INTL. JOURNAL OF HUMAN–COMPUTER INTERACTION, 25(5), 455–474, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1044-7318 print / 1532-7590 online
DOI: 10.1080/10447310902865040
1532-7590
1044-7318
HIHC
Intl.
Journal of Human–Computer Interaction
Interaction, Vol. 25, No. 5, April 2009: pp. 1–41
Review Study of Computer Input Devices
and Older Users
Computer
Taveira
and
Input
ChoiDevices and Older Users
Alvaro D. Taveira and Sang D. Choi
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University of Wisconsin–Whitewater
The fast aging of many societies and their increasing reliance on computers create a
compelling need to reconsider older users’ interactions with computers. Changes in
perceptual and motor skill capabilities that accompany the aging process bring
important implications for the design of human–computer interfaces. This study reviews
the recent research literature on computer input devices and their adequacy to the
elderly user. Significant findings from evaluative studies are summarized, and strengths
and weaknesses of the different input devices are outlined. Recommendations for
the design and selection of input devices are provided.
1. INTRODUCTION
Several countries have been experiencing significant aging of their populations as
result of a steady increase in longevity along with a concurrent drop in fertility
rates. In 2000 only five countries had more elderly (i.e., people aged 65 and older)
than youth (i.e., people younger than 15). Projections are that by 2030 all industrialized nations will share similar demographic structure, with some having more
than twice as much elderly than youth. Although elderly-to-youth ratios are typically much lower in developing countries, the future proportional increases in
their rates are expected to be greater than in developed countries (Gavrilov &
Heuveline, 2003).
Population aging poses considerable socioeconomic challenges for public
health, with an increased burden on welfare services, and for economic development, because of potential decline on workforce size and productivity. Thus, it
can be expected that national economic performance and quality of life will be
greatly influenced by the extent countries successfully adapt to these demographic changes. Furthermore, because human societies are increasingly dependent on technology, much of this adjustment ought to focus on the interaction
between older adults and the ever-growing variations of computers (Rogers &
Fisk, 2003).
Correspondence should be addressed to Alvaro D. Taveira, Department of Occupational &
Environmental Safety & Health, University of Wisconsin–Whitewater, 800 West Main Street,
Whitewater, WI 53190. E-mail: taveiraa@uww.edu
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Aging refers to the biological, psychological, and sociological changes occurring to human beings as they advance in chronological age. The aging process is
affected by multiple factors, including genetic makeup and environmental and
socioeconomic conditions. Different chronological thresholds have been suggested to define “old age” with additional subdivisions being applied as well (e.g.,
old-young, old-old). Otherwise, as pointed out by Rogers (1997), older adults are
not a homogeneous population, and chronological age should serve only as an
initial reference to the wide range of transformations experienced by individuals.
In fact, individuals as young as 40 years old may suffer age-related difficulties
interacting with computers.
Widespread and effective computer use by older adults carries important benefits to individuals and society. Computer access can be instrumental for the individual to stay employed, informed, intellectually active, and socially integrated.
The ability to operate a computer and other digital devices is becoming critical for
productive and independent (or interdependent) living in our society (Charness,
2001).
M. J. Smith and Taveira’s (2005) description of the misadventures of “Mr. Smith,”
a 50-year-old business person scrambling to use different computerized devices
while traveling, highlights some of the common difficulties faced by older computer
users. Even though the protagonist is a well-versed computer user, he faces difficulties associated to early aging effects on perception (i.e., presbyopia) exacerbated by a challenging physical environment found in a busy airport. Many other
older users, who are unfamiliar with computers, have their problems further
compounded by their inexperience.
There is growing use of computers among the elderly, but they still lag far
behind younger users and are often confronted with significant hurdles interacting
with computers (Czaja & Lee, 2003). Taking Internet access as a proxy for computer
use, in 2002 58% of American adults reported using the Internet, whereas only 4%
of adults age 64 and older did so (Lenhart et al., 2003). Barriers faced by older
users include lack of familiarity with computers, feelings of inadequacy, declining
visual and motor coordination skills, and other factors (Hendrix, 2000; Mann,
Belchior, Tomita, and Kemp, 2005).
The purpose of this review is to synthesize the available research on the operation of computer input devices from a perspective of their adequacy to the changing
capabilities of older users. In addition, this review aims at providing recommendations for the design and selection of computer input devices that incorporate
the needs of this critical population segment.
1.1. Older Users—How Different?
It is estimated that one in three American adults will experience a vision-reducing
eye disease by the age of 65 (Leonard, Jacko, & Pizzimenti, 2005). Research has
suggested that older adults may be less efficient in their visual processing than
younger ones requiring longer target acquisition times. Individuals with visual
impairments face difficulties recognizing fine details of icons and the small and
dynamic pointers used in Graphic User Interfaces (Fraser & Gutwin, 2000). These
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difficulties are primarily attributed to reduced visual acuity and constrained
visual field. Point-and-click tasks are known to pose problems to users with deficits
in vision or motor skills, and to older adults in general (Keates & Trewin, 2005).
