5.4 User interface consistency: an evaluation of original and revised interfaces for a videodisk library

Original and revised versions of the National Library of Medicine MicroAnatomy Visual Library system were evaluated with an empirical test of nineteen subjects. The versions of the program’s interface differed on issues relating to consistency of wording and screen layout, use of color coding, display of status information, and availability of help information. Each subject used both versions of the program to perform matched sets of tasks. The dependent variables were time to perform tasks correctly and subjective satisfaction as reported via the QUIS questionnaire. The revised version was statistically significantly faster for five of twenty tasks and more satisfying to use on a number of dimensions. The benefits of consistency and guidelines for design of interactive computer systems are discussed. Sparks of Innovation in Human-Computer Interaction, B. Shneiderman, Ed., Ablex Publ. , Norwood, NJ (1993) 220 Section 5: Public access Introduction Interactive computer systems are common in professional environments and are becoming more widely used in library and public information settings, such as online catalog systems, local area maps, and museum exhibit information. For these systems to be used effectively by untrained users the user interface must be carefully designed. Important considerations are: the multiple dimensions of consistency, cognitively-sound structuring, close correspondence of functionality to user goals, and small sets of choices provided to users at any one time (Lewis, et al. 90; Reisner 90; Nielsen 89; Kearsley 93). Initial informal references to consistency have turned into ambitious attempts at formal definitions that get more elusive as they are scrutinized (Reisner 90; Wiecha et al. 90). Kellogg (Kellogg 89) points out that “Consistency has no meaning on its own; it is inherently a relational concept. Therefore to merely say that an interface is consistent or that consistency is a goal of user interface design is also meaningless. ” The issue of defining consistency has even started a heated community debate (Grudin 92; Wiecha 92). It is now commonly accepted that when a competent user’s view of the system differs from the designer’s view of the system, then the system is inconsistent (Reisner 90; Grudin 89). The interface design community agrees that the user’s tasks and application domain are a major focus for providing consistency. At the same time, the community acknowledges that adhering too much to physical metaphors and the status quo can limit an interface’s usefulness by potentially ignoring inherent advantages of the computer medium. There is also a widely held belief that internal consistency (e.g., layout, terminology, color, etc.) is a crucial issue in the usability of highly interactive computer programs (Shneiderman 92; Reisner 90; Nielsen 89). Nielsen states that consistency leads to “improved user productivity by leading to higher throughput and fewer errors because the user can predict what the system will do in any given situation and can rely on a few rules to govern use of the system. ” Further, he points out “it is desired to have the system be consistent with users’ expectations whether formed by other applications or by non-computer systems. ” More encouragement for consistent design can be found in various guidelines documents (Brown 88; Smith & Mosier, 86). The goal of this project was to validate empirically that modest changes to an interface to make it more consistent with respect to the users’ domain and task context would increase comprehension, thereby decreasing completion times and increasing subjective satisfaction. History The NLM MicroAnatomy Visual Library system is an interactive computer system that allows users to view videodisk images of human cell structures. The images are accessed in a number of ways: via word search, videodisk frame number, and by prepared slideshows. It was created in 1987 by the National Library of Medicine to be used in medical schools and libraries by students and