Brad A. Myers Challenges of HCI Design and Implementation A q, p About the Author BRAD MYERS is a Senior Research Computer Scientist at Carnegie Mellon University, where he is the principal investigator for the Garnet User Intdace Development Environment and the Demonstrational Intdaces Projtzt. entail.* [email protected] etting the user interface right is becoming criti- cal to the success of products, and everyone knows that designing and implementing human-computer interfaces is difficult and time-consuming. But why is this true? Should we expect that a new method is around the cor- ner that will make the design significantly easi- er? Will the next generation of user interface toolkits make the implementation trivial? No. This article discusses reasons why a focus on the user interface is important, and why user inter- face design and implementation are inherently difficult tasks and will remain so for the fore- seeable future. Why User interfaces Are Important A significant growth area for computers is their use in consumer electronics. This is why comput- er man&cturers like Apple are getting into the “personal digital assistant” market. The Friend21 project in Japan is a six-year project started in 1988 with the goal of promoting research and development into next-generation user interfaces, primarily intelligent agents and adaptive inter- faces. It is funded at about $120 million, and is a consortium of 14 major Japanese companies organized by the Ministry of International Trade and Industry. Friend21 stands for Future Personalized Information Environment Development [2GJ. The project believes that in the 2Ist century everyone will be using comput- ers for their everyday activities [26]. For the users of these devices, ease-of-use has become a prime factor in decisions about which ones to buy. interactions . . . january 1994 --- I,- _-_ C.._~ -_ ,’ _ ‘, : ,., .i. ,_- t ,- .*I There is substmtitil empirical evidence that Time is valuable, people do not want to read manuals, and they want to spend their time accomplishing their goals, not learning how to operate a computer-based system. Usability has also become critical for com- mercial desktop software. User’s demands on software have changed; they expect to be able to sit down and use software with little or no frus- tration. Readers of PC World magazine indicat- ed in a survey that usability was as important a review parameter as the more traditional issues of speed and features. Thus, usability is a do-or- die decision for developers, and is being cited with increasing frequency and explicitness in product advertisements. Although American industry has invested heavily in information technology, the expected productivity improvements have not been real- ized [2]. Usability at the individual, group and firm level has been cited as a culprit in this pro- ductivity paradox. For instance, the ever- changing computer environments caused by new product introductions and upgrades make continual learning demands on workers [2]. There is substantial empirical evidence that attention to usability dramatically decreases costs and increases productivity. A model of human performance, and a corroborating empirical study, predicted that a new worksta- tion for telephone operators would decrease pro- ductivity despite improved hardware and software. The resulting decision not to buy the new workstation is credited with saving NYNEX an estimated $2 million a year [12]. A different study reported savings from usability engineering of $41,700 in a small application used by 23,000 marketing person- nel, and $6,800,000 for a large business applica- tion used by 240,000 employees [17]. This was attributed to decreased task time, fewer errors, greatly reduced user disruption, reduced burden on support staff, elimination of training, and avoiding changes in software &er release. One analysis estimates the mean benefit for finding eachusabilityproblemat$19,300 [19].Amath- ematical model based on 11 studies suggests that using software which has undergone thorough usability engineering will save a small project $39,000, a medium project $613,000 and a large project $8,200,000 [24]. By estimating all the costs associated with usability engineering, another study found that the benefits can be up to 5000 times the cost [25]. Other studies have shown that it is impor- tant to have HCI specialists involved in design. A formal experiment reported that professional HCI designers created interfaces that had fewer errors and supported faster user execution than interfaces designed by programmers [3]. One reason is that training and experience in HCI design has a clear impact on the designer’s men- tal model of interfaces and of the user interface design task [l 11. This implies that HCI design is not simply a matter of luck or common sense, and that experience using a computer is not suf- ficient for designing a good user interface, but that specific training in HCI is required. In addition, poor user interfaces have con- tributed to disasters including loss of life. For example, the complicated user interface of the Aegis tracking system was a contributing cause to the erroneous shooting down of an Iranian passenger plane, and the US Stark ship’s inabil- ity to cope with Iraqi Exocet missiles was partly attributed to the human-computer interface [22]. Sometimes the im,dementcEtion of the user interface can be at fault. A number of people died from radiation overdoses partially as a result of faulty cursor handling code in the Therac-25 [33]. The importance of a focus on human-com- puter interaction has been recognized by indus- try, academia, government and the trade press. The Committee to Assess the Scope and interactions . . . january 1994Direction of