We are rarely conscious of the effort we expend shifting our eyes from one object to another. We can choose to move our eyes over a page, and yet once we engage whatever mechanism controls our eyes as we read, we are unaware of the workings of that mechanism and of the factors on the page (or in our minds) that control when and where we move our eyes.
Our eyes are, for most of us, the primary sensory organs that mediate between the world around us and the mind within us. And for psychologists, eye movements reflect the workings of a mind exploring its environment. By studying those movements, and the conditions under which they occur, we can better understand the workings of that mind.
Cognitive Processes in Eye Guidance is about the range of cognitive processes that control eye movements. It will likely become an indispensable research reference in support of the science of eye-movement control. Broadly, it divides its subject matter into eye movements during reading, during scene perception and during problem-solving. The one major omission is eye-movement control during language processing, but this is well represented by The Integration of Language, Vision and Action , edited by John Henderson and Fernanda Ferreira.
Cognitive Processes's sections on reading and scene perception are particularly useful because of the way they confront the controversies that abound in these two fields.
The first two chapters focus on different aspects and determinants of leftwards eye movements during reading; specifically, when they occur and to where they are directed. Some of these movements are quite short (to nearby text), but others are longer (and less accurate, relying on linguistic knowledge to help reconstruct where in the text to move to). The third and fourth chapters focus on the determinants of word skipping (which words we skip, and why) and how a word's structure determines where we land and how long we linger.
Each of these first chapters refers to contemporary models of eye-movement control in reading, and two distinct models are described in chapters five and six. The "E-Z reader" model assumes essentially sequential processing, from one word to the next; while the "competition/inhibition" model assumes parallel processing of a word and of previous/upcoming ones. The jury may be out on the "right" model or which features of each should be incorporated into a hybrid, but having these chapters side by side allows a reader better to assess the evidence for and against each model.
The next four chapters focus on eye movements during scene perception.
Again, although not all the contributors agree on which factors control such movements, presenting these differences side by side is valuable.
Chapter seven reviews how we extract the "gist" of a scene. Some of this work is presented in the context of how we relate captions to pictures, and how people divide their attention between the text and the picture. A particularly interesting issue introduced here is how attention to objects in a scene is determined by their surrounding context.
This theme is continued in chapter eight, which explores, among other things, how the viewer's expectations of what should be where can influence eye movements during exploration of real-world scenes. Chapter nine considers how information is maintained across eye movements (trans-saccadic memory). Contrary to much received wisdom, this chapter argues (probably correctly) that detailed visual information is maintained about one part of a visual scene when moving to another despite a range of phenomena, including change blindness (reduced sensitivity to changes in the scene that take place during a saccade), that suggest otherwise.
Chapter ten delves into the relationship between visual memory and eye-movement patterns (with the latter being predictive of the former).
Chapters 11 and 12 deal with somewhat similar issues but in different settings. Both concern visual search, with the former focusing on laboratory-based work and the latter on work "in the field" (or rather, on the road, while driving). The second of these chapters, being more applied, forms a useful bridge to the final three, which explore eye movements during game-playing (Tetris in one case, chess in the other) and insight problem-solving (cases where the answer "pops out" apparently with no explicit reasoning). In each case, eye-movement patterns allow the acquisition of information relevant to the perceptual encoding required to solve a task. By studying these patterns, one can identify the nature of the relevant encodings.
Each chapter has an informative abstract and an invaluable concluding section. Too many edited collections omit these sections, despite their obvious pedagogical value. The chapters are all readable, engaging and informative. This volume is a must-have for any researcher seeking a broad but in-depth review of the cognitive factors influencing eye-movement control.
Gerry Altmann is professor of psychology, University of York.
Cognitive Processes in Eye Guidance
Editor - Geoffrey Underwood
Publisher - Oxford University Press
Pages - 386
Price - £80.00 and £35.00
ISBN - 0 19 856680 8 and 856681 6