phone keypad. For the experiment, the
hierarchy was limited to 5 levels and Context zoom was
eliminated so that activating a cell animated the display to the
next level. Cell contents served as navigational landmarks,
each labeled with a hierarchical address constructed by
prepending the cell’s local logical number (1-9) with its
parent’s label, separated by a dot (Figure 5b and 5c). We
reserved an area at the top of the screen for task instructions,
and disabled tapping to restrict input to gestures alone.
Gestures retained their meaning from AppLens: Navigational
gestures LEFT, RIGHT, UP and DOWN controlled the movement
of an orange rectangular cursor within a level; ACTIVATE
zoomed in to the next level and CANCEL zoomed out to the
previous level. Within the context of the test environment,
FORWARD and BACKWARD were used for intra-cell selection,
allowing participants to cycle a highlight either forward or
backward through cell label digits (Figure 5c). Highlighted
digits could then be bolded or “activated” using the
ACTIVATE gesture or un-bolded or “deactivated” using the
CANCEL gesture. Participants were provided with a reference
sheet that described the hierarchical information space and
labeling scheme, as well as the eight gestures to be used for
navigation and interaction.
Although the core architecture and gesture recognition for
each shell has been implemented, applications have been
simulated with images. This has allowed us to put designs
that are faithful to the look and feel of each shell in the hands
of users for early feedback, but falls short of full interactivity.
However, because LaunchTile design principles extend to the
applications themselves, we have prototyped email and
mapping as two interactive examples within LaunchTile.
We conducted two studies to inform future research
directions. The first study explored whether users could learn
and perform the AppLens gesture set with only minimal
training. The second was a formative evaluation which
gathered user reactions to each shell design, as well as users’
APPLENS GESTURE STUDY
A significant difference between the gesture designs of each
shell is that all gestures in LaunchTile are direct
manipulation, while all gestures in AppLens are remotecontrol commands. In LaunchTile, users physically drag
objects with their thumbs, be it the zoomspace, a tool glass, a
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flipping and answer-searching have been reflected in the task
time, and thus did not analyze this data further.
TASKS: Participants performed two types of tasks. Gesture
tasks required users to perform a gesture when presented
with the associated command name. Navigation tasks
required participants to navigate to a particular cell in the
hierarchy, and/or to activate or deactivate a cell label digit.
Number of Gestures
MEASURES: Application logs recorded task time, the
gestures performed for each task, and whether the task was
completed successfully. Participants were instructed to press
a hardware button between tasks, which served to record task
time and advance to the next task. Due to a bug in our
logging software, task time was recorded at second rather
than millisecond resolution. However, since our goal was to
identify performance trends rather than comparison to
another input method, one second resolution was sufficient.
Participants rated their experience using five nine-point
Likert scales: frustrating − satisfying, hard to learn – easy to
learn, hard to use – easy to use, slow – fast, and boring – fun.
Figure 6. Average number of gestures per task, by performance
tier, compared with the optimal.
The second test phase evaluated accuracy and efficiency for
goal-directed navigation tasks. The average task success rate
was 95%. While both navigation and navigation+activation
tasks were performed with 98% accuracy, activation was
close behind at 96%. Cancellation tasks, however, were only
completed correctly 83% of the time. On average,
participants performed 2.4 additional steps than the optimal
number to complete a task. Breaking participants into three
performance groups for each task, it is clear that one third of
participants performed nearly optimally on all but a few tasks
(Figure 6). The Middle third of participants performed
comparably to the Top third, but the gaps were wider on the
tasks the Top third had trouble with. That is, the tasks for
which the Middle third deviated farthest from Optimal, were
those for which the Top-tier also deviated. Thus, the most
significant difficulties in performing the navigation phase
tasks were experienced by only a third of the participants.
PROCEDURE: After reading a description of the test
environment and gestures, participants performed 16 practice
tasks similar in nature to those in the navigation task phase.
Participants practiced for 5-10 minutes.
