Eye Movement Recording
Searching for a Name
Positioning of Type
Eye movement recording is a useful technique for studying map reading behaviour but its application is much more limited than is generally realised. The difficulty arises mostly from the disparity between fixation and attention. Eye movement apparatus tells us, to a limited accuracy, the position on the map which is being fixated. But the map symbol which is actually being attended to may be some distance away from this spot. Because maps are so densely packed with information, there may be many symbols close to the fixation spot and without further information it is impossible to say which of these is actually being processed.
The disparity between fixation and attention may be quite large for symbols such as colour codes which can be processed several degrees of visual angle away from the fovea, but typographical symbols (e.g. place names) must fall close to the fovea if they are to be read. For this reason eye movement recording is especially informative for studying map typography and two studies on this topic are summarised below. There is also another section devoted specifically to map typography.
Some use of eye movement recording is also used in one experiment in Colour vs. Visual Texture for Area Symbols.
Phillips, R. J. (1981). Searching for a target in a random arrangement of names: an eye fixation analysis. Canadian Journal of Psychology 35 (4) 330- 346.
Abstract - Four experiments investigated the eye fixations used in searching for names in map-like displays. A typical display was a random arrangement of 20 names all of which were in the same type style and point size. Compared to data from searching for symbols, two differences emerged. Firstly, there was little or no tendency to fixate names which resembled the target. When subjects moved their eyes, they simply fixated one of the nearest names which had not been fixated before, often following a search path characteristic of the individual. Secondly, fixation times were not constant, but were consistently longer on names which resembled the target, for example, fixations on names with the same initial as the target were considerably longer than on names with a different initial. Fixation times were also longer on displays with names set in a small type size. Peripheral vision is important in placing fixations but, from tachistoscopic evidence, it is clear that information which is potentially available in peripheral vision is not always used when searching. The strategies available to the searcher are discussed, and practical implications for map design are considered.
Full paper as pdf file (1656KB).
Noyes, L. (1980). The positioning of type on maps: the effect of surrounding material on word recognition time. Human Factors, 22, 353-360.
Abstract - Two visual search experiments, one of which measured eye movements, show that material close to words on a map-like display has a proximity effect which prolongs the word recognition time. This effect is particularly pronounced if the material is, a) very close to the first letter of the word, and b) of a similar size to the word, or component letters. Possible causes of the effect are discussed and the practical application for maps and other displays considered.
Full paper as pdf file (782KB).