Muscle strength and power begin declining by age 40 (Metter, Conwit, Tobin, &
Fozard, 1997), probably caused by changes in the number and size of muscle fibers
(Lexell, Downham, & Sjostrom, 1986). These changes in combination with a slowing
in the speed of conduction of nerve signals may be related to longer reaction times
(Fozard, Vercruyssen, Reynolds, Hancock, & Quilter, 1994) and to slower motions
and greater difficulty producing fine motor adjustments (Walker, Philbin, & Fisk,
1997).
Laursen, Jenson, and Ratkevicius (2001) studied the influence of age on performance and muscle activity during computer mouse tasks imposing high demands
on motor control. At self-determined speeds the elderly performed more slowly
than the young group. Furthermore, at predefined speeds, error rates were higher
for the elderly subjects, especially during double-clicking and high-precision
tasks.
Age-related changes that may interfere with the use of computer input devices
include reduced muscle strength (Mathiowetz et al., 1985), reduced range of
motion (ROM; Stubbs, Fernandez, & Glenn, 1993), and greater difficulty executing fine movements (Walker et al., 1997). Chaparro et al. (2000) compared four
age groups and reported substantial reductions in ROM for the wrist joint and in
hand grip strength for the older groups. When contrasting their findings with a
previous study (Stubbs et al., 1993) the authors determined that by age 90 individuals may experience ROM reductions of about 40% compared to 30-year-old individuals. Declines in ROM may interfere with the use of input devices, and
possibly increase the risk of musculoskeletal disorders (MSDs) for older computer
users (Chaparro et al., 2000; Chaparro, Bohan, Fernandez, Choi, & Kattel, 1999).
Finally, aging is associated with increased incidence of arthritis and of neurological
disorders such tremor, essential tremor, and Parkinson’s disease, all of which may
affect the use of input devices. It is estimated that by the year 2020 about 18.2% of
the American population will suffer from arthritis, most of them age 55 and older
(Reginster, 2002). Also, 96% of Parkinson’s disease cases occur in individuals
older than 50 (Van Den Eeden et al., 2003).
2. METHOD
Using a systematic approach to literature searching, we first defined an initial set
of keywords to guide the identification of relevant studies. Keywords utilized on
the electronic search included old, older, adult, age, aged, aging, elderly, computer input
devices, human-computer interaction, ergonomics, human factors, (alternative) keyboard,
non-keyboard input, trackball, mouse, joystick, touch pad, touch screen, trackpoint, musculoskeletal disorders, and voice input. Combinations of these keywords and terms
such as evaluation or assessment were also used in the search. Two librarians were
engaged in the process of identifying appropriate databases.
The search was conducted primarily using electronic databases, supplemented
by books and other printed materials retrieved from a network of libraries. Studies
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published in English were drawn from peer-reviewed journals, conference proceedings, edited books, and a variety of Web-based sources. Electronic resources
searched included ABI/Inform, Academic Search, ACM Digital Library, Applied
Science Full Text, Business Full Text, CINAHL, Emerald, Google Scholar, NetLibrary,
ProQuest, PsycINFO, PubMed, ScienceDirect, WilsonWeb, and Web of Science.
Most searches were conducted emphasizing the period from 1999 to 2007, with
older references added later in the process. More than 100 publications were initially
identified, and 85 of them selected for inclusion in this study. During a preliminary review, duplications and studies considered less relevant were discarded.
References concerning computer use by older adults or containing findings applicable to that age group were chosen. The selected references were carefully examined
by both authors.
In the following sections the most common used input devices, grouped under
the categories keyboards, pointing devices, and hands-free devices are reviewed from a
perspective of their suitability to elderly users. Comparisons and general recommendations for device design and selection are provided in the Discussion section.
2.1. Computer Input Devices
Input devices sense physical properties of the user (e.g., motions, touch, voice, etc.)
and convert them into predefined signals to the computer. Input devices must
comply with the users’ anatomic, biomechanical, perceptual, and cognitive needs
and capabilities. Epidemiological studies have associated long hours of computer
use with elevated rates of MSDs in the arms and neck (Bergqvist, Wolgast, Nilsson, &
Voss, 1995; Gerr, Marcus, & Monteilh, 2004). Furthermore, because the prevalence
of several MSDs increases with age (Woolf & Pfegler, 2003), additional caution in
the design of input devices for this population is justified.
2.2. Keyboards
QWERTY keyboard. The keyboard is the oldest and most common computer input device. The keyboard standard configuration (i.e., QWERTY) derives
from earlier typewriters and remains, with the addition of function keys and a
numerical keypad, mostly unchanged from its 1868 design (as in Lewis, Potosnak, &
Magyar, 1997). Some of the QWERTY keyboard shortcomings were identified as
early as the 1920s (as in Swanson, Galinsky, Cole, Pan, & Sauter, 1997) and relate
to the long finger-travel distances required, the heavy reliance on weaker and less
dexterous fingers, the preponderant use of the left hand, and the awkward postures entailed by its operation. The QWERTY keyboard use is associated with
wrist ulnar deviation, forearm pronation, wrist extension, and upper arm and
shoulder abduction (Rose, 1991; Simoneau, Marklin, & Monroe, 1999; Swanson
et al., 1997).