After the practice phase, participants performed gesture
tasks: presented with a command name, participants
performed the associated gesture and pressed a hardware
button to advance to the next task. Command names were
presented to participants in random order, four times for each
of the eight commands. The gesture reference sheet was
placed face down so that the administrator could record the
number of times it was referred to.
The second test phase required participants to perform goaldirected tasks within the information space. These included
(N)avigation (“Navigate to 6.5.4”), (A)ctivation (“Activate
the 5 in 6.5.4”), (NA)vigation+activation (“Activate the 2 in
4.3.2”), and (C)ancellation (“De-activate all digits in 4.3.2”)
tasks. Participants then recorded their subjective ratings of
the interaction experience. Some participants completed the
study in as little as 15 minutes, most within 30 minutes, and
none required more than 40 minutes.
The average subjective rating for each of our 5 satisfaction
measures, on a scale of 1-9 where 9 was positive, fell within
a 1 point span of one another, between 5.9 (satisfying) and
Because the gesture phase of the study did not distinguish
between errors of recall and execution, we could not classify
the reasons for error. Analyzing the log files, it is safe to say
that errors of both types occurred. The low error and speed
measures for directional navigation support our hypothesis
that the directional gestures have an intrinsic spatial mapping.
Presumably, this mapping contributes to better learnability,
more reliable execution, and lower cognitive demand. The
positive jump in execution speed for the other four gestures is
unsurprising when we consider that the mappings between
gesture and command are more abstract than the directional
mappings, and likely require more cognitive effort to perform
the mental transformation. This alone does not explain the
associated increase in error rate, but insights from Long’s
work on gesture similarity  suggest that users may
perceive the diagonal gestures as similar and therefore more
difficult to learn.
In the gesture phase of the study, participants correctly
performed gestures an average of 87% of the time. By
gesture type, participants correctly performed directional
gestures 93% of the time, but had more difficulty with
diagonal gestures ACTIVATE and CANCEL at 88% and 85%
respectively. BACKWARD and FORWARD had the worst
success rate, at 70% and 64% of the time respectively. Time
to perform gestures followed a similar trend. On average,
participants required 2.4 seconds to perform each gesture: 1.5
– 1.7 seconds for directional gestures, 2.6 – 2.8 seconds for
ACTIVATE and CANCEL gestures, and 3.6 – 3.7 seconds for
BACKWARD and FORWARD gestures respectively. Neither
measure correlated with computer or PDA experience.
Although we tallied the number of times that participants
looked at a reference sheet, we assumed that the acts of page-
April 2–7 ׀Portland, Oregon, USA
PAPERS: Small Devices 1
questions. We limited each user session to 45 minutes,
allotting roughly fifteen minutes to each interface, and the
final fifteen for comparative feedback.
The difference in performance data between ACTIVATE and
CANCEL vs. BACKWARD and FORWARD may be attributed to
the more physically challenging nature of the latter two, but
may also be due to disproportionate practice time received,
considering a single navigation task provided more
opportunities to issue ACTIVATE and CANCEL gestures than
intra-cell activation tasks provided for FORWARD and
BACKWARD. These intuitions also help explain the efficiency
results – users were more successful and efficient in pure
navigation tasks which contained a proportionally large
number of directional gestures compared with intra-cell
activation/cancellation tasks. The relative complexity of the
gesture navigation environment may have confounded the
results by inflating the efficiency measures, but we feel that it
also made the results more relevant to the AppLens design.
Reactions to AppLens were quite consistent across
participants. Because only one question in the study focused
on a specific interface design feature (Context view), we
regard commonality in participant responses indicative of the
highest-impact interface characteristics. We report here on
the strongest trends in opinion. Half the participants
commented that they liked the Notification view and the
ability to access all nine application tiles within both
Notification and Context views. Even though two participants
found nothing redeeming about Context view, all others
found it useful at least some of the time. Seven participants
found application navigation easy and enjoyable, but
performed the majority of navigation using tapping rather
than gestures. Even so, participants were required to use
gestures to zoom out from Full zoom, and two participants
particularly liked the gestures. Five participants agreed that
the gestures were the most difficult aspect of the interface,
but disagreed on why, citing confusion over the gestures for
zoom-in vs. zoom-out, difficulty performing the ACTIVATE
gesture, difficulty with directional navigation, and frustration
due to misrecognition. All participants found AppLens both
easy to learn and effective for navigating among applications,
all but one found one-handed use comfortable, and six out of
seven participants stated they would prefer AppLens over
their most familiar PDA operating system.
