Representational/Photorealistic imagesInstructional pictures have been classified into three types, on the basis of how they convey meaning:
Much research has evolved from the use of photorealistic images to assist learning in text-based situations. Several experiments investigating the effects of realism have been carried out (Dwyer, 1970; Dwyer and Joseph; 1984 and references therein). The results showed that the effectiveness of realism is directly proportional to the time and effort put into studying the images. Students working at their own pace (self-paced learning) took most advantage of the information provided in realistic images. However, if the time the student has for study is short and under control then line drawings (simple representations) proved to be most effective.
There is also the danger that complicated realistic images may distract the student and impede learning (Holliday and Thursby, 1977). This is an important point when teaching students who have a low aptitude for the subject.
These last points lead us to the obvious question:What is the objective of the illustrations used?
The learning objective that the author is aiming to achieve must always be considered. Realistic images may motivate students more than line diagrams. They may gain the interest and attention of learners by adding variety or providing a focus. Myatt and Carter (1979) and Spaulding (1955) reported that students appreciated more realistic images and detailed pictures. Of more importance is the fact that photorealistic images, particularly moving ones, may help aid understanding and learning of concepts that cannot be explained verbally or for learners with a low degree of verbal understanding.
Placement of images in computer-based learning materialBernard (1990) stresses the importance of placing the image near the text that it supports or making obvious the links between image and text. Often this is difficult if the size of the computer image is full screen. Therefore, use quarter screen images when available. Images related to text should not be put on a second "page" of the module. That is, the text and associated image must appear together (there is no reason why the image should not appear on a second monitor as occurs with two-screen videodisc programs, although this may carry an extra overhead in terms of additional software and hardware costs). If necessary place a "button" on the screen that when pressed causes the appropriate image to appear. Several images can be used in this way but this can lead to problems with colour corruption of subsequent images (see section on palettes for further details). With printed material the need to turn several pages to find the relevant diagram can be distracting (Hutchinson, 1990).
Opinions differ as to whether images should be placed to the left or right, or above or below, any text. The computer-based education section of Queensland University of Technology suggests that the illustrations should appear towards the upper left hand corner of the screen. The reasons for this are that the eye automatically scans from left to right and any image, regardless of its placement, will gain the attention of the learner (Russell and Redhead, 1991). However, preliminary observations at Bristol University have shown that users are likely to spend more time observing and analysing the images and associated text if the image appears towards the right side or below the text. The user reads some text, refers to the image, refers back to the text and so on. When images were placed to the left or above the text, users quickly passed over the image onto the text and rest of the screen without referring back to the image (personal observations made during staff development workshops).
On occasions almost the entire screen will be taken up with an illustration. In these instances the centre of the screen is not necessarily the best position for the image. Good design practice is to place the image's focal point slightly off centre.