BEHAVIOUR & INFORMATION TECHNOLOGY, JANUARY–FEBRUARY 2004, VOL. 23, NO. 1, 1–9
`
`SlideBar: Analysis of a linear input device
`
`LESLIE E. CHIPMAN, BENJAMIN B. BEDERSON and JENNIFER A. GOLBECK
`
`Department of Computer Science, Human-Computer Interaction Laboratory, University of Maryland,
`College Park, Maryland, USA; e-mail: {gchipman, bederson, golbeck}@cs.umd.edu
`
`Abstract. The SlideBar is a physical linear input device for
`absolute position control of 18 of freedom, consisting of a
`physical slider with a graspable knob positioned near or
`attached to the keyboard. Its range of motion is directly
`mapped to a one dimensional input widget such as a scrollbar.
`The SlideBar provides absolute position control
`in one
`dimension, is usable in the non-dominant hand in conjunction
`with a pointing device, and offers constrained passive haptic
`feedback. These characteristics make the device appropriate for
`the common class of tasks characterized by one-dimensional
`input and constrained range of operation. An empirical study
`of three devices (SlideBar, mouse controlled scrollbar, and
`mousewheel) shows that for common scrolling tasks, the
`SlideBar has a significant advantage over a standard mouse
`controlled scrollbar in user preference. In addition, users
`tended to prefer it over the mousewheel (without statistical
`significance).
`
`1. Background
`
`Personal computers have come to be so popular
`largely because they are multi-function devices. They
`consist of general-purpose processors, general-purpose
`input devices, and general-purpose output devices. This
`is a fundamental design feature of today’s personal
`computers, and it works remarkably well. However, this
`design represents one side of a trade-off that results in a
`computer that can do many tasks well, but does not
`necessarily do each individual
`task as well as a
`specialized device could. Certain very common tasks,
`such as scrolling, are a case in point. It is no surprise
`then, that design,
`implementation and evaluation of
`scrolling mechanisms and pointing devices are well-
`studied areas.
`In traditional graphical user interfaces (GUIs), a
`document such as a spreadsheet, text file, or file list in a
`folder is often larger than the viewing window. Thus, the
`user views only part of the document at a time. To view
`portions of the document outside the viewing window,
`
`one must move the window relative to the document.
`Scrolling behaviour is an extremely frequent task in
`GUIs, and it becomes even more frequent in browsing
`World Wide Web pages.
`Scrolling is just one example of a common class of
`computer input
`tasks characterized by having one
`dimension of
`freedom and a constrained range of
`operation. Some other examples are selecting from
`menus, zooming in and out of documents and operating
`onscreen widgets, e.g., slider widgets. Even if there is not
`an explicit mouse controlled widget, the task can still
`exist and in current applications is often controlled via
`keyboard or with specific selections from menu items.
`For instance, photo browsing applications commonly
`have a menu for controlling the magnification with
`common values such as 50, 100 or 200%, or in specific
`modes,
`the user may increment or decrement at
`predefined values with a mouse click, giving limited
`control of a task that actually has a smooth, broad
`range of input values.
`Since this common class of tasks is broad and well
`defined, it seems logical to consider an input device
`tailored specifically for this purpose. In this paper, we
`introduce the SlideBar, a linear input device for absolute
`position control, which we built with the goal of
`providing users with an input device better suited for
`linear tasks. In this paper, we delve into the reasons we
`expect this device to be well suited for linear tasks and
`give the results of a study comparing it to common input
`devices for the specific linear task of scrolling.
`As computer users, we have become accustomed to
`using the standard mouse and keyboard as input devices
`and so it may be difficult to recognize some of their
`inherent drawbacks. There is more willingness
`to
`incorporate new devices into the interface, especially
`with the increasing popularity of
`laptop and even
`smaller computers where the limitations of a mouse
`become more pronounced. We believe the SlideBar
`
`Behaviour & Information Technology
`ISSN 0144-929X print/ISSN 1362-3001 online # 2004 Taylor & Francis Ltd
`http://www.tandf.co.uk/journals
`DOI: 10.1080/01449290310001638487
`
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`L. E. Chipman et al.
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`offers a large enough advantage to justify being built in
`to some computers.