APPLENS AND LAUNCHTILE FORMATIVE STUDY
Due to the early nature of our interfaces, their shared design
principles, and our goal of distilling a unified design, we
conducted a formative study to understand usability issues
for new users of each shell design and to elicit general
reactions and comparative preferences.
PARTICIPANTS: We recruited ten participants (8 male, 2
female) from a local private scientific research center. Three
participants were in their 20s, five in their 30s, and two were
40 or older. While all participants considered themselves
advanced computer users, four used PDAs regularly, and
four had never used a PDA.
MEASURES: Participants provided subjective designspecific and comparative reactions to AppLens and
LaunchTile through think aloud and verbal questionnaires.
Perhaps due to the richness of the LaunchTile environment,
reactions were mixed and more complex. Nearly half the
participants reacted positively to the aesthetics of
LaunchTile, and specifically to Blue. Seven participants
appreciated the volume of information available through the
two zoom perspectives World and Zone, while six thought
that zooming between those perspectives was one of the
easiest aspects of the interface. The majority (7) of
participants felt comfortable using one hand to perform the
tasks, and eight felt they were able to effectively navigate
among applications, primarily by tapping via World view.
MATERIALS: The shell prototypes were run on the same
hardware used in the first study. A one-page document
described the AppLens design and gestures set, followed by a
list of eight associated tasks. A two-page document described
the LaunchTile design and methods for navigation and
interaction, followed by a list of 11 tasks.
TASKS: For each interface, participants performed tasks
which were designed to exercise the full range of navigation
and interaction features. For example, LaunchTile tasks
included navigating to specific zones, finding specific
applications, and opening and editing an email message.
AppLens tasks included navigating to specific application
tiles, and answering questions about application content.
Surprisingly, a majority (7) of participants had difficulty
panning by dragging within LaunchTile, commenting most
often that it was unintuitive, but also that it was slow. This
subset of participants was slightly skewed toward
participants who used the LaunchTile interface first, and thus
would not have been biased by experience with the AppLens
directional gestures. Six participants struggled with the multimodal nature of Blue, unsure about its role in different
contexts, especially within applications. A related problem
was that of differentiating between the roles of the Home,
Back, and Blue buttons from within an application. Most of
the participants were tentative and had difficulty performing
tasks within the email application. Ultimately, participants
were evenly divided (3 vs. 3) about whether they would
PROCEDURE: Study participants were introduced to each
design by reading its design document and performing each
of the related tasks. During the tasks, the test administrator
recorded think aloud reactions and usability observations.
After task completion, the administrator recorded answers to
open-ended questions related to the interaction, such as likes
and dislikes, features that were easy or hard to use or learn,
and comfort level. The same procedure was repeated for the
second interface. The administrator balanced the order of the
interfaces among participants. After interacting with both
interfaces, participants were asked comparative preference
April 2–7 ׀Portland, Oregon, USA
PAPERS: Small Devices 1
clearly 15 minutes is not sufficient for users to become
proficient with the variety of interaction techniques supported
by the interface.
choose to use LaunchTile for their own application
management - half as many as chose AppLens.
Comparing the two interfaces, most participants recognized
the trade off between the number of applications that could
be viewed at once and the amount of information conveyed
for each, yet seven out of nine participants thought AppLens
provided better at-a-glance value. Although nearly half the
participants were reluctant to compare the speed of
information access between the two interfaces due to the
differing amounts of information available, seven out of nine
participants thought AppLens supported faster data access,
presumably due to a better balance between the number of
applications and the presentation space available for each.
