Visual illusions are well-known in magic and popular culture, but there is a serious academic and research side to them, of interest to psychologists, neurophysiologists, optometrists and computer science specialists. This compendium brings together a wide range of current thinking and research on and into visual illusions, showing that the cross-disciplinary area has grown in recent years, building (in terms above all in computer technology applications and quantitative analysis) on many traditional insights and models from the past.
Formally recorded interest in visual illusions dates from before the early nineteenth century (as in Purkinje’s 1823 work on subjective visual illusions, but with precursors in Euclid and in Roman mosaics). Examples like the Delboeuf and Ebbinghaus illusions, both circle enigmas, and the Necker Cube, in both 2D and 3D, have fascinated and perplexed experts and the general public for centuries, and can be found across many cultural and scientific fields, from neuropsychology to art history. They are as much a problem in understanding geometrical and spatial designs (many with hidden elements) as they are in explaining subjective impressions and the functions of the eye itself. In seeing and making sense of what we see, we encounter challenges in knowing what is real, and how illusions and reality interact.
In trying to understand and explain visual illusions, then, we are dealing with complex relationships not only between the way we see and what is but also with light and colour, spatiality and virtuality, degrees of lightness and brightness, consciousness and cloze and representation. By this token, the compendium is aimed at a mainly specialist readership, in particular those readers with an interest in psychological, computer technology and neuroscience research and applications. It is a work for the research and academic collection, medical school libraries and where training is offered for professionals such as psychologists and psychiatrists. Yet, it is a work likely to interest the dedicated general science reader too, most probably consulted in a reference library (for topics like how do we understand shadows, recognise faces, imagine hidden images, make sense of blur and colour contrast).
The editors (Shapiro in psychology at the American University in Washington, and Todorović in psychology at the University of Belgrade) have coordinated the work of well over a hundred contributors from around the world, drawn from fields like ophthalmology and neural science, brain and cognitive science and artificial intelligence. The work is encyclopedic, with a companion website (noted above) where further (moving) images can be located: buying the book entitles purchasers to access to the website. In 115 separate chapters (all but a few original to this work), under 11 categorical themes (such as geometrical, brightness and lightness, faces, adaptation and attention), we are provided with a representative cross-section of current thinking and research. Many articles (many from funded research) revisit outstanding “problems” arising in visual illusion research, such as how we “see” (make sense of, try to reconcile with our knowledge of reality, impose false images on what we see), offering new explanations, some derived from advances in computer technology and the application of mathematical and statistical analysis.
Throughout there is a sure-footed awareness of how thinking has developed over the years, and this is supported not only by regular revisiting central issues but also by generous bibliographic support at the end of each chapter: this historiographic aspect of the compendium gives it special value. We move from general themes (perception and attention, humans and animals, humans and machines, light and space, false interpretations and deceptions) to specific geometrical examples like Müller-Lyer lines (which seem different but are the same length), ellipses and occlusions, why hills look steep, how we see leaning towers, how perspective and slopes can confuse and images that defy gravity. Such illusions are affected by luminance – brightness, lightness – and by colour, which often generates flicker and after-effects, where curves and compression and repetition operate, and we see surfaces that are “not there”.
It is when they move, when they are in motion, that even more complex effects are seen: stereoscopic images, binocular vision, rotation and tilting, check patterns and wagon-wheel designs, silhouettes and fast movement – all present challenges to the viewer and researcher. As a result, many of the chapters are recent reiterations and extensions of earlier research, carrying unanswered questions forward in new ways (and as a result, specialist users will examine each one to check its relevance to their own work). Many visual illusions are self-referentially ambiguous – they imply, wobble, blur, present counter-intuitive gaps and pseudo-images, and with all these the subjectivity of the onlooker and the physiology of vision itself as closely involved, and cannot be ignored as a key intervening variable.
There is an interesting section on face recognition, a field well documented in its own right. Some confusion arises from inattention, from the susceptibility of blind-spots in the eye, from binocular rivalry, from the speed with which we adapt to brightness or colour contrast, cope with the visual dissonance of conflicting images and understand moving and multi-sensory experiences. To sum up, the insights throughout the compendium are impressive and wide-ranging. The further readings provide pointers both for the generalist and the specialist (though ophthalmologists and computer technologists will, each in their own way, go to their own special sources). Images in black and white and colour are well-reproduced on the page and supported by website material. All in all, a timely and highly competent work.