`
`1.1. Scrolling
`
`We have observed that users scroll primarily in two
`modalities. The first modality is to read a document,
`where the document is slowly scrolled a few lines at a
`time so that the user can easily track the line being read.
`We will refer to this as read mode. The second modality
`is to scan a document, typically when a user is searching
`the document to find a specific part of it. In this mode,
`the user typically scrolls the document back and forth
`through large areas. We will refer to this as scan mode.
`After the specific area sought for is found, the user
`typically switches to read mode, and reads the document
`line by line.
`
`1.2. Scrolling mechanisms
`
`The most basic scrolling mechanism is the standard
`scrollbar controlled by a mouse. Other common
`methods include the mousewheel, keyboard, touchpad
`or joystick.
`
`1.2.1. The scrollbar:
`A scrollbar is an on-screen
`widget that the user controls with a general pointing
`device, such as a mouse,
`joystick, or touchpad. It
`supports absolute motion by acquiring and dragging
`the movable ‘thumb’, which allows the user to scroll
`through the document
`to any given position in a
`simple motion,
`independent of the document length.
`This is most appropriate for scan mode and the
`thumb provides lower resolution control for longer
`documents. Scrollbars also support relative motion by
`clicking on the arrows at the ends of the scrollbar to
`scroll one line at a time, or on the remaining space
`between the arrows and the handle, which scrolls
`several
`lines at a time. This is appropriate for read
`mode.
`The scrollbar appears to be an excellent control
`mechanism for scrolling since it provides support for
`relative and absolute motion and for both modalities of
`use. Of course, it does work well, and we all use it
`regularly. However, scrollbars do have several short-
`comings. The primary one results from the fact that
`users must use a general-purpose pointing device to
`control it. Each movement of the user’s hand between
`the keyboard and the mouse takes time. A study by
`Douglas and Mithal found it takes 0.67 s for users to
`acquire a mouse and 0.44 s for a keyboard joystick
`(Dougland et al. 1994). We would expect a time
`
`somewhere in this range for acquiring a keyboard
`mounted SlideBar.
`Even if the user’s hand is already on the mouse, the
`user must then move the pointer on the screen to the
`appropriate part of
`the scrollbar. Since common
`scrollbars are only about 15 pixels wide, acquiring the
`scrollbar takes up to two seconds (Zhai et al. 1997), and
`impacts performance,
`in accordance with Fitts’ Law
`(Fitts and Peterson 1954). Another shortcoming of
`scrollbars is that the user must take his or her eyes off
`the document and focus on the scrollbar to know where
`they are in the document.
`Finally, for ongoing scrolling tasks that last a long
`time, the user must hold down the mouse button for the
`full length of the scrolling task (if using the thumb), or
`regularly click (if using the trough or arrows). For users
`with Repetitive Stress Injury (RSI), this continuous
`force required of the fingers can be destructive.
`These actions are in conflict several common goals of
`good user interfaces: unobtrusiveness, transparency and
`ease of use. A good interface diverts a minimal amount
`of the user’s attention and effort away from the primary
`task of viewing a document
`in order to explicitly
`manipulate GUI widgets.
`
`1.2.2. The mousewheel:
`A mousewheel is commonly
`built into mice. It is a wheel between the two primary
`input buttons, which can be mapped to control the
`scrollbar with relative motion. It can be used to scroll a
`document a small amount with a corresponding wheel
`movement. For this reason, it supports read mode well.
`Because the range of motion is limited, the user must
`repetitively spin the wheel to scroll more than a few
`lines, making it ineffective for scan mode in all but the
`smallest documents.
`Some applications support rate scrolling with a
`mousewheel. With rate scrolling, the user presses and
`holds the mousewheel down,
`then the direction of
`movement of the mousewheel provides the direction of
`scrolling and the amount of displacement controls the
`rate of scrolling. In a comparison of various scrolling
`devices and mechanisms, Zhai et al. (1997) showed the
`performance of a mousewheel to be similar to that of the
`standard mouse. They also show rate scrolling to be
`more effective than standard scrolling when using an
`isometric joystick and indicate that the isometric nature
`of the device to be an important factor in rate scrolling.
