|Human Performance at the Computer – Part 2: Making Applications More Responsive|
|Human Performance at the Computer – Part 3: Perceived Performance|
|Human Performance at the Computer – Part 4: On the Way to Performance-Oriented UI Guidelines|
|The Three Pillars of Human Performance at the Computer – Which One Fits Best?|
|Performance – Merely a Technical Problem?|
|Waiting at the Computer: Busy Indicators and System Feedback – Part 1|
|Waiting at the Computer: Busy Indicators and System Feedback – Part 2|
|Waiting at the Computer: Busy Indicators and System Feedback – Part 3|
|Research-Based Web Design & Usability Guidelines|
|GUI Bloopers checklist (PDF version)|
By Gerd Waloszek, SAP User Experience, SAP AG – October 4, 2008
In previous articles, I have discussed human performance at the computer and distinguished between three aspects of performance: system performance, system responsiveness, and human performance (see, for example, The Three Pillars of Human Performance at the Computer – Which One Fits Best?). I pointed out that in order to improve the overall performance of the human-computer system, all three aspects need to be optimized. In this series of four articles I want to pick up the topic of human performance at the computer, include new insights, and discuss performance-related issues that can be approached by UI designers. I will also devote an article to the concept of perceived performance.
In figure 1 below, I provide a schematic overview of the three above-mentioned performance aspects, the primary questions that are involved, and how these aspects are related to technology and UI design:
Figure 1: Overview of system performance, system responsiveness, and human performance and the related questions
For a more detailed discussion of the differences between the three above-mentioned aspects, see also my article The Three Pillars of Human Performance at the Computer – Which One Fits Best?
Having put together the different aspects of human performance at the computer and the questions that arise in this context, we can define a simple overall strategy for improving the performance of the human-computer system. Figure 2 presents the strategy as a diagram:
Figure 2: Overview of a general strategy to improve the performance of the man-computer system
In figure 2, I integrated performance aspects and related questions into a strategy that focuses on four aspects, only three of which are within the scope of UI designers:
Finally, I would like to extend figure 1 to indicate the directions in which the strategy described above might proceed:
Figure 3: Extension of figure 1 to indicate the directions in which the strategy might proceed
In the responsiveness area, we see that UI designers can come up with evaluations of waiting times that are based on the users' perception and reactions. Based on knowledge about users they can also give recommendations to the development and technical teams. The aspect of human performance is approached through the various facets of UI design and bears the danger of becoming huge and encompassing the whole UI design field. Performance-oriented guidelines can be a way to avoid this trap and to stay focused on performance-related UI design aspects.
To discuss some of the directions indicated in figure 3, this introductory article is accompanied by three further articles, which cover the following aspects:
We shall see that responsiveness and perceived performance methods are often closely related and difficult to keep apart. Nevertheless, these aspects are discussed in separate articles. Improving system performance, on the other hand, is beyond the scope of user interface designers and will therefore not be further discussed in this article series. Also note that the aspect of feedback in the event of delays (item 3 in the strategy) is covered in a separate series of articles (Waiting at the Computer: Busy Indicators and System Feedback).