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Article Excerpt
INTRODUCTION
Computer systems are ubiquitous in work environments and are becoming so in homes. Although approximately 51% of households in the United States reported having a computer system as of August 2000, older adults lagged in adopting them for personal use (Newburger, 2001). Newburger noted that fewer than 30% of households headed by someone 65 years or older reported owning a computer. In the second half of 2000 only about 15% of adults aged 65 years or older reported having Internet access, compared with about 56% for the U.S. population as a whole and 75% for those aged 18 to 29 years (Rainie & Packel, 2001). Computer system usability problems may be one reason older adults tend to lag behind their younger counterparts in computer ownership and Internet access (e.g., see Charness, 2005). Research indicates that novice older adults have difficulty using a mouse as a pointing device. Walker, Philbin, and Fisk (1997) showed that novice older adults were less accurate in using a mouse in a target acquisition task than were their younger counterparts. Adjustments they made to the interface (acceleration profiles) did minimize the differences between the two groups.
In a prior study, Walker, Millians, and Worden (1996) showed that older experienced mouse users have similar problems using a mouse and that their performance also improved with adjustments to acceleration functions. Smith, Sharit, and Czaja (1999) also showed that novice older adults experienced much greater difficulty than did novice younger adults in pointing tasks, particularly for double-clicking operations. Chaparro, Bohan, Fernandez, Choi, and Kattel (1999) showed that older adults exhibited slower performance with both a mouse and a trackball and exhibited higher ratings of perceived exertion with the mouse, as compared with younger adults. Charness, Kelley, Bosman, and Mottram (2001) found significantly more mouse errors during word-processing training for older than for younger novice adults, although this was not true for experienced word processors. Others have noted problems in the ability of older adults to control fine motor movements (e.g., Jagacinski, Liaou, & Fayyad, 1995: Liao, Jagacinski, & Greenberg, 1997).
A few mouse use properties may pose greater difficulty for older adults than for younger adults. First, the mouse is an indirect pointing device (see Greenstein, 1997) in the sense that the user must map the movement of the device in one plane (on the mouse pad or desk surface) with movement of a cursor on a different plane (the computer screen). Second, normal mouse settings provide some gain to the device such that both velocity and acceleration in the plane of the mouse surface is augmented in the plane of the screen. There is considerable evidence that older adults experience significant declines in spatial abilities (e.g., Salthouse, Mitchell, & Palmon, 1989) that might support this mapping and that older adults are generally slower on translation activities, such as those found in the digit-symbol substitution test (Salthouse, 1992). It is also the case that older adults show systematic slowing in many aspects of behavior (Salthouse, 1996).
Not all input devices require similar mapping operations. Touch screens and light pens offer a "where you point is where you go" (WYPIWYG) operation for cursor control. They also exhibit no gain. If it is the case that age differences in mouse use are partially accounted for by age differences in mapping operation efficiency, providing a direct positioning device should minimize these differences relative to an indirect positioning device such as a mouse. In this project we chose to compare the usability of both direct (light pen) and indirect (mouse) pointing devices for younger, middle-aged, and older adults.
The first goal for this experiment was to test hypotheses positing that difficulties in using a mouse may be attributable to age-related declines in spatial ability. To do this, we compared the effectiveness of the two types of input device for younger, middle-aged, and older adults who were experienced mouse users. We selected experienced individuals for several reasons. First, we found it nearly impossible to recruit younger novice adult computer users over a 1-year period, given the ubiquity of computers in the school systems. Second, we wanted a conservative test of the potential advantage of a light pen. Finally, given that future cohorts of older adults are more likely to be experienced users of computer systems, we wanted to be able to generalize our results to the case of experienced users, contrasting this study with prior studies that have examined mouse use by novices.
A second goal for this study was to contrast the use of preferred and nonpreferred hands for pointing tasks with direct and indirect positioning devices. Chronic conditions leading to impairments and disability show striking increases with age, particularly past the age of 65 (e.g., Benson & Marano, 1998). Hence, older adults in particular are more likely than younger ones to experience injury (e.g., musculoskeletal disorders) or disease (e.g., stroke, arthritis) resulting in loss of function of the preferred hand. We wanted to examine the case of adaptation to use of the nonpreferred hand, particularly for older adults. Prior research showed a complicated interaction of Hand x Device x Task for movement time in a small sample of young adults using a mouse, stylus, and trackball (Kabbash, MacKenzie, & Buxton, 1993), although hand was manipulated between subjects.
One factor that may mediate the ability to switch performance to the nonpreferred hand is degree of lateralization. Those who rely a great deal on one hand, to the exclusion of use of the other, may be expected to have greater difficulty in switching. Laterality questionnaire measures often ask for frequency of use of the two hands or preference for use. There is some indication in questionnaire studies that older adults are more strongly right lateralized for handedness than are younger adults. Gilbert and Wysocki (1992) showed a decrease with age in sinistrality and mixed-handedness with a two-item (writing, throwing) questionnaire that was returned by more than 1 million U.S. men and women. That is, there was greater concordance in hand use with increased age. Degree of handedness also tends...
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