Although the evidence associating typing and MSDs of the upper limbs is
somewhat mixed (Gerr et al., 2004), the postural aspects of keyboarding have
received sustained research attention and have motivated the development of
multiple alternative designs (e.g., Kroemer, 1972; Malt, 1977; Nagaseko, Grandjean,
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Hunting, & Gierere, 1985). Keyboard design was shown to have an important
influence in upper limbs postures (Marklin, Simoneau, & Monrow, 1999; Rempel,
Barr, Brafman, & Young, 2007; Tittiranonda, Rempel, Armstrong, & Burastero,
1999), which are also affected by the nature of tasks performed and the workstation configuration (e.g., chair design and adjustment, work surface height).
Older adults are generally slower in selecting and tapping keys, particularly
novice users, but without marked reductions in accuracy (Bosman, 1993; Salthouse,
1984). Research suggests that skilled users engage in compensatory strategies that
frequently offset age-related deficits in typing performance (Bosman & Charness,
1996). Mann et al. (2005) surveyed a sample of older adults with disabilities and
found that when asked about possible improvements on the standard keyboard
“larger keys” was the most common request.
Split keyboards. The original split design was proposed by Klockenberg in
1926 (Çakir, 1995) as way to address (postural) issues in the standard keyboard
geometry. The comparative advantages of the split keyboard would include
reductions in ulnar deviation, wrist extension, and forearm pronation. The concept
was further developed and analyzed repeatedly in the past (e.g., Grandjean, 1978;
Kroemer, 1972; Malt, 1977; Nagaseko et al., 1985; Rempel et al., 2007; M. J. Smith
et al., 1998), and it is currently offered in a number of commercial products. Common
split geometries increase the distance between the right and left sides of the keyboard, rotate each half so that they are aligned with the forearms, and often have
a tented shape (i.e., gable angle) to reduce forearm pronation. Other variations on
the design include either fixed or independently adjustable halves.
Split keyboards have been shown to promote neutral wrist posture (Marklin
et al., 1999; Nakaseko et al. 1985; M. J. Smith et al., 1998; Tittiranonda et al., 1999)
and to reduce muscle, tendon, and nerve load (Gerard, Jones, Smith, Thomas, &
Wang, 1994; Rempel, Dahlin, & Lundborg, 1999; Somerich, 1994). In a recent laboratory study Rempel et al. (2007) evaluated six keyboard designs: (a) a conventional QWERTY, (b) a conventional QWERTY notebook, (c) a fixed split keyboard
with 6º split but no gable, (d) a fixed split keyboard with 12º split and 8º gable, (e) a
fixed split keyboard with 12º split and 14º gable and 0º slope, and (f) a fixed split
keyboard with 12º split and 14º gable and –7º slope. The authors concluded that,
although keyboard performance depends on the specific posture being measured,
when considering six wrist and forearm postures together (i.e., left and right ulnar
deviation, pronation, and wrist extension) the fixed split keyboard with 12º split
and 14º gable and 0º slope appears to provide the most neutral posture among the
keyboards tested.
Although available research does not provide yet conclusive evidence that split
keyboards reduce the risk of long-term discomfort or injury (M. J. Smith et al.,
1998; Swanson et al., 1997), there is evidence that users suffering from hand–wrist
pain may experience improvement in soreness and function with this keyboard
geometry (Tittiranonda et al., 1999). Thus, older users with hand and wrist pain
or discomfort could consider a split keyboard alternative, accompanied by workstation and work adjustments, as a medium-term solution. Several studies indicate that split designs are preferred by users (Çakir, 1995; Rempel et al., 2007,
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Tittiranonda et al., 1999), although an earlier meta-analysis indicated user preference for the standard keyboard (Lewis, 1995). Finally, typing speed is generally
slower (at least initially) on split keyboards, and adaptation to the new motor
skills required can be problematic (M. J. Smith et al., 1998), especially for older adults.
Other keyboard designs. Chord or chorded keyboards are characterized by a
small number of keys with different combinations defining inputs/characters.
These keyboards can convert chords into single characters and numbers, or syllables and phonemes (Lewis et al., 1997). The reduced number of keys minimizes
finger travel and reduces the overall size of the device, increasing portability.
Chord keyboards usually employ either two- or three-way switches and can be
specified either for one- or two-hand operation. Commercial software is also available
to convert standard keyboards into a chord mode. Although the reduced finger
travel required by chord keyboards could potentially benefit older users affected
by musculoskeletal impairments, the acquisition of new motor skills may be a
challenge. A wide variety of alternatives are being developed using the chord
design, but very limited evaluative research is available at this time regarding
comfort and productivity outcomes related to its usage.
Scooped keyboards are commonly configured in two or more concave surfaces
containing the keys, following either a QWERTY sequence or alternative layout.
The concave profile brings the keys closer together reducing finger travel and
possibly discomfort. Smith and Cronin (1993) demonstrated that wrist deviation
and muscle load were reduced on a scooped design as compared to the standard
configuration. Their study indicated a reduction in text entry output, without significant difference in errors. Participants preferred the scooped design in terms of
comfort and usability. Similarly, an electromyographic study conducted by Gerard
et al. (1994) showed a reduction of muscle activity during typing tasks in the
scooped keyboard. No published research on the interaction of elderly users with
this keyboard design could be identified at the time of this writing.