`
`1.2.3. Arrow and page up/page down keys:
`Most
`keyboards have specialized keys for scrolling. The up
`and down arrow keys move the cursor up and down one
`line with a document. When the edge of the screen is
`reached, the document is scrolled. The Page Up and
`Page Down keys scroll several lines at a time. The actual
`
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`Analysis of a linear input device
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`3
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`is
`amount the Page Up and Page Down keys scroll
`specified by the application, but typically the document
`is scrolled some significant portion of the screen height.
`Though arrows keys are useful
`in read mode, they
`provide only relative control and so are very limited for
`use in scan mode. With the exception of specialized keys
`such as the ‘Home’ key, they provide no method for
`moving quickly to an absolute position in the document.
`
`1.2.4. Touchpad:
`Some laptops with touchpads can
`be used for controlling the scrollbar. Sliding the finger
`along the right edge of the touchpad provides relative
`control of the scrollbar. This supports read mode well. It
`is limited in scan mode by its relative nature, much as a
`mousewheel is, though constantly repositioning one’s
`finger on a touchpad may be less fatiguing that working
`a mousewheel over and over. It is possible to support
`rate scrolling with this input device, but as mentioned
`above, lack of isometric feedback is an issue.
`
`1.3. The slidebar
`
`The SlideBar is a physical linear input device that can
`be used to control absolute position of a 18 of freedom
`parameter
`(figure 1).
`It
`is
`intended primarily for
`scrolling, although it can also be used to control any
`other one-degree of freedom application. It is designed
`for non-dominant hand use, to be used in tandem with a
`mouse or other general-purpose pointing device in the
`dominant hand.
`Because the SlideBar is an absolute positioning
`device, the user can immediately move through the
`entire document, from top to bottom and through all
`
`the intermediate positions, although with limited resolu-
`tion. Because the document being scrolled has a top,
`bottom and a length, and the SlideBar has a top, bottom
`and a length, there is always a direct linear mapping
`between the SlideBar and the scrolled document.
`if a
`One issue with absolute positioning is that
`document is scrolled by a mechanism other than the
`SlideBar, the position of the SlideBar may no longer
`correspond to the viewing window of the document. The
`control software has been designed so that as soon as the
`SlideBar is moved at all, the document viewing windows
`jumps to the position that corresponds to the SlideBar.
`This is important since we hope that the prototype
`SlideBar can take advantage of the fact that it has a
`physical position in space, which allows users to develop
`awareness of what portion of the document they are
`viewing.
`
`1.4. Previous work
`
`Proprioception is the ability of people to sense the
`position and movement of their bodies, and has been
`studied for several decades. It has been shown that
`humans exhibit a remarkable ability to remember the
`position of their limbs (Boff et al. 1986). The SlideBar’s
`absolute linear mapping of document position should
`benefit from these effects.
`The use of haptic feedback in computer input devices
`is also a well-studied area. Passive haptic feedback refers
`to a mechanism where the user can control and feel the
`position of the input device but where there is no
`response or control from the computer, in contrast to
`force or active feedback. Note that this terminology
`
`Figure 1. The prototype slidebar.
`
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`4
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`L. E. Chipman et al.
`
`differs from that used in psychology where passive
`positioning means that ones body was moved externally
`by an apparatus and active refers to positioning done by
`voluntary muscle control. Fitzmaurice et al. (1995) and
`Fitzmaurice and Buxton (1997) showed the advantages
`of having more specialized, graspable input devices that
`operate via passive haptic feedback. Studies (MacKenzie
`1992, Lindeman et al. 1999, Wang and MacKenzie 2000)
`have also shown the importance of placing constraints
`on object movement for passive haptic feedback. The
`SlideBar should benefit from this as well since it is a
`constrained input device, physically moving only within
`the range of the task.
`User studies dealing with comparative analysis of
`input devices (Kabbash et al. 1993, 1994, Zhai et al.
