In two experiments, each using a different product (either a CD-ROM based eleclxonic book or an interactive voice response system), we compared the usability problems uncovered using low-and high-fidelity prototypes.One group of subjects performed a series of tasks using a paperbased low-fidelity prototype, while another performed the same tasks using either a high-fidelity prototype or the actual product.In both experiments, substantially the same sets of usability problems were found in the low-and highfidelity conditions.Moreover, there was a significant correlation between the proportion of subjects detecting particular problems in the low-and high-fidelity groups.In other words, individual problems were detected by a similar proportion of subjects in both the low-and high-fidelity conditions.We conclude that the use of low-fidelity prototypes can be effective throughout the product development cycle, not just during the initial stages of design.

Menus, lists, and forms are the workhorse dialogue structures in telephone-based interactive voice response applications. Despite diversity in applications, there is a surprising homogeneity in the menu, list, and form styles commonly employed. There are, however, many alternatives, and no single style fits every prospective application and user population. A design space for each dialogue structure organizes the alternatives and provides a framework for analyzing their benefits and drawbacks. In addition to phone-based interactions, the design spaces apply to any limited-bandwidth, temporally constrained display devices, including small-screen devices such as personal digital assistants (PDAs) and screen phones.

The current generation of telephone interfaces is frustrating to use, in part because callers have to wait through the recitation of long prompts in order to find the options that interest them. In a visual medium, users would shift their gaze in order to skip uninteresting prompts and scan through large pieces of text. We present skip and scan, a new telephone interface style in which callers issue explicit commands to accomplish these same skipping and scanning activities. In a laboratory experiment, subjects made selections using skip and scan menus more quickly than using traditional, numbered menus, and preferred the skip and scan menus in subjective ratings. In a field test of a skip and scan interface, the general public successfully added and retrieved information without using any written instructions.