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Lab 3.4 Exercises

3.4.1. Understand the Different Types of Models Used in HCI

a) How do we use mental models when designing a user interface?

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A1:

Answer: We use mental models to explain how people react in new situations by calling upon experiences from the real world. In user interface design, we work to bring familiar situations to most aspects of the design.

b) What metaphor does the spreadsheet employ? Why is it so effective?

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A2:

Answer: From Table 3.7 (see the answer to question e) we see that a spreadsheet employs the accountant's ledger sheet as its metaphor. This is a particularly simple metaphor with many direct links to the tasks being performed with a spreadsheet. This is a good example of the maxim “simple metaphors work best.”

c) Working in a familiar environment is necessary for most people. Discuss how the behavior of a word processor compares to the familiar typewriter in helping the user to work. What problems can arise?

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A3:

Answer: Perhaps the first obvious link is the keyboard, which appears very similar to that on a typewriter. Pressing a key in the word processor makes it appear on the screen. For conventional typing line after line, the mental model holds good, even for someone under pressure. Even pressing the backspace key keeps the mental model's accuracy. Pressing the return/enter key also has a familiar effect in that the cursor moves down a line and then back to the start of the line.

Perhaps the biggest problem is the complexity of the new environment. Although you are not likely to find someone who uses correction fluid to make corrections, how you edit the existing text is something that needs to be taught. Since the basic editing functions with cursor keys and mouse don't exist on the typewriter, new instructions on editing will have to be given to the user.

A similar problem occurs with people when working with Web-based applications. I see so many people who are used to moving with the cursor. They click on a link with the mouse, then click in the “Back” button, click on another link, and so on. In order to use the interface more efficiently they need to be taught about movement with the keyboard, for example.

d) Consider the metaphor of any common graphical operating environment. What metaphor is used? What familiar symbols are used to bring across this metaphor? Are there problems with this metaphor?

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A4:

Answer: The most common metaphor used for a graphical operating environment is the desktop. You have your documents, which you place in a filing cabinet. Documents that you wish to throw away are placed in a trash can. Once the users have recognized the familiar objects from the real world, they are in a position to make decisions on how to interact with the icons.

The problem arises as to how additional features can be added to the user interface where there is no equivalent in the real-life metaphor. For example, how is searching a document for the occurrence of a word or phrase to be added to the desktop metaphor? There is no easy answer since there is no such facility on the manual desktop.

In the latter case, a user interface designer has to resort to combining two or more metaphors in the same design. Often, the designer introduces new abstract metaphors for the very new features. These, of course, must be fully tested to determine whether the users form a suitable mental model and can then deduce how to use that component of the user interface. A good example here is the hyperlink in a web page. There is no equivalent in printed materials, so the blue underlined text was introduced as an abstract metaphor. When a user first uses a hyperlink, a little training is necessary. Once learned, the hyperlink metaphor can be carried into other applications like online help text and other hypertext systems.

e) There are other metaphors that have found their way into successful user interfaces. Create a list of applications and the possible metaphors that could be used, along with the knowledge this implies.

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A5:

Answer: Consider Table 3.7.

Lab 3.4 Self-Review Questions

In order to test your progress, you should be able to answer the following questions.


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