Other emerging technologies such as smooth and soft keyboards blur the distinction between keyboards and touch pads. Smooth keyboards consist of a thin
sensor array that recognizes the user’s fingers as they move over a flat surface
with the keys printed on it. Keyboard input is achieved by single finger contact,
with (optional) auditory feedback provided. Cursor positioning movements are
carried out using two fingers over the same surface. Combinations of finger
movements can be used to perform other operations on the same surface. These
keyboards may be rigid or flexible so they can be folded or rolled for transportation and storage, making them suitable for mobile applications. Because only one
key at a time can be touched in the keyboard mode, significant amount of time is
likely to be spent for finger travel between keys. This technology may offer an
environmentally robust interface with a smaller footprint than the traditional
keyboard and mouse arrangement (Westerman, Elias, & Hedge, 2001). However,
the need to acquire new motor skills (Shanis & Hedge, 2003), and the absence of
kinesthetic feedback could challenge older users. The use of additional auditory
signals to improve feedback may be ineffective as well considering age-related
hearing loss.
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2.3. Pointing Devices
Pointing devices allow the user to control cursor positioning and to select, activate, and drag items on display. Web interaction, for example, involves frequent
pointing and selecting tasks, commonly surpassing keyboard use. The pointing
device design and its operational characteristics, along with the workstation configuration, and the nature, duration, and pace of the tasks, affect body postures.
General concerns relating to the usage of pointing devices by the elderly include
prolonged static postures of the back and shoulders, frequent wrist motions and
excessive forearm pronation and wrist deviation.
Pointing devices are based on either absolute or relative cursor positioning. In
absolute mode the cursor position on the display corresponds to the position of
the pointing device over a surface, whereas in relative mode the cursor moves relative to its past position on the display. The nature of the task usually determines
the best mode of positioning (Greenstein, 1997). The overall performance of pointing devices is strongly influenced by its control-display (C-D) gain, that is, the
ratio between the displacement or motion applied on a control, and the amount of
movement displayed by the cursor on a screen.
2.4. Mice
The mouse has played a critical role as a primary input device (Po, Fisher, & Booth,
2004) and is the most commonly used nonkeyboard input device with desktop
computers (Atkinson, Woods, Haslam, & Buckle, 2004; Sandfeld & Jensen, 2005).
Keir, Bach, and Rempel (1999) pointed out that intensive mouse use has been
associated with increased risk of upper extremity MSDs, including carpal tunnel
syndrome.
Various aspects of mouse control such as moving, clicking, fine-positioning,
and dragging may be difficult for older people because of decline in motor control
and coordination. Increased propensity toward disabling conditions, such as
arthritis, compounds the problem. Riviere and Thakor (1996) found that older
adults were less successful in performing a tracking task with a mouse than
younger adults, with more difficult tasks producing greater differences between
age groups. Walker, Millans, and Worden (1996) compared older and younger
participants on a basic target acquisition task using different levels of mouse gain
acceleration. Older participants had more difficulty than younger participants,
especially with smaller and more distant targets. In a study by Walker et al.
(1997), older and younger participants performed a similar task, where acceleration was fixed but a speed-accuracy payoff matrix was added to determine how
strategy choices accounted for age differences in performance. Older adults
adopted a more conservative strategy and were less likely to modify that strategy
in response to different cost–benefit weights and made more submovements.
M. W. Smith, Sharit, and Czaja (1999) noted that older participants have more difficulty performing mouse tasks than younger ones, and differences in performance
attributable to age were found for the more complex tasks (i.e., clicking and
double-clicking).
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The extensive hand–eye coordination required by the mouse operation compounded by age-related decline in fine motor skills (Ranganathan, Siemionow,
Sahgal, & Yue, 2001) explain the poor performance in clicking tasks among older
users (Laursen et al., 2001; M. W. Smith et al., 1999). The mouse C-D gain may also
play a significant role in the degree of motor control required to perform a task.
Sandfeld and Jensen (2005) evaluated effects of motor and visual demands on
motor output in mouse clicking tasks. Their findings highlighted that the combination of small target sizes and high mouse gain reduced performance severely,
as measured by working speed and hit rate, and this was especially pronounced
in the elderly group. In addition, muscle activation levels were found to be generally
higher among older users.
Two potential problems with mouse use for older adults include fine-positioning
movements, such as controlling under and overshoot, and translating coordinates
in the desk space (movement of the hand in the plane of the desk surface) to those
in screen space (cursor movement across the screen).
2.5. Trackballs
Trackballs are the preferred pointing devices for numerous computer users, particularly for people with some form of motor impairment. For people with low strength,
poor coordination, wrist pain, or limited ranges of motion, rolling a trackball can
be easier than shuttling a mouse across the surface of a desk (Wobbrock & Myers,
2006). Trackballs may be preferred for reasons other than physical impairment.
Trackballs need little space in which to operate, unlike mice, which have large
desktop footprints. Trackballs can be embedded in consoles or keyboards, making them suitable for public terminals because they cannot be easily removed
(Wobbrock & Myers, 2006).
