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2.6 Human–Computer Interaction
In 2001, 72.3 million workers used a computer at work in the United States (BLS, 2002). These workers accounted for 53.5% of total employment in 2001. Computer systems, including both hardware and soft- ware, have become more and more sophisticated. End users have different levels of skills and knowledge.
But regardless of their skill and knowledge levels, end users have a single goal in common: to complete the given tasks as soon as possible or find what they want in time when surfing the Internet. For exam- ple, consider a voice recognition system. Many companies are now providing voice response systems rather than a touch-tone response system. Some customers will find it convenient, but others will find it difficult. The voice recognition technology may well be advanced enough not to worry about the
0 5 10 15 20 25
Frequency
Psychosocial Personal Physical
Psychosocial 1 2 2 2 1 1
Personal 1 1 6 2 2 1
Physical 2 1 5 3 7 4 4 4 3 2 1 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7
Standard deviation (b)
(a)
0 5 10 15 20 25
Frequency
Psychosocial Personal Physical
Psychosocial 6 1 2
Personal 4 5 5 1 1
Physical 13 8 6 3 1 2 1 1 1
1 1.5 2 2.5 3 3.5 4.5 5 5.5 6 6.5 7
Odds ratio 4
FIGURE 2.2 Histograms and frequencies of odds ratio (OR) and standard deviation (SD). (a) OR distribution:
about 40% (23/58) of OR values are less than 1.5 and overall trend of the distribution is exponentially decreasing.
(b) SD distribution: about 98% (57/58) of SD values are less than 0.5.
question, “How can my speech be perfectly recognized through the phone?” But for those who have a strong accent or who are beginning to learn English, the voice recognition system may not be favorable.
Human–computer interaction (HCI) is a relatively young field, still developing compared with other research fields. A wide range of groups are interested in HCI, including researchers in linguistics, social and behavioral sciences, computer engineering, information technology, and so on.
There are three major topics in HCI:
(1) Understanding user characteristics (2) Providing design principles and guidelines (3) Conducting usability tests
These topics require the collaborative work of experts from a variety of disciplines. Figure 2.3 illustrates a conceptual map for the relationships. HCI professionals, including HF specialists, collect user data and give user-characteristics information to the system developers so that the developers know more about what the user wants and how the user behaves. The HCI professionals also provide the user more user-friendly sup- port materials with help from system developers. The related disciplines shown in Figure 2.3 are examples.
2.6.1 Understanding User Characteristics
“User-friendly” is a very familiar term in HCI. It indicates that consumers now prefer software packages or devices having features that are easy to use or manipulate. However, considering the nature of software, which ranges from performing very simple functions such as basic calculations to extremely complex
System developers
Hardware engineers
Software designers/
programmers
End-users Levels
• novice
• experienced
• expert
Tasks
• simple
• medium
• sophisticated HCI
professionals
• Understanding user characteristics
• Providing design principles and guidelines
• Conducting usability tests
Collect user data
Social/
behavioral sciences
Support material/
training Provide
user information
Support technology
Human factors Computer
science Information
technology Linguistics
Cognitive science/
engineering
FIGURE 2.3 Conceptual diagram of relationships among system developers, HCI professionals, and end users. Not all of the related fields in HCI are present.
functions such as control of a nuclear power plant, it is not easy to define “user-friendliness.” Also, as products become more complex, the necessary interfaces will likely have numerous displays, menus, dis- play formats, control systems, and many levels of interface functions. The trend toward a greater number of functions is an important problem because the additional functions make the interface more complex and increase the number of choices the user must make (Wickens et al., 2004), thereby decreasing user- friendliness. Any product that is designed without paying attention to the user often leaves a huge gap between the user’s capabilities and the expectations the product places on the user. The goal of the HF specialist is to help narrow this gap by understanding and paying attention to the needs of the user rather than what the system developers want to make.
Table 2.7 shows some examples of the user characteristics that system developers must consider. For example, many elderly people are not satisfied with the font sizes on cell-phone displays; providing flex- ibility on font size makes older people more comfortable. In another example, most end users do not understand the error messages provided by personal computers.
