If you were to do nothing more than glance at the chapter names, you would consider this book to be a collection of occult dung powder. Old, stale, and reworked so often that it is dried up. The chapter titles are:
*) Color telepathy
*) X-ray vision
*) Future-seeing
*) Spirit-reading
However, that first impression would be a significantly wrong impression, Changizi has written such a fascinating and scientifically sound book that it remains interesting, even when you disagree with his conclusions.
The chapter "Color telepathy" describes how humans are often able to "read" a person's thoughts and diagnose the state of their health by interpreting slight changes in skin color due to the level of oxygenation in the blood. In this area, his reasoning is sound and Changizi points out that colorblind doctors have been demonstrated to be at a significant disadvantage when attempting to visually diagnose a patient. Where his reasoning breaks down is when he argues that Homo sapiens evolutionarily acquired color vision so that they could use changes in skin color to learn what other people were thinking. In my opinion, this position is untenable.
In general, predators try to blend into the environment as much as possible so that they can get as close as possible before they move in for the kill. Having an acute sense of color vision would allow the relatively defenseless human to spot the stalking predator much earlier than if they were colorblind. Although Changizi's position has some merit, the value of color vision in spotting predators is a much stronger argument for it being evolutionarily selected.
The chapter "X-ray vision" has nothing like the powers of Superman to see through solid objects, the point is quite different. In this context x-ray vision is a consequence of having two eyes with some distance of separation between them, allowing for the brain to receive two offset images. A consequence is that if a sufficiently slim object obstructs your view, while one eye may not be able to see a segment of the visual field, the other eye can, allowing you to "see through" the object. Changizi also convincingly argues why humans and other creatures evolutionarily kept both eyes pointing forward, gaining stereovision when looking forward while losing some ability to see behind them.
Chapter 3, "Future-seeing" is not ESP-style precognition but the processing similar to what we do when we catch a ball. As we prepare for the catch, our minds generate a prediction where the ball will be when it arrives, in other words we must compute the future position of the object. Several years ago, I read a book about baseball where it was stated that when a baseball is pitched at 90 miles per hour, it is physically impossible for the human eye to follow the trajectory for the last several feet. To hit the ball the batter must compute the best estimate as to where the ball will be when it crosses home plate.
In chapter four, "Spirit-reading", the author describes the role of written language, how it was developed and how it is used by the dead or otherwise distant to communicate detailed information to others. Once again, Changizi's analysis is sound; his description of minimal strokes and more complex ideograms as methods of communication was easy to follow and convincing.
It is clear that Changizi is an expert on the concept of how humans use vision to understand their literal place in the world and cope with the dynamic nature of their environment. As optical illusions demonstrate, human vision is a very complex apparatus and in this book Changizi clarifies a great deal in language that is accessible to everyone.