Age-related declines in sensory-motor and musculoskeletal systems may
interfere with the use of different computer pointing devices. Chaparro, Bohan,
Fernandez, Kattel, and Choi (1999) compared the performance of younger and
older adults in point-and-click and click-and-drag tasks using trackball and
mouse. The results of this study showed that older adults were slower than
younger adults performing both tasks with both input devices. Also, the two
age groups were slower with the trackball. Older adults in this study preferred
the trackball over the mouse. The older adults’ ratings of perceived exertion
were significantly higher than those reported by the younger participants, and
higher for the mouse than the trackball. The root mean square electromyographic values showed that both the elderly and younger participants produced
equivalent levels of muscle force during the movements. Although force production was similar, it represented a greater percentage of the elderly participants’ maximum voluntary contraction, as it is well known that muscle strength
declines with age. For instance, a study by Mathiowetz et al. (1985) found an
approximate 60% drop in grip strength by age 75 relative to age 25. Chaparro,
Bohan, Fernandez, Kattel, et al. (1999) concluded that the trackball might be a
better device for the elderly computer user, especially when performing tasks
requiring frequent and repetitive actions for prolonged periods.
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Chaparro, Bohan, Scarlett, Fernandez, and Choi (1999) compared older and
younger adults’ ability to select on-screen targets using a mouse and two trackball
designs (i.e., finger-ball and thumb-ball). The study findings included (a) for both
age groups the mouse presents the highest throughput, followed by the two
trackball designs; (b) for older computer users, the thumb-ball is associated with
greater levels of perceived exertion; and (c) when concurrently manipulating the
trackball and pressing a button performance deteriorates for both age groups. The
authors speculate that this latter effect is primarily a function of the click-and-drag
task and is because of the difficulty of maintaining the button pressed while manipulating the trackball with the thumb. This might explain why thumb-ball device
use was associated with greater levels of perceived exertion. Their findings suggested
that given the lower throughput capacity of the thumb-ball in conjunction with
the higher ratings of perceived exertion, the mouse may represent a better input
device. However, the finger-ball may offer some benefit to older persons with a
reduced wrist ROM.
2.6. Joysticks
A joystick consists of a lever mounted vertically in a fixed base. Displacement or
isotonic joysticks sense the angle of deflection of the joystick to determine cursor
movement. Isometric joysticks typically do not move or move minimally. They sense
the magnitude and direction of force applications to determine cursor movement.
Joysticks require minimal space, especially isometric ones, and can be effectively
integrated with keyboards in portable applications. The integration of joysticks
into keyboards allows users to switch between typing and pointing tasks very
quickly becauseof reductions in device acquisition time. For purely pointing tasks
the joystick performance is inferior to the mouse (Douglas & Mithal, 1994) and
requires significantly more practice for high performance. Joysticks are also very
sensitive to physiological tremor (Mithal & Douglas, 1996), and experience has
shown that these can be hard to master on portable computers. They suggest that
the inherently force-sensitive isometric joystick, operated by an unsupported finger,
provides very little inertial or frictional damping of the finger tremor transmitted
to it. Generally, joysticks tend to be best suited to continuous tracking tasks and to
pointing tasks that do not require a great deal of precision (Greenstein, 1997).
A trackpoint, a small isometric joystick placed between the letter keys G, H and B
on the computer’s keyboard, is one of the most common input devices among
modern notebook computers. It senses force from the fingertip, which results in a
cursor movement specified by a nonlinear transfer function. Research has shown
that the trackpoint seems to be quite challenging to master and rather difficult to
operate. Armbruster, Sutter, and Ziefle (2007) examined notebook input devices
(i.e., trackpoint and touch pad) comparing middle-aged to younger users in
point-click and point-drag-drop tasks. Middle-aged (40–65 years) users were significantly slower than younger (20–32 years) users when executing the different
tasks. Task performance was higher with touch pad than with trackpoint for both
age groups, and age-related performance decrements were less distinct when
using the touch pad (Armbruster et al., 2007).
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2.7. Touch Pads
A touch pad is a flat panel that senses the position of a finger or stylus and is commonly found as an integrated pointing device on portable computers such as laptops, notebooks, and personal digital assistants. Touch pads can be operated in
either absolute or relative mode. In applications where the touch pad emulates
the display, absolute mode is sometimes utilized, with potentially shorter target
acquisition times and increased accuracy. In portable applications touch pads are
usually very small, and because of size limitations they often operate in relative
mode. Touch pads typically recognize clicking through tapping and double-tapping
gestures. Arnaut and Greenstein (1986) recommend C-D gains for touch pads
between 0.8 and 1.0, for both absolute and relative modes. Touch pads offer good
display-control compatibility, can be positioned in different orientations (e.g.,
sloped or vertical), and can be easily accessed. Touch pads may feature visual or
auditory feedback to provide users with a more direct relationship between control
and display.