`1997) have shown that given the chance to use both
`hands, people will naturally use the non-dominant hand
`for rough positioning and the dominant hand for fine
`positioning. To study two-handed input, Buxton and
`Myers (1986) used linear input devices in participants’
`non-dominant hand. For a scaling and positioning task,
`a physical
`linear slider with relative control for the
`scaling portion of the task was used. In a scrolling task,
`two touchpads were used for linear control. One gave
`absolute position control and the other gave relative
`control of the scrolling task. This gave users a different
`linear device corresponding to the different scrolling
`modes of scanning and reading. The SlideBar differs
`from these input devices in that only the SlideBar
`provides both absolute positioning and passive haptic
`feedback with physical constraints. Our purpose is to
`establish the benefit of the SlideBar, which is different
`from their purpose of studying the effect of two-handed
`input. We do expect two-handed input to be one of the
`SlideBar’s advantages and their study establishes this
`effect.
`two handed input, absolute
`The combination of
`positioning and constrained passive haptic feedback
`makes the SlideBar a unique computer input device
`for 18 of freedom tasks, which we believe it will excel
`at.
`
`2. Implementation of the Slidebar
`
`The current implementation of the SlideBar is a proof
`of concept prototype that consists of a linear potenti-
`ometer that is wired to generate an analog voltage as the
`potentiometer is moved. A graspable knob is attached to
`the potentiometer and it is placed to the side of the
`keyboard. The SlideBar has a range of motion of
`4.5 cm, which is designed so that moving just the wrist
`and fingers without moving the forearm can access the
`full
`range. The analog voltage generated by the
`
`potentiometer is then digitized through a 12-bit A-D
`converter.
`We wrote driver software to continuously read the
`SlideBar position via the serial port and generate events
`that are applied to scrolling. Position data for small
`changes is averaged, allowing for smoother control at
`slow scrolling rates, yet immediately applied for large
`position changes, maintaining the SlideBar’s ability to
`move anywhere within a document without delay. The
`amount of averaging applied varies and is inversely
`proportional to the position change (up to a limit), so
`that the averaging used does not suddenly change at an
`arbitrary boundary. We also wrote custom applications
`that listen to SlideBar events and control scrolling
`within those applications.
`The A-D converter limits the resolution of this version
`of the SlideBar to 4096 positions. As a comparison,
`scrollbars controlled by a mouse are limited in resolu-
`tion to one pixel, determined by the resolution of the
`screen. Every time the scrollbar moves one pixel, the
`document scrolls a corresponding amount. For a high-
`resolution display of 1024 vertical pixels, a mouse
`controlled scrollbar provides one-fourth the resolution
`provided by the SlideBar prototype. With the same pixel
`resolution, a 40-page document and a 10-point font, the
`SlideBar prototype resolution is about one line of text.
`However, the resolution of human movement may
`easily be less than that of the SlideBar. Numerous
`studies in joint proprioception show error to usually
`only a few degrees (Boff et al. 1986) and that the finger
`usually has higher error than other joints (Balakrishnan
`and MacKenzie 1997). But studies of finger position are
`finger alone, not finger and thumb grasping an object
`and references hint at this potential cause of inferior
`finger performance (Fitts 1954, Balkrishnan and MacK-
`enzie 1997). None of these studies can be easily applied
`to calculate the error resolution of the SlideBar due to
`the various methods employed. These studies do show
`the error to be based on angle, not position, and here the
`mouse controlled scrollbar may regain some lost
`advantage. Because the distance of movement for a
`mouse is much greater than that of the prototype
`SlideBar,
`the angles traversed during scrolling are
`greater. Rosenbaum et al. (1991) found that the optimal
`is about 458
`movement amplitude for
`the finger
`Rosenbaum et al. 1991). A study with positioning of
`sliders did show that errors in positioning are only a few
`percent for slider distances greater than about 5 to
`10 cm, which is comparable to the full range of the
`(Boff et al. 1986). But again,
`prototype SlideBar
`methods are not directly applicable, in this case largely
`because most participant movements were very large
`and involved primarily elbow and shoulder movements.
`One interesting result was that participants tended to
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`Analysis of a linear input device
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`5
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`overestimate short ranges and underestimate longer
`ones. These findings will have some bearing on future
`SlideBar implementations.
