The Vision Revolution: How the Latest Research Overturns Everything We Thought We Knew about Human Vision
by Mark Changizi
Benbella Books, 2009 ($24.95)

Ever wanted to feel like a superhero—able to read people’s emotions, see through objects and predict the future? Well, you’re in luck. According to Mark Changizi in The Vision Revolution, you can already perform all these feats—thanks to the exceptional power of your two eyes.

Changizi, a cognitive scientist at Rensselaer Polytechnic Institute, approaches the field of vision from a different perspective than most scientists do: he is interested not in how our eyes work but in why they work the way they do. Why, for instance, did primates evolve color vision, whereas other animals did not? Changizi argues that color vision did not evolve to help us pick out edible leaves or fruits—a theory that has held ground for decades—but rather that we began to see greens, blues, reds and yellows because doing so helped us to distinguish among hues of skin. Skin color changes slightly when we are happy, angry, embarrassed or sick, and our primate ancestors’ ability to detect these subtle changes helped them socially.

In case overturning one venerable hypothesis isn’t enough, Changizi offers more: for instance, our eyes face forward to help us see “through” objects, he argues. The fields of vision from each of our eyes overlap, so one eye can sometimes see behind an object when the other eye cannot. This overlap allows us to see layers in front of us. What is more, our eyes predict the future, he says. Imagine a game of catch: by the time your eyes process the sight of a ball a meter away flying toward you, it will already have passed you. We tend, then, to perceive moving objects as farther along their trajectories than they really are—a quirk that explains why so many visual illusions work the way they do, Changizi suggests.

Throughout the book, Changizi peppers his explanations with quick, fascinating visual exercises that help to drive his points home; these exercises are useful because his writing ranges from clear and engaging (and even quite funny!) to dense and somewhat abstruse at times. And although Changizi’s ideas sound radical—they are—he bolsters his arguments with evidence from many disciplines, among them neuroscience, evolutionary biology, medicine and linguistics. Still, the book leaves the reader feeling skeptical: Changizi’s theories are appealing and logical, and he backs them with good circumstantial evidence; however, as with any evolutionary theorizing, the ideas are also nearly impossible to prove correct—or incorrect. One thing is certain: The Vision Revolution will make you wonder the next time you notice someone blush, catch a ball or finish reading a magazine page. —Melinda Wenner


Finding Our Tongues: Mothers, Infants and the Origins of Language
by Dean Falk. Basic Books, 2009 ($26.95)


As far as we know, language is unique to humans. How and why it evolved has been debated fiercely for centuries. Now anthropologist Dean Falk presents a new theory: it was the tightening of our ancient ancestors’ birth canals when they began to walk upright that ultimately triggered the development of language.

As incredible as this hypothesis sounds, Finding Our Tongues builds a plausible case for it. Fossil evidence shows that as prehistoric moms began to live a vertical lifestyle, the anatomical rearrangement that accompanied it turned childbirth from a more or less breezy exercise into a risky ordeal that frequently ended in death. As a result, evolution favored smaller and more immature babies, Falk says. These little newborns were too weak and tiny to cling to their mother’s tummy as all other primates did. That is why mothers instead had to carry their little ones to maintain physical contact, which, much research shows, is what all babies want more than anything.

But this carrying posed a dilemma, because to gather food women had no choice but to lay their babies down. Deprived of the protection and comfort of their mother’s body, babies start to fuss. That fact, according to Falk, sowed the seeds for language because to maintain contact and soothe their kids, mothers invented the precursor to language: baby talk. “These vocalizations would have been the best way to sustain mother-infant bonds,” Falks says. Over millions of years the singsong babbling turned into full-fledged language, she claims.

Finding Our Tongues, though at times repetitive, ultimately provides a fresh and different perspective on language and its mysterious origins. Nevertheless, because Falk’s theory—like other theories on the origins of language—is based mainly on conjecture, the jury is still out on whether it actually was our ancestors’ changing anatomy that eventually compelled them to speak. —Nicole Branan