Academic journal article Human Factors

The Effects of Response Format and Other Variables on Comparisons of Digital and Dial Displays

Academic journal article Human Factors

The Effects of Response Format and Other Variables on Comparisons of Digital and Dial Displays

Article excerpt

INTRODUCTION

Many displays that in the past would have been in analog format are now being designed with digital readouts. Digital displays frequently can be more precise, more compact, and more economical than analog displays. In addition, digital displays often are assumed to be easier and/or more efficient to read (e.g., Goolkasian, 1984, 1988; Goolkasian & Bunting, 1985; Goolkasian & Park, 1980). That is not to say digital displays invariably are better, however. For example, Paivio (1978) showed that if the operator's task requires spatial processing, analog displays are processed faster than digital ones. In addition, analog representations may be superior to digital ones when derivative information is required (e.g., Kantowitz & Sorkin, 1983; Murrell, 1965) or where displayed values change rapidly (e.g., Helander, 1987).

From the display designer's standpoint, many past studies have been of somewhat limited value because they have been designed primarily to test theoretical rather than applied questions. Although the tasks in such studies sometimes have resembled those that real-world operators might have to do (telling time, matching one display with another, etc.), these tasks often have been selected more to test theoretical predictions than for their external validity. Furthermore, the variables that influence the relative effectiveness of analog and digital displays in these studies have been selected for similar reasons. Thus, they often have been less-than-optimal representations of the influencing factors that frequently must be considered in designing displays.

As indicated, under some conditions the superiority of digital displays disappears or, at least, is reduced to the point that other considerations might favor the use of an analog display. For the display designer it is not sufficient to know that digital displays are generally super/or to analog displays. Rather, the designer needs to know under what circumstances one is super/or to the other, and by how much. The present experiment was designed to test the influence of several practical variables on the relative effectiveness of digital and analog clock displays. These variables were selected because they frequently arise in the real-world use of displays and because it seemed likely that they would differentially affect digital and analog displays.

METHOD

Participants

The participants were 15 men and 10 women (mean age = 19.2 years) from introductory psychology classes at Washington State University. All had binocular near and far acuity (corrected if necessary) of 1.0 or better as assessed with a Bausch and Lomb Master Ortho-Rater. All gave informed consent and were reimbursed with credit for their psychology classes.

Apparatus and Materials

One of the independent variables was the two display types: a digital clock and an analog (dial) clock. Examples of the two display types are represented in Figure 1. All images were produced by a Commodore Amiga 3000 computer (Commodore Business Machines, Inc., West Chester, PA). Images were produced on an Optiquest (ViewSonic Corp., Walnut, CA) 14-inch (35.6 cm) multisync color monitor and were created in high-resolution (640 x 400 pixel) using Deluxe Paint IV graphics (Electronic Arts, Inc., San Mateo, CA). All numerals were in Helvetica 24-point font, 5 mm in height. The diameter of the dial was 6 cm. The rectangle enclosing the numerals of the digital displays was 2.3 x 1.4 cm. All images were produced in black, gray, and white; the approximate luminances of the three display colors were 0.4 cd/[m.sup.2] for black, 57 cd/[m.sup.2] for gray, and 140 cd/[m.sup.2] for white. The participant sat in a lounger chair with a padded headrest. The participant's head was kept against the headrest during all trials, maintaining a distance between the eyes and the monitor of approximately 36 inches (91.4 cm). Monitor height was set at the participant's eye level. …

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