Peer into the windows of the soul

That the world looks to us the way it does is still a mysterious puzzle for vision scientists and all those who realise that there is much more to vision than meets the eye. The eyes are the portals through which we receive almost all information about the world around us, but the relationship between the visual information carried by photons of light and the resulting visual experience is not a simple one. The study of human vision is a rare example of an area of basic research that truly spans traditional disciplines, from the physics of light and the optics of the eye to the anatomy and physiology of the visual cortex and the psychology of sensation and perception.

Arne Valberg and James Enns have created two truly remarkable interdisciplinary textbooks of potential interest to students and instructors in the broadest range of subjects including computer science, medicine, linguistics, ophthalmology, optics, philosophy, physics and psychology. Both books argue against and debunk the view of vision as a passive, automatic process that results in a faithful record of the world in front of us. What is offered are two superb accounts of how visual experience, veridical and illusory alike, is a result of "seeing with the mind", a complex interaction between brain predispositions and the visual environment. They also address the relationship between neural activity and conscious experience, arguably the single most amazing aspect of vision, and how modern neuroscience has afforded new possibilities of experimental investigation of the question.

Light Vision Color is more technical and offers a detailed coverage of optics: the structure and behaviour of light as it interacts with surfaces in the environment, resulting in image formation in the eye. It will appeal to those interested in a more advanced and quantitatively based approach.

Coverage of the evolution of eyes is followed by the physiological characteristics of the eye structures and their relationship to neural signal generation. Wherever possible, the physiological aspects of activity and the activity of photoreceptors and other classes of retinal cells are linked to the perceptual experience of simple stimulus patterns.

Chapter four explores the "art of light measuring" and the sensitivity of the visual system in response to temporal and spatial stimulation. The impact of different types of vision loss such as age-related macular degeneration, cataract, glaucoma and retinitis pigmentosa on these functions is also considered. Chapters five and six deal with colour and can be considered the central chapters of this textbook. J. C. Maxwell's cited remark, "all vision is colour vision", captures the enthusiasm for colour in this book, colour being one of the most fascinating aspects of visual experience. Valberg discusses historical and more recent theoretical approaches to colour perception as well as the place the study of colour occupies in current neuroscience and neurophilosophy. It is through colour vision that we are shown how physics, psychophysics and neuroscience combine to unravel the characteristics of the visual experience of the external world and the neural and computational mechanisms underlying it.

It is also acknowledged that many phenomena and facts of colour vision including colour constancy, colour contrast and colour adaptation still await complete explanation, especially in terms of neurophysiology.

With an extensive coverage and glossary of technical terms, Light Vision Color is going to be a valuable resource for students and instructors alike, though it will be best suited for advanced undergraduate or postgraduate-level courses.

The Thinking Eye , the Seeing Brain covers an impressive array of complex issues in visual cognition and visual neuroscience in an accessible and compelling manner. It is an ideal book to achieve its stated aim of revolutionising students' thinking about vision, seeing and believing. It begins by asking the basic questions of why we have vision in the first place and how it can be studied scientifically. It goes on to consider how visual information is processed in different brain areas and the perceptual consequences of damage to different areas.

Chapters three, four and five deal with colour, contour and object perception respectively. They offer comprehensive and elegant coverage of a number of facets of visual processes, including colour impairment, veridical and illusory aspects of seeing colour, seeing contours where there are none in the image and the fascinating characteristics of the illusion of detail of our impressions of the visual world. These are profound and mind-changing phenomena that stand in contrast to common concepts of seeing. Chapter six deals with the almost always neglected temporal aspect of visual processing. It explores how various visual qualities such as motion or colour emerge over time and the consequences of differences in temporal dynamics associated with such processing. Illusions that arise from such "temporal chaos" are discussed, as well as how temporal binding of different attributes is achieved in the brain.

The "anti-gravity hills" and mystery spots where balls seem to roll uphill on their own are discussed in chapter seven. Here it is also shown that knowing which way is up and where we are heading is not as simple as it seems. Chapter eight explores how we become experts at certain types of visual processing, together with the role of visual imagery in visual processing. The final chapter discusses often counterintuitive, breathtaking and multifaceted aspects of visual awareness. These include neurological conditions such as split-brain patients, blindsight and Balint's syndrome that highlight the dissociation between vision for action and vision for conscious report.

In sum, this is an excellent book for both students and instructors in diverse areas of cognitive science and neuroscience.

Branka Spehar is senior lecturer in psychology, University of New South Wales, Sydney, Australia.