Firm foundation in the main hci principles, the book provides a working
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Human Computer Interaction Fundamentals
Figure 3.2 An example of a hierarchical task model of changing a font for a short text. Note that
a specific interface may be chosen to accomplish the subtasks in the bottom. 3 3 H U M A N FA C T O R S A S H C I T H E O R I E S consider two aspects of human performance: one that is cognitive and the other ergonomic. In the remainder of this section and in Section 3.2, we focus on the cognitive aspects. Ergonomic aspects are dis- cussed in Section 3.3. Norman and Draper [1] spoke of the “gulf of execution/evaluation,” which explains how users can be left bewildered (and not perform very well) when an interactive system does not offer certain actions or does not result in a state as expected by the user (Figure 3.3). Such a phenomenon would be a result of an interface based on an ill-modeled interaction. A user, when solving a problem or using an interactive system to do so, will first form a mental model that is mostly equiva- lent to the hierarchical “action” plan for the task (see Section 3.1.1). The mismatch between the user’s mental model and the task model employed by the interactive system creates the “gulf.” On the other hand, when the task model and interface structure of the interactive system maps well to the expected mental model of the user, the task performance will be very fluid. Memory capacity also influences the interactive performance greatly. As shown in Figure 3.1, there are largely two types of memory in the human cognitive system: the short term and the long term. The short-term memory is also sometimes known as the working memory, in the sense that it contains (changing) memory elements meaning- ful for the task at hand (or chunks). Humans are known to remember about eight chunks of memory lasting only a very short amount of time [2]. This means that an interface cannot rely on the human’s Download 4.23 Mb. Do'stlaringiz bilan baham: |
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