The previous chapter dealt with how people typography affected how people interpret documents. This chapter continues in the same vein by looking at how people interpret graphics’ influence on how they interpret the overall document (Figure 1). As considered in this chapter, graphics are any visual element placed in a text, such as: tables, diagrams, graphs, and photographs. Use of graphics helps a person interpret a situation more quickly. However, even if people find information which is accurate and reliable, that information is essentially useless to those people unless they are able to interpret it and apply it to their current situation. “The power of a graph is its ability to enable one to take in the quantitative information, organize it, and see patterns and structure not readily revealed by other means of studying the data” (Cleveland & McGill, 1984, p. 535). Of course, the design teams must ensure the information presentation fits the people’s information needs.
TopBackground
I think it is important for software to avoiding imposing a cognitive style on workers and their work —Edward Tufte
Graphics in technical material rarely exist without text, and material with integrated text and graphics improves comprehension (Betrancourt & Bisseret, 1998). In a majority of HII situations, text and graphics appear within the same document; an assumption which will be explicitly covered in this chapter. Since graphics do not stand alone, it is important to consider how people interpret graphics, how text and graphics interact, and how together they affect communication.
Figure 1. HII model – Approaching graphical information
This chapter looks at:
Approaches to texts with graphical elements: Texts contain both text and graphics which people have to read and integrate together. However, images and text are mentally processed differently.
Types of graphics in technical documents: Reviews the major types of graphics and discusses the research finding on what makes that graphic type effective.
How people comprehend a graphic: Reviews what makes graphics work within a specific context and what factors interfere with interpreting the graphic.
TopIntroduction
Reading text is essentially a linear task of word recognition and then the word recognition builds to text comprehension via the construction-integration model described in Chapter 11: How people read. Reading text is fundamentally an unnatural communication method, while visuals evolved with humans interacting with their environment. Thus, since graphical communication is basically entirely visual, graphics have played an important role as user-interfaces changed from command-line to a GUI. Many people expected that “purely visual communication, without the use of words, could become an international auxiliary language…however, a purely graphic presentation does not usually catch the meaning of the information” (Garcia & Tissiani, 2003, p. 51). In the end, for communicating complex technical information and supporting HII, the use of graphics is extremely important, but much of the concrete information can only be communicated by text. Design teams need to be conscious of the best uses of both and how to merge them effectively.
Unlike text, comprehending graphics is multidimensional with the entire image being interpreted simultaneously. Multiple theories have been advanced about how graphics improve text comprehension and their rhetorical effect (Brasseur, 2003). Material gets presented twice (text and graphic) which leads to repetition of presentation and improved learning (Gyselinck & Tardieu, 1999).
Penrose and Seiford (1988) found over 50% of the users in their survey felt graphics were important to understanding a text. Likewise, texts with pictures consistently improve learning and comprehension over text-only texts (Betrancourt & Bisseret, 1998; Delp & Jones, 1996). These finding should not be surprising since text and graphics are cognitively processed in different channels and their dual nature should lead to better placement in long-term memory (Paivio, 1971; 1986).
The use of graphics on web pages and, to a lesser extent, in print, can be divided into three categories. This chapter is focused on the HII implications of the second item, content graphics.