For older adults using portable computers, the small pad dimension poses
some challenges because of the size mismatch with the screen. Elderly users may
also experience difficulty with the complex motor skills involved in tapping the
touch pad (Wood, Willoughby, Rushing, Bechtel, & Gilbert, 2005). Along with
involuntary activation, accuracy could be an issue for finger item selection. As
the user taps the pad or simply lifts the finger from the tablet there is a tendency
for the cursor to move (Buxton, Hill, & Rowley, 1985). The issue can be addressed
by instructing users either to use a stylus instead of a finger or to keep their finger on the pad while activating the selection button with the other hand. A third
possibility is to correct this tendency through software (Greenstein, 1997). For
prolonged use touch pads are less comfortable than other input devices and may
lead to localized muscle fatigue under intense continual operation. Finally, other
input devices, such as touch screens, offer better eye–hand coordination than
touch pads.
2.8. Touch Screens
Touch screens allow direct user input on a display. Input signals are generated as
the user moves a finger or stylus over a transparent touch-sensitive surface placed
over the display. The input may be produced through a number of technologies
each with its own advantages and limitations.
Touch screens offer a direct input-display relationship, allow good hand–eye
coordination, and can be space efficient. They are appropriate for situations
where limited typing is required, for menu selection tasks, for tasks requiring
constant display attention, and particularly for tasks where training is neither
practical nor feasible such as public access information terminals. Parallax errors
due to separation between the touch surface and the targets can be an issue.
Visual feedback on current cursor location and on accuracy of operator’s action
helps reduce error rates (Weiman, Beaton, Knox, & Glasser, 1985). Depending on
their placement touch screens may be uncomfortable for extended use and the
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user’s hand may obstruct the view of the screen during activation. Touch screens
do not distinguish between actions intended to move the cursor over an item and
drag the item itself, which may be bothersome. Touch screens, even larger ones,
are error prone and are not suitable for extensive typing tasks (Plaisant & Sears,
1992). Wright et al. (2000) evaluated input devices for handheld computers and
compared three touch screen–based keyboards and a small physical keyboard.
They found reductions in accuracy and speed when entering text with the touch
screen, with users preferring by a wide margin the physical keyboard. Research to
this date suggests that further development is needed in touch screens, especially
small ones, to accommodate the visual and motor control capabilities of older
adults.
2.9. Light-Pens
The light-pen is a direct input device in that, unlike the mouse, there is no coordinate translation necessary for cursor positioning and target selection, which
could be beneficial to older users. Charness, Bosman, and Elliott (1995) compared
older adults’ use of a light-pen and a mouse, and they found performance to be
better with the light-pen. Movement time to a target takes twice as long with a
mouse as with a light-pen. Drag time goes up by 50% for novices using a mouse
compared to a light-pen. The pen appears to outperform the mouse, particularly
for novice older adults. Charness, Holley, Feddon, and Jastrzembski (2004) also
contrasted the performance of a mouse and a light-pen for three age groups
(young, middle-aged, old). They found that older (65–75 years) adults benefit
from direct input devices (e.g., light-pen) compared to indirect ones (e.g., mouse).
As discussed by the authors, the superior performance of older adults when
using the pen was referred to the fact that the direct input device allows an easy
mapping operation, with similar pattern found in the other age groups. Gobel,
Backhaus, and Kruger (as cited in Armbruster et al., 2007) also examined six
input devices comparing older to younger adults in a selection task. Their findings indicated that input devices with high movement analogy such as a light-pen,
which are based on direct and absolute positioning, performed better than input
devices primarily based on indirect and relative positioning, such as a touch pad
or a trackball.
Jastrzembski, Charness, Holley, and Feddon (2005), in a study involving
three age groups (i.e., 18–25, 45–55, and 65–75 years old) comparing mouse and
light-pen, detected performance differences depending on the nature of the
task. Their experiment simulated a typical Web browsing environment, in
which pointing and typing tasks are intertwined. All participants were familiar
with the mouse. Reductions in speed were observed between age groups for
both devices. However, contrary to prior research indicating superior light-pen
performance for pointing tasks, for mixed tasks involving pointing and
keyboarding older adults performed initially better with the mouse. Similar to
prior studies (e.g., Charness et al., 1995), the mouse was rated as easier to use
and more acceptable. Finally, the light-pen is not readily available to most computer users.
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2.10. Hands-Free Input Devices
Foot controls are unusual in human–computer interaction, and few commercial
alternatives are currently available. Although it is generally assumed that the foot
is slower and less accurate than the hand, this notion is not totally supported by
empirical data (Kroemer, 1971; Pearson & Weiser, 1988). Foot controls can provide effective pointing input and may minimize device acquisition time allowing
for quick switching between typing and pointing tasks. Dual foot controls may
allow cursor navigation and selection separately with good selection accuracy.
Foot controls can be used in conjunction with hand controls such as keyboard or
mouse to specify modes and secondary functions. Foot controls may be a valid
alternative to older users with limited hand and wrist mobility. They otherwise
required a seated position for operation, restrict user posture by making it difficult to shift position on the seat, and lead to static leg and back postures.
Head controlled devices have been considered a viable choice for virtual reality
applications (Brooks, 1988) and for movement impaired computer users (Radwin,
Vanderheiden, & Lin, 1990). Head switches can also be used in conjunction with
other devices to activate secondary functions. Unfortunately neck muscles offer a
low range of motion control, which typically results in significantly higher target
acquisition times when compared to a conventional mouse.
