Syntactic Analysis

This level investigates the extent to which diagram design allows viewers to perceive marks and to organize the marks into perceptual units. This analysis consists of three principles.

Principle 1: Perceptual Apprehension

Diagrams should be designed so that marks are easily perceived. This would allow viewers to see the visual message conveyed by each mark.

Only one diagram (Diagram 22b) violated this principle. In this diagram, arrows representing the Sun‘s rays (placed near a label ‗sunlight‘) are not clearly visible, and could be missed altogether. Without these arrows, it might be difficult to link the label ‗sunlight‘ with half of the Moon illuminated by the Sun‘s rays. Impact of this problem can be alleviated by using a modelling activity together with the diagram. The activity would show learners that the Sun‘s rays illuminate half of the Earth and the Moon at all times. Teachers who have no resources to model changing configurations of the components of the Earth-Moon-Sun system might have to draw a diagram showing that the Sun‘s rays illuminate halves of the Earth and the Moon. The fact that teachers have to make drawings in addition to the textbook diagram suggests that the diagram does not fully serve its intended purpose of visually presenting information.

Only one study has been found in literature, which reported problems of perceptual apprehension (i.e. Khanyane, 2002). Khanyane found that some information was difficult to see in a diagram illustrating causes of air pollution. Furthermore, she found that some captions were written in a font used in the text. As a result, the captions could not ‗stand out‘ from the text, and were thus difficult to see.

Principle 2 (Perceptual Organization)

Design of diagrams should enable viewers to perceive associated marks as linked. Several mechanisms can be used to help viewers to perceive marks as linked. These include continuity, proximity, similarity, framing, and use of arrows and numbers.

Only three diagrams violated this principle. Diagram 17 has two parts; the first illustrates four phases of the Moon while the second illustrates the Sun‘s rays, the Earth, and the Moon in eight positions around the Earth. No visual cues (e.g. numbering and labels) have been used to enable viewers to link the two parts of the diagram. Without this information, it might be difficult to get the complete message intended by artists of the diagram (e.g. seeing associated symbols as linked). Using a modelling activity together with this diagram can help learners to link the two components

of the diagram (to see which of the eight moon positions correspond to the four phases). If the diagram is the only visual aid available, then teachers would have to show learners which of the eight positions correspond to the four phases. Again, the diagram does not fully serve it purpose as it requires teachers to do what could have been easily illustrated on the diagram.

Diagrams 15b and 22b illustrate the Sun, the Earth, and the Moon in eight positions around the Earth. Artists of the diagrams used no mechanisms (e.g. arrows or numbering) to indicate that the Moon moves around the Earth. Without this information, it might be difficult to realize that the eight moon shapes form one perceptual unit, i.e. the Moon orbiting the Earth. This problem can be easily corrected by asking learners to add arrows or numbers to the diagrams.

Only one study reported problems of perceptual organization, i.e. in a diagram illustrating formation and breakdown of ozone molecules (Khanyane, 2002). The diagram had three components each with a caption. The captions were placed midway between the components, and no cues were provided to show that each caption belong to the figure above it. Khanyane speculated that this layout might confuse viewers. Furthermore, Khanyane found poor layout of information illustrating steps in formation of ozone molecules (the second component of the diagram). The sequence of these steps was not linear, but formed a c-shape. Khanyane speculated that this layout might confuse diagram viewers.

Principle 3 (Processing limitations)

Diagrams should be designed so that information can be processed without overloading working memory.

Books 1 to 10 have diagrams illustrating information in one perceptual unit (sequence of moon phases) while Books 11, 12 and 13 each has a diagram illustrating information in three perceptual units (the Earth, the Moon‘s orbit and phases of the Moon in Book 11, and the Earth, the Sun and moon phases in Diagrams 12 and 13). Books 14 to 24 have diagrams illustrating information in four perceptual units (the Earth, the Sun, the Moon‘s orbit and phases of the Moon). This shows that none of the diagrams analyzed in this study presented information in more than four perceptual units. This, in turn, suggests that information in the diagrams can be processed without overloading the working memory.

Although the diagrams analyzed in this study did not violate the third principle, research shows that some diagrams found in school textbooks present information in more than four perceptual groups, which can overload working memory. For example, du Plessis et al. (2003) found that a diagram illustrating the cardiac circle had two figures of the heart and several arrows indicating blood entering and leaving the heart. These arrows formed more than four perceptual groups. Furthermore, du Plessis et al. found that a flowchart illustrating thermal regulation had several concepts and arrows between the concepts, making more than four perceptual units. du Plessis et al. concluded that both diagrams were complicated. Thus, some school textbooks have complex diagrams, despite the fact that the diagrams analyzed in the current study had less than four perceptual groups.

Summary of syntactic analysis

The above discussion shows that only three diagrams (15b, 17 and 22b) had problems at a perceptual level. If these problems are not solved, learners would most likely encounter problems of obtaining the entire message intended by artists. That is, if viewers have a problem of accurately perceiving information, then interpretation of the information would be hindered.