2.6.2 Providing Design Principles and Guidelines
Design principles require consistency and good usability. Consistency means providing new systems that are easy to learn: for example, most MS Windows applications have menus on the top of the screen and a File menu on the top left containing Open, Save, and Print commands in common. Anyone who is famil- iar with any Windows software can use another Windows software without any problem. However, con- sider the menu structures built into cell phones. No cell phones have the same or even similar menu structures to indicate “start over.” This lack of consistency can be a serious problem for consumers as they switch between systems. Usability means ease of learning, ease of use, and ease of recovering from errors.
The concept of usability will be considered in the next section.
In general, design principles and guidelines are generated by theoretical models such as the GOMS (Goals, Operators, Methods, and Selection rules) model developed by Card et al. (1983). Many systems developers have the strong belief that people will become skilled in their systems’ use and will want to have efficient methods for accomplishing routine tasks. This GOMS model can predict the impact of design decisions on this important measure of success. For example, consider the goal of send- ing an e-mail to a friend. The user will open a blank message screen, select a recipient or type an e-mail address, write a message, and click on the send button. The GOMS model assumes that the user sets a goal (sending an e-mail) and subgoals, if necessary, that the user achieves by way of methods and selection rules. A method is a sequence of steps that the user should follow, while selection rules are the choice of one or another method, such as “select a recipient” or “type an e-mail address,”
for example.
TABLE 2.7 Examples of User Characteristics and HCI Considerations
User Characteristics Considerations for System Developers
Age ● Flexibility on font size for older people
● Selection of words for children
● Sensitivity of mouse and keyboard Knowledge of computer ● Understandable error messages
● Instruction manual
● Help menus
Disability factor ● Use of color for the color-blind
● Voice recognition and response system
● Keyboard size
Preference ● Dominant hand when using a mouse
● Flexibility of color selection
● Option of auditory feedback
2.6.3 Conducting Usability Tests
Even a carefully designed system that uses the best theories must be evaluated in usability tests. Usability tests involve typical users using the system in realistic situations. All details of difficulties and frustrations the testers encounter should be recorded for the purpose of upgrading software quality. Most usability specialists use a variety of prototypes, from low- to high-fidelity methods. Low-fidelity methods, gener- ally used early in the design process, include index cards, paper stickers, paper-and-pen drawings, and storyboards. Storyboards are a graphical depiction of the outward appearance of the software system, without any actual system functioning. High-fidelity methods include fully interactive screens with the look and feel of the final software (Wickens et al., 2004).
When designers are conducting usability testing, whether early in the low-fidelity prototyping stages or late in the design lifecycle, they must identify what they are going to measure, often called usability metrics. Usability metrics tend to change in nature and scope as the project moves forward. In early con- ceptual design phases, usability can be evaluated with a few users and focuses on the qualitative assess- ment of general usability (whether the task can even be accomplished using the system) and user satisfaction. Low-fidelity prototypes are given to users, who then imagine performing a very limited sub- set of tasks with the materials or screens (Carroll, 1995). At this point, there is usually little to no quanti- tative data collection; simply talking with a small number of users can yield a large amount of valuable information. As the design takes on more specific form, usability testing becomes more formalized and often quantitative. Several versions of usability questionnaires are available, and some companies have developed their own usability testing metrics. In general, effectiveness, efficiency, and subjective satisfac- tion are the main usability measures.
Usability testing is not limited to product designs or software development. As computers become more popular, companies develop their websites, trying to attract more visitors by providing more serv- ices. In many cases, it is really difficult for a user to find what he or she wants from websites, especially when the website contains tremendous amounts of data. For example, Yu et al. (1998) reported that the Kodak website (www.Kodak.com) contained over 25,000 pages and 74,000 files in 1998. In terms of traf- fic size, Kodak.com averaged around one million hits daily, including roughly a quarter of a million pages viewed and accessed by some 24,000 unique visitors each day. However, the main top-level design remained unchanged, and the visitors had a hard time finding what they wanted as a result of broken links and unmatched menu structures. The effort to develop a new design was started from the guestbook of Kodak.com, which provided important information on what the visitors wanted most (user’s needs) and which problems the visitors had (user’s behavior). As seen in this Kodak.com case, users are the core factor of design. No products will be favored without considering the user. In response to the growing demands for usability, the U.S. Department of Health and Human Services developed a website about usability (http://www.usability.gov/). This website provides useful information such as federal guidelines, Internet statistics, and lists of usability-related events.