Eye-tracking devices employ a camera or an imaging system to visually track
some feature of the eye and determine the location of the user’s gaze. Eye-tracking
devices allow the user to look and point simultaneously, with item selection achieved
typically by eye blinking. These devices free the hands to perform other tasks,
nearly eliminate device acquisition time, and minimize target selection time. This
technology might benefit older users with limited manual dexterity. Significant
constraints to its wide application include cost, need to maintain steady head postures, frequency of calibrations, portability, and difficulty in operating. Other relevant
problems include unintended item selection and poor accuracy, which limits
applications involving small targets (Oyekoya & Stentiford, 2004; Zhai, Morimoto,
and Ihde, 1999).
Mouth-controlled input devices have been developed in the past, and a limited
number of commercial applications are available. Some of them use a joystick
operated by the tongue or chin with clicking been performed by sipping or blowing.
Typing tasks can be performed either by navigating and selecting keys through
an on-screen keyboard or through Morse code. The devices are helpful to users
with severe impairments but unlikely to be widely adopted because they are difficult
to operate.
Voice input may be helpful to older users in a number of situations, either as the
sole input mode or jointly with other control means. Speech-based input may be
appropriate, when the user’s hands or eyes are busy, when interacting with handheld computers with limited keyboards or (touch) screens, and for users with perceptual or motor impairments (Cohen & Oviatt, 1995). Jastrzembski et al. (2005)
investigated whether speech recognition may reduce age-related declines and
enhance performance. Three different age groups (i.e., 20–26, 44–55, and 65–78)
were asked to select a specific target using either a light-pen or speech recognition
software. The study results revealed that there were no age effects within device
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Computer Input Devices and Older Users
467
type, but response times were longer for speech recognition than the light-pen.
However, speech recognition was preferred over the light-pen input.
Speech recognition may enable older adults to interact effectively with a number of computerized appliances and eliminate, reduce, or supplement the use of
keyboards or other physical input devices. Voice input seems to be appropriate
when quick user input is required for descriptive information and when minimal
training is possible. The most promising aspect of voice-based input seems to be
as part of multimodal interactions. When used in conjunction with other input
modes voice recognition can reduce errors and allow for easier corrections, and
increase flexibility of handheld devices to different environments, tasks, and user
needs and preferences (Cohen & Oviatt, 1995). Although voice input may be an
alternative for users affected by MSDs, its extensive use may lead to vocal fatigue
(Welham & Maclagan, 2003).
Brain input devices are still in their infancy, but they may provide in the future a
nonmuscular channel for interacting with computers and the environment. Increasing understanding of brain physiology and expanded capabilities and affordability
of computers have created new opportunities for (older) adults with an array of
neuromuscular disorders. These new input devices may provide severely impaired
users with improved communication capacity, and eventually with motor control
abilities through neuroprostheses. Current brain input devices are limited by
their low information transfer rates, which makes them useful for augmenting
communication but perhaps insufficient for neuroprosthesis control (Wolpaw,
Birbaumer, McFarland, Pfurtscheller, & Vaughan, 2002). Progress in brain computer interaction will depend on the coordinated development of multiple basic
and applied disciplines. Ergonomics could contribute to the appropriate matching
of applications and users, to increased user acceptance, device usability, cosmesis,
and the determination of which augmented capabilities are most valued by users
(Wolpaw et al., 2002).
3. DISCUSSION
The ubiquity of computers and the growing presence of elderly users, with a
changing pattern of capacities and preferences, impose important considerations
for the design and selection of input devices. In this study we set out to review
and consolidate some of the available research on the operation of computer
input devices from a perspective of their adequacy to older users. Table 1 summarizes the input devices reviewed in this study and describes their main functional
characteristics as related to older users.
Keyboards in their conventional (i.e., QWERTY) configuration remain the most
common input device for data and text entry. Although the shortcomings of the
QWERTY design are well documented, to this date the multiple attempts to
replace this configuration with alternative ones have found limited success. Among
alternative geometries the split keyboard has received the greatest amount of
attention from research and product developers alike. Available research indicates
that the split geometry encourages neutral wrist postures and reduces pressure
and loads on muscles, tendons, and nerves. However, the evidence of its long-term
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Table 1:
Device
Keyboard
Summary of Computer Input Devices and Their Main Characteristics
Type
QWERTY
Split
Chord
Scooped
Smooth/soft
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Nonkeyboard
Mouse
Trackball
Joystick
Trackpoint
Touch pad
Touch screen
Light-pen
Hands-free
Foot controls
Head controls
Eye-tracking
Mouth controls
Voice input
Brain input
Best Application
Data and text entry
Improved arm-hand
postures
Minimal finger
travel, portability
Shorter finger travel,
better posture
Small footprint,
portability
Pointing & selection
tasks
Pointing & selection
tasks
Tracking & pointing
tasks
Pointing, small
footprint
Display-control
compatibility
Intuitive, menu
selection
Intuitive, pointing &
selection
Reduced hand
mobility
Upper limbs
impairment
Motor control
impairment
Severe mobility
impairment
Motor impairment
Severe motor
impairment
Limitations
Comments
Poor postures
Learning required
Conventional
Preferred alternative
Learning required
Limited evidence
Learning required
Limited evidence
No kinesthetic
feedback
Demanding control
Limited evidence
Slower than mouse
Sensitive to tremor
First alternative
choice
Not recommended
Hard to control
Not recommended
Selection accuracy
Poor finger item
selection
Direct user input on
display
Direct positioning
device
Limited research
evidence
Only for special
needs users
Still in development
Typing accuracy
Availability
Restrain seated
postures
Motion range &
control
Portability, accuracy
Motion range &
control
Accuracy, voice
fatigue
Still in development
Standard choice
Only for special
needs users
Complement other
devices
Basic research
needed.
