Section 1: Images and learning
Images have a direct route to long-term memoryCurrent studies of human memory make a functional division of memory into short-term and long-term memory. Both types store and remember information as "chunks" but there is a difference in the number of chunks that can be retained and recalled. Immediate or short-term memory can only retrieve a limited number of items at a time - roughly seven plus or minus two. Long-term memory on the other hand does not seem to be limited to a finite number of chunks or concepts that can be stored and retrieved (Miller, 1956; Gage and Berliner, 1988).
A number of experiments carried out in the 1970s showed that not only does the brain have an extraordinary capacity to imprint and recall, but that it can do so with no loss of memory. The capacity for recognition memory for pictures is limitless. Pictures have a direct route to long-term memory, each image storing its own information as a coherent "chunk" or concept (Paivio et al., 1968; Standing et al., 1970; Paivio, 1971; Standing, 1973; Paivio, 1975; Erdelyi and Stein, 1981 and references therein). However, the images or pictures must be meaningful to be retained (Freedman and Haber, 1974).
Being non-text intensive, the computer environment is ideal for the use of images to enhance learning. Pictures make use of a massive range of cortical skills: colour, form, line dimension, texture, visual rhythm and especially imagination (Buzan, 1990). Imagination comes from the Latin imaginare, meaning "to picture mentally". Images are generally more evocative than words and more precise in triggering a wide range of associations, enhancing creative thinking and memory.
Alesandrini (1984) in a survey of American commercial educational courseware found a low rate of use of graphics. There may be several reasons for this: a low level of understanding of the use of pictures among designers; designers may see graphics as an added extra and not central to the design and learning process; overemphasis on the word as the primary vehicle of information; resources of suitable images in computer useable form may be unavailable or have copyright restrictions or in the case of computer-based courseware graphic displays may not have been capable of achieving the results needed. Today, with good computer graphic capabilities, high quality photo-realistic images can be achieved.
With a more complete understanding of how the mind works we are beginning to realise that a new balance must be established between the use of images and the use of words. The brain is divided into two hemispheres, left and right. Both gather in the same sensory information but each half handles the information, or parts of the information differently. The left side, or logical left as it is known, is the analytical, verbal, sequential, symbolic, linear half. The right side allows us to have imagination, visualisation, understand metaphors and create new combinations of ideas; it is more spatial, holistic and relational (Edwards, 1982).
The computer industry makes use of this knowledge and this is reflected in the increasing development of machines that allow us to link and manipulate words and images together (Buzan, 1990). It is important, however, that any visual material is used in the correct manner (see next section).
There is considerable evidence that users find reading text from screens more difficult than from printed material (Gould et al, 1987; and references therein). The computer screen, however, is not a text-intensive medium (at least it should not be, if proper screen design guidelines are practised); thus the replacement of text, wholly or in part, by illustrations is important.
There is also evidence that text should sometimes be used to support pictures as well as the converse (Holliday, 1976; Weidenmann, 1989; Bernard, 1990). Bernard (1990) went on to consider two strategies for increasing the effectiveness of illustrations in text. Two types of caption were used:
In general, users prefer material which is illustrated (Levie and Lentz, 1982) and regard it as being of higher quality. Levin (1989) states "pictures interact with text to produce levels of comprehension and memory that can exceed what is produced by text alone." It may well be that many of the findings from studies of the use of illustrations in printed material are transferable to the computer screen. Below are some of the points and guidelines summarised by Levie and Lentz (1982) in an extensive review (153 experiments) of the effects of illustrated text against text alone.