`While the prototype implementation of the SlideBar is
`a separate device that is placed next to the keyboard, we
`envision a production version that would be built into
`the keyboard. In addition to reducing the complexity
`and cost of the SlideBar, this would also improve its
`usability by providing stability to the device as well as
`putting it in a consistent and accessible position. We
`expect
`it would require only a small amount of
`additional area on a keyboard, making it especially
`desirable for
`laptop computers where space is a
`premium and a mouse is often not available.
`Some software design issues exist as well. We expect
`the SlideBar driver would automatically switch to
`control the vertical scrollbar of the focused window,
`however, other modes may be appropriate. The SlideBar
`will also likely be out of sync with a document when it
`moves into focus, as that document will not necessarily
`be scrolled to the depth corresponding to the SlideBar’s
`current position. Our intuition is to have the document
`snap to the SlideBar’s position as soon as that position
`starts to change, but there may be other ways to deal
`with this concern.
`
`3. Methods
`
`3.1. Conditions and materials
`
`We conducted an experiment to evaluate the prototype
`SlideBar device on a laptop computer (700 MHz Pentium
`III, 128 MB ram) with a screen resolution of 1024 6 768
`pixels. There were two independent variables: scrolling
`device; and document length. Three scrolling devices
`were tested: the prototype SlideBar, a standard mouse
`controlling a scrollbar, and a mousewheel. No accelera-
`tion algorithms were used with the mouse or mousewheel.
`The three documents lengths were three pages, 20 pages
`and 70 pages corresponding roughly to SlideBar resolu-
`tions of; less than one pixel, half a line and two lines,
`respectively. Dependent variables were the time to
`complete a scrolling task, the index of performance for
`a scrolling task and subjective satisfaction. The study was
`set up as a within-subjects design, so each subject
`performed both tasks with all three devices.
`Participants were first presented with a description of
`each device and how it worked. The study administrator
`demonstrated the devices and tasks on a practice
`document. Participants were instructed on how each
`exercise was to be completed, and then given unlimited
`time to practice device use and familiarize themselves
`with the tasks until they felt comfortable enough to
`
`proceed. On both the mousewheel and SlideBar, the two
`least familiar devices, subjects on average spent over a
`minute practicing, with several subjects spending several
`minutes. On the scrollbar, a device familiar to all of the
`subjects, average practice time was still nearly 45
`seconds, ensuring that the use of the device in context
`of the tasks was familiar.
`to gather
`Subjects were administered a pre-test
`demographic information and data about their previous
`experience with computers and various input devices.
`For the actual experiment, users completed all the tasks
`for a given device before proceeding to the next device.
`The order of the devices was randomized for each
`subject.
`After completing the tasks for the last device, users
`completed a post-test questionnaire that gathered their
`preferences and comments about the devices. They were
`also interviewed to gather any additional opinions about
`the experiment. The entire process took approximately
`1 h.
`
`3.2. Tasks
`
`Participants performed two types of tasks. For each
`task, a document of random words formatted in
`paragraphs was presented to the participant. Approxi-
`mately one-inch square, brightly coloured icons were
`placed randomly in the document as targets. Possible
`icons were circles,
`squares,
`rectangles, ovals and
`triangles. Colours and icons were chosen at random
`for each task. Prior to each task, a full screen page
`presented instructions for the upcoming task, including
`what graphical icon to look for. A button to begin the
`task was placed near the centre of the screen. The task
`document was presented when the participant clicked
`the button, ensuring the starting position of the mouse
`was near the centre of the screen. When the document
`was presented, it was scrolled all the way to the top and
`targets were never placed on the first page. The devices
`were presented in random order for each participant.
`During a trial for a specific device the other devices were
`physically present, but disabled.
`The first type of task was the common scrolling task
`of scanning a document for a target in an unknown
`location. A single icon target was placed randomly in
`the document. We refer to this as the target location
`task. We wished to study the effects of device resolution,
`especially for the SlideBar, so we used a second
`independent variable, document
`length, with three
`values,
`leading to nine total
`trials
`for
`this
`task.
`Participants were automatically timed from the moment
`the start button was clicked until they found and clicked
`on the target.
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`6
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`L. E. Chipman et al.