Additionally, AppLens was considered easier to use (7 out of
9), and 8 out of 9 would prefer AppLens for use on their own
device. In response to our general question about the utility
of one-handed use, 7 participants thought one-handed
interaction would be useful at least some of the time, with 3
of those stating an a priori preference for one-handed use in
all situations. However 2 participants expressed that they
would never want to use a PDA with one hand, regardless of
the interface design.
In  Bederson hypothesizes that user satisfaction is related
to how well an interface supports “flow”, which correlates
inversely to the degree to which an interface gets in the way
of, or interrupts, user tasks. Blue is an example of a
LaunchTile feature that interrupts flow: it performs different
functions in different contexts, requiring users to keep track
of the system state to predict the outcome of tapping Blue.
This type of functional overloading is a well-known design
issue, but is commonly used nonetheless. For example, both
the Microsoft and Apple desktop media players use a single
button for both Play and Pause. Just as with LaunchTile,
these designs compromise simpler mappings in favor of a
visually simpler design. The difference, however, is that both
media players change the button icon to reflect the current
state (i.e., the function the button will perform when pressed)
so that users don’t have to remember the state or deduce the
state from less obvious cues. A similar adaptation for Blue
may reduce or even eliminate user confusion in the
Two notable themes emerged from the comparative study.
The first was the participants’ reluctance to use gestures.
Results from the first study suggested that directional
gestures can be learned quickly, yet for both interfaces, users
favored tapping targets over issuing gestures. While this
trend may simply be a training issue, it may also be an early
warning sign for the adoptability of overlay gesture systems those that share the same real estate as the interface objects
themselves. Second, a large number of users commented on
the perceived utility of the simultaneous display of highvalue content from multiple applications, bolstering our
intuition that flexible notification-based designs may provide
an effective balance between functionality and content within
the real estate constraints of handheld computing.
Based on our participants’ strong interest in one-handed PDA
use, and generally positive reactions to their interaction
experiences, we are convinced of the value of research in
one-handed designs, and believe notification plays an
important role in effective utilization of limited real estate.
We have less evidence of the utility of design scalability
beyond being an engineering convenience. Although we have
demonstrated the feasibility of transferring both interfaces to
smartphones, we do not know whether the designs support
smartphone usage scenarios. With respect to command
gestures, we are encouraged by the modest yet positively
skewed satisfaction ratings for gesture interaction as well as
what we consider very reasonable performance for both
directional gesture execution and navigation tasks. It’s clear,
however, that the introduction of two additional diagonal
gestures degrades performance and confuses users. We will
need to explore whether AppLens can be an effective
interface without these additional commands, or whether a
different mapping of commands to gestures or on-screen cues
can make the full set of gestures as reliable and learnable as
directional gestures seem to be. Finally, we anticipate that
extended usage studies with wider populations will unearth
more subtle usability issues. With refinement, we hope a
single design will emerge to provide a consistent, flexible
environment designed for single-handed use.
While AppLens appeared to be the preferred design, we must
take care in assigning reasons for the preference. First,
AppLens is a simpler design and a shallower prototype than
LaunchTile. Its appeal may have been that users felt
proficient and better able to manage 9 applications (versus
36) with minimal use. Its simplicity also made AppLens less
prone to the performance limitations of the target hardware,
which noticeably impacted LaunchTile zooming quality.
However, more experience with the two designs might have
tipped the scales the other way, as Bederson has pointed out
in  that even complex interfaces have the potential to be
highly satisfying after users have expended the effort to
become experts. A vocal minority of expert PDA users who
much preferred LaunchTile supported this possibility, citing
the large number of applications and configurable layout as
very attractive features. Thus a different participant
population may have offered different opinions. While we do
not consider LaunchTile in this class of expert interface,
We appreciate François Guimbretière’s early suggestion of
considering the ergonomics of human thumbs, and thank
Aaron Clamage for his rapid efforts in porting Piccolo.NET
to small devices so we could build these prototypes.
April 2–7 ׀Portland, Oregon, USA
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