In her book On Looking: A Walker's Guide to the Art of Observation, Alexandra Horowitz shows how powerful observation can be.

Countless walks around the block with her dog inspired Alexandra Horowitz, a professor of animal behavior, psychology and cognitive science at Barnard College in New York, to inspect her daily peregrinations a little closer. She enlisted the help of experts whose jobs rely on the powers of perception and took 11 walks around Manhattan and its outskirts to see what she was missing. These journeys — as mundane as studying the markings of a single leaf or the striations of a rock — showed Horowitz that there’s more to the art of observation than meets the eye, which she articulates in her book On Looking: A Walker’s Guide to the Art of Observation (Scribner, $16), just released in paperback in April.

Horowitz, who already considered herself an expert observer by training, learned from her walking companions that a city block is a living, breathing being that can be examined under an infinite number of lenses. “As it turns out,” she writes, “I was missing pretty much everything.”

A stroll with her 19-month-old son ­reminded Horowitz of the joys of experimenting with the continually shifting properties of shadows, while geologist Sidney ­Horenstein demonstrated how a limestone’s variegated and worm-burrowed surface contains 400 million years of past life. And that’s to say nothing of the text Horowitz ­noticed jumping from all corners of her peripheral vision during her jaunt with typographer Paul Shaw. Together, they marveled at “long-legged R’s” and “high-waisted S’s” on storefronts and billboards. From walls laden with graffiti to words on manhole covers and errant potato-chip bags blowing down the street, Horowitz arrived at a startling conclusion: The world is awash in letters.

A blind world traveler and a sound designer for theater productions also guided Horowitz through journeys that expand the senses. Each roar of passing traffic and flap of a pigeon’s wings prove Horowitz’s hypothesis that a walk is nothing more than a selection among the countless stimuli bombarding you.

But if we’re a little dim-witted when it comes to truly seeing what’s around us, Horowitz says in her book, it’s not our fault. “Part of normal human development is learning to notice less than we are able to. The world is awash in details of color, form, sound — but to function, we have to ignore some of it.”