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`The second task type used a 20-page document of
`random words, which contained two graphical
`icons
`placed within it. The location of the first icon was
`randomly placed somewhere in the first half of the
`document. The second icon was always a fixed 10
`pages from the first. Participants were asked to find
`and select the first target then the second target, then
`the first again, repeatedly,
`for six clicks on each
`target. This
`is
`similar
`to Fitts’
`(1954)
`reciprocal
`tapping task. Participants were automatically timed
`from the beginning of the task (start button clicked)
`to the selection of the first target and from each target
`selection to the next.
`scrolling
`tasks, each type of
`In both types of
`described above was used. To locate the coloured
`icon, users progressed in ‘scan mode’, moving through
`the document quickly until they saw the icon for the
`first time. After roughly locating it in the document,
`users switched to ‘read mode’, moving slowly through
`the isolated section to bring the icon onto the screen
`and click it.
`
`3.3. Subjects
`
`There were a total of 24 participants in these
`experiments, 11 male and 13 female. All but three
`were right handed, and everyone used the mouse in
`their dominant hand and SlideBar
`in the non-
`dominant hand. They were drawn from a general
`university population, ranging in age from 18 – 30.
`Most did not have a computer science background,
`but used computers every day. All of the subjects were
`very familiar with the scrollbar, and all but two were
`mousewheel users.
`
`3.4. Hypothesis
`
`viously located targets should take advantage of this
`effect.
`
`3.5. Measures
`
`In the target location task, time for completion was
`measured. The index of performance (IP) (Card et al.
`1983) was then calculated:
`
`IP ¼ log2ðD=W þ 1Þ=MT
`
`where D is depth of target, W is width of target (fixed
`for all our trials) and MT is movement time. Because the
`target depths were varied at random for this task, it was
`not possible to use movement time directly as the
`performance measure. We chose index of performance
`because it normalizes the movement time based on
`target depth (Hinckley et al. 2002). Several cases were
`discarded when participants attempted to use the
`incorrect device for the trial.
`For reciprocal tapping tasks, 12 times were recorded.
`The first half of these was discarded to allow the
`participant to learn the location of the targets. Since the
`target distances and widths were fixed for every trial,
`movement time could be use directly as a measure of
`performance.
`After the completion of the study tasks, participants
`completed a post-questionnaire where they were asked
`to rate each device for speed of use, clarity of use and
`satisfaction of use. They were also asked to choose a
`preferred device and given the opportunity to comment
`in detail.
`
`4. Results
`
`4.1. Locating a target
`
`It was our hypothesis for the target location task
`that
`the SlideBar would outperform the standard
`mouse controlled scrollbar due to its advantages of
`two-handed input that eliminates the time necessary to
`acquire the scrollbar with the mouse. It was also
`expected that
`the SlideBar would outperform the
`mousewheel due to its nature as an absolute position-
`ing device vs. the relative nature of the mousewheel.
`This effect may be minimized for the shorter docu-
`ment length.
`It was our hypothesis for the reciprocal tapping
`task that
`the SlideBar would be faster
`than the
`other two devices. Only the SlideBar takes advantage
`of the haptic memory function of the human body
`and the task of repeatedly scrolling between pre-
`
`The mousewheel was significantly better than the
`other two devices for the target location task (figure
`2). The SlideBar had a higher mean performance for
`this task than the scrollbar, but the effect was not
`significant. For the target
`location task, univariate
`analysis of variance (ANOVA) showed device to be a
`factor, F(2,195) = 10.747, p 5 0.001. A
`significant
`post hoc Bonferroni
`comparison of
`the
`factors
`showed the mousewheel
`to perform significantly
`better than the scrollbar, p 5 0.001, with mean IP
`difference of 0.41. The mousewheel performed sig-
`nificantly better than the SlideBar, p = 0.047, with a
`mean IP difference of 0.22. The SlideBar was not
`significantly better than a scrollbar, p = 0.17, with a
`mean IP difference of 0.19.
`
`Petitioner Samsung Ex-1020, 0006
`
`

`

`Analysis of a linear input device
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`Figure 2. Target location task results. Error bars represent 95% confidence interval.
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`
`p 5 0.044; on average the SlideBar ranked 7.04, the
`mousewheel ranked 5.5, and the mouse with scrollbar
`ranked 6.16.
