Academic journal article Human Factors

Touch a Screen or Turn a Knob: Choosing the Best Device for the Job

Academic journal article Human Factors

Touch a Screen or Turn a Knob: Choosing the Best Device for the Job

Article excerpt

INTRODUCTION

A successful human-system interaction depends on the human's ability to communicate with the system--to direct it to perform an action, to request a piece of information, and so on. Such communication occurs through use of an input device such as a keyboard, button, knob, mouse, touch screen, or voice activation. The present research focused on variables that could influence input device use. For example, does the optimality of an input device depend on the task being performed? Is performance with a given input device influenced by the age of the user?

Recognition that one input device might be better relative to another device for a particular task is certainly not new. In fact, new input devices often are developed in an attempt to compensate for the limitations of existing devices. However, a systematic analysis of the interactions among task demands, user capabilities, and input device characteristics is lacking.

Input devices may be categorized as direct devices and indirect devices. A direct input device is one for which no translation is required between the activity performed by the person and the action of the device; examples include a touch screen, a light pen, or voice activation. Indirect devices, however, require a translation between the activity of the person and the action of the device. For example, a mouse moves in one dimension on the desktop and the cursor on the screen moves in a different dimension; moreover, depending on the settings of the mouse, a 1-inch movement of the mouse might result in a 3-inch movement of the cursor. Other examples of indirect devices include trackballs, joysticks, and rotary encoders.

The input device categories of direct and indirect have advantages and disadvantages, as summarized in Table 1. Generally, direct devices are best for discrete, pointing, and ballistic types of tasks. Indirect devices yield better performance for precision tasks or repetitive tasks. However, these generalizations are based on studies in which devices were compared for tasks in isolation (for reviews, see Greenstein, 1997; Greenstein & Arnaut, 1987). Whether these studies predict input device superiority and apply to the variety of tasks that must be performed in a complex system are empirical questions.

An additional research question is whether the pattern of advantages and disadvantages for input device categories will generalize across user groups differing in age. As people age, motor behaviors change such that older adults, compared with younger adults, take longer to make similar movements, and their ability to maintain continuous movement declines, coordination is disrupted, and movements are more variable (for a review, see Vercruyssen, 1997). In addition, older adults have more "noise" in their movement control system (Walker, Philbin, & Fisk, 1997), less effective perceptual feedback (Walker et al.), reduced working memory capacity (Zacks, Hasher, & Li, 2000), and declines in spatial ability (Salthouse, 1992). All of these characteristics associated with older age could conceivably influence use of input devices.

Some studies have directly examined older adults' use of input devices. When using a mouse, older adults tend to make more errors and are slower than younger adults (Charness, Kelley, Bosman, & Mottram, 2001; Smith, Sharit, & Czaja, 1999; Walker et al., 1997), even if they are experienced mouse users (Walker, Millians, & Worden, 1996). However, few researchers have compared older adults' performance across different input devices. One notable exception is a recent study by Charness, Holley, Feddon, and Jastrzembski (2004) in which performance using a mouse and a light pen was compared across young, middle-aged, and older adult age groups. They found that using a light pen reduced age-related differences for a menu target acquisition task. They suggested that direct devices might be generally better for older adults because they reduce the need for a translation from the activity of the user to the action of the device. …

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