effects on discomfort and MSDs incidence is not yet conclusive (Amell & Kumar,
1999). A recent study by Rempel et al. (2007) concluded that when considering
overall upper limbs postures, a fixed split keyboard appears to provide the most
neutral posture among six keyboards tested. For (older) users experiencing musculoskeletal discomfort the use of a split keyboard, in conjunction with workstation adjustments (M. J. Smith, Carayon, & Cohen, 2003), could be a valid strategy.
Initial reductions in typing speed and accuracy, as well as short-term issues in the
development of new motor skills, can be expected.
Common concerns relating to the use of pointing devices by older adults include
prolonged static and constrained postures of the back and shoulders, frequent
and awkward wrist motions, and taxing visual and motor skill demands. The mouse,
the most commonly used nonkeyboard input device, consistently presents higher
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Computer Input Devices and Older Users
469
speed, accuracy, and overall productivity under most circumstances. Alternatives
to the mouse are usually considered for portable applications, and for accommodating age-related functional changes. These capacity declines may include reduced
muscle strength, reduced ROM, and greater difficulty executing fine hand–eye
coordinated motions.
Among the alternatives research suggests that the trackball can be a suitable
device for older users, especially for those with low strength, reduced motor coordination, wrist pain, or limited ranges of motion. They can be good choices for
tasks requiring frequent and repetitive actions for prolonged periods. Although
not matching the mouse performance, trackballs were preferred by older adults
(Chaparro, Bohan, Fernandez, Kattel, et al., 1999). Larger trackballs (i.e., finger
and palm operated) presented higher performance than smaller thumb-operated
ones (Chaparro, Bohan, Scarlett, et al., 1999; Wood et al., 2005). Trackballs are
good choices for portable applications and public access computers as well.
Touch pads are an integrated feature in most notebook computers offering good
display-control compatibility and a small footprint. Main concerns for older users
include (typical) small pad dimensions, complex motor skill demands, and involuntary activation. Touch pads are less comfortable than other input devices, and
their prolonged use may lead to localized muscle fatigue.
Touch screens offer a direct input-display relationship, promote good hand–eye
coordination, and are very space efficient. They are favored in applications that
require constant visual monitoring and are appropriate for menu selection tasks
and limited text entry. Touch screens fit well situations where quick unpracticed
interaction is needed, such as in public access terminals. They are not suitable for
extensive data entry, because of accuracy and discomfort issues, and further
development is still needed to accommodate the visual and motor control capabilities of older users.
Light-pens present high movement analogy based on direct and absolute positioning, which could be beneficial to older users. For simple pointing tasks, it has
been suggested that the performance of light-pens could even be superior to that
of the mouse, although the light-pen is rated as less acceptable than the former
(Charness et al., 2004). For mixed tasks (i.e., pointing and typing) it was found
that older users were initially less efficient with the light-pen than with the mouse,
with no differences in subsequent trials (Jastrzembski et al., 2005). When compared to voice input light-pens produced shorter response times for target selection but received lower acceptance ratings. The light-pen remains an uncommon
pointing device, with very few commercial options available, and it does not
appear to be a clear choice for the elderly.
Although the joystick requires minimal space and can be easily integrated with
keyboards in portable applications, its performance is inferior to that of the
mouse and the touch pad, requiring more practice for skilled operation, and it is
very sensitive to physiological tremor. Joysticks in general, and the trackpoint in
particular, are not recommended options for older users.
A number of emerging technologies are making hands-free computer input
possible. Some of these technologies, such as foot and head controls, can be helpful to older individuals with specific motor control limitations. Other devices, such
as voice recognition systems, may be used either as a stand-alone input mode or
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in conjunction with conventional devices to support or augment the older user
capabilities and mitigate age-related declines. Current voice recognition technology
does not match the performance of common positioning input devices. On the
other hand voice recognition is well accepted by older users and does not seem to
pose any particular barrier to that age group. Technologies such as eye and brain
input hold great promise for the future but have limited current applications and
still face a number of development uncertainties before widespread adoption.
The integration of additional feedback, such as haptic, visual, and auditory signals,
can assist older users’ interactions with computers, and compensate for age-related
impairments. In particular, the addition of auditory feedback seems to produce
consistent improvement for a number of computer tasks, regardless of user experience (Jacko et al., 2004; Jacko et al., 2005).
Future research and development on computer input devices that further accommodate age-related perceptual and motor control declines is warranted as larger
numbers of older adults become computer users. With the ever-growing variety of
input devices, HCI research is lagging behind the pace of new product development.
Limited information is currently available on the adequacy of input devices to the
needs and capabilities of older users. In particular, there is little knowledge about
the long-term effects of these technologies on MSD incidence and prevention.
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