`
`5. Analysis
`
`The results support our hypothesis that the SlideBar is
`faster than a standard mouse controlled scrollbar for the
`reciprocal tapping task, but it does not support our
`hypothesis that the SlideBar is faster than a mouse-
`wheel. Though the data does not offer a clear reason for
`why the SlideBar was not faster than the mousewheel,
`our observations of the subjects offer one explanation.
`When using the SlideBar, users appeared to rely on the
`passive haptic feedback for document positioning.
`Although this was not available with the mousewheel,
`nearly every user started off by counting the number of
`‘spins’ of the mousewheel that separated the two icons.
`Users were then able to flick the mousewheel a fixed
`
`The analysis also showed document length to be a
`significant
`factor
`for
`the
`target
`location task,
`F(2,195) = 14.165, p 5 0.001. The interaction between
`device and document length was significant at p = 0.035.
`
`4.2. Reciprocal tapping
`
`For the reciprocal tapping task, the SlideBar had
`significantly better performance than the scrollbar
`(figure 3). For the reciprocal tapping task, univariate
`analysis of variance (ANOVA) also showed device to be
`a significant factor, F(2,499) = 7.79, p 5 0.001. A post
`hoc Bonferroni comparison of the factors again showed
`the SlideBar to be significantly faster than a scrollbar,
`p 5 0.001, with mean times of 5.8 s for the SlideBar vs.
`8.7 s for the scrollbar. Again, there was no significant
`difference in speed between the SlideBar and mouse-
`wheel.
`
`4.3. User preference
`
`In subjective preference, the SlideBar offered signifi-
`cant benefits over the scrollbar (figure 4). It also was
`preferred over the mouse wheel, but there was no
`statistically significant difference. Participants were
`asked to choose their preferred device and 14 of the 24
`chose the SlideBar. Users also gave subjective rankings
`on a scale of 1 (lowest) to 9 (highest) for speed, clarity of
`use, and satisfaction. For speed, the SlideBar signifi-
`cantly outranked the other two devices, F(2,69) = 15.5,
`p 5 0.001; on average the SlideBar ranked 8.08, the
`mousewheel ranked 5.46, and the mouse with scrollbar
`ranked 5.83. Users found no significant difference in
`clarity of use. Users were significantly more satisfied
`with the SlideBar than the mousewheel, F(2,69) = 3.28,
`
`Petitioner Samsung Ex-1020, 0007
`
`

`

`8
`
`L. E. Chipman et al.
`
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`Figure 4. Subjective satisfaction results. Error bars represent 95% confidence intervals.
`
`number of times to quickly switch between the targets,
`and this may have counterbalanced any benefit that the
`SlideBar offered.
`The results do not support our hypothesis that the
`SlideBar would outperform the other two devices at the
`target location task. The motivation for this hypothesis
`was that the two-handed nature of the SlideBar would
`give it an advantage over the other devices. Though
`previous research has established the advantages of two-
`handed input, under the parameters in this experiment,
`that effect did not make a significant difference. To the
`contrary, the results here showed that the mousewheel
`was
`significantly faster
`than both the SlideBar
`(p = 0.047) and scrollbar (p 5 0.001). For this task,
`the scrollbar clearly under performed. This is very likely
`due to the overhead of acquiring the scrollbar with the
`mouse at each target switch. Neither the mousewheel
`nor SlideBar suffers from this drawback.
`The interaction between device and document length
`was significant. For shorter documents the mousewheel
`shows a gain in performance over the other devices
`(figure 3). The poorer performance for the scrollbar can
`be attributed to the fact that there is constant time
`required to acquire the scrollbar with the mouse, and
`this time becomes a larger percentage of the overall
`movement time for short documents. The increase in
`performance for the mousewheel is likely because, for
`short documents, it is often possible to scroll to the
`target in a single motion of the mousewheel, eliminating
`time spent re-positioning the finger on the mousewheel.
`
`6. Conclusions
`
`We designed the SlideBar to take advantage of
`the
`potential
`benefits
`of
`two-handed
`use
`and
`
`constrained passive haptic feedback to give it an
`advantage over
`traditional
`scrolling devices