Author: Richard L Gregory
Publisher: Oxford University Press, 2009
Price: £16.99 (hardback)
Isbn: 9780192802859

People have long puzz­led over how our eyes and brains conjure images of the world around us. No philo­sophers’ or scientists’ theories have survived scrutiny. The author, a professor of neuro­psychology, tackles the problem by using illusions to give insight into how the visual process works. Hence the intentional ambiguity of the book’s title.

Gregory’s style is aphoristic rather than argumentative. After an overview of the problem (Locke and Berkeley get a look-in), he devotes a couple of chapters to the biology and evol­ution of eyes, which seem to have evolved from touch receptors. Evol­ution is emphasised throughout the book, since our eyes – and brains – evolved to aid our survival. He then goes on to classify illusions into a “Peeriodic Table” with six different types (blindness, ambiguity, instability, distortion, fiction and paradox), each of which is analysed and used to gain information on how the eye–brain process works. He emphasises that seeing is not a passive process, and that our brain’s interpret­ation of the world is probably more important. You don’t just see what’s there: you see what you think (or expect) is there. This is no surprise to forteans, who are well aware of the role expectation plays in visual reports.

The book is nicely laid out, with good illustrations, a useful index, copious notes and nearly a dozen pages of references. An version of his “Peeriodic Table” expanded as an appendix summar­ises the main points.

There are some very thoughtful insights in this book, but one is left frustrated by how little is understood even after so much research.