The Buddhist idiom “monkey mind” does not require years of contemplation to understand. It explains itself quickly to anyone who attempts the most basic meditative practice: closing the eyes and concentrating solely on the breath. By the second or third exhalation, your attention will have shifted -- if not to an itch, or the aftertaste of your most recent meal, then to some memory, plan, song lyric, etc., and then to another, until you remember to focus on the flow of the breath.

Whereupon it will all start up again. The human mind, in the Buddha’s words, moves “just as a monkey swinging through the trees grabs one branch and lets it go, only to seize another….” The simile is all the more fitting given that he spent years meditating in the forest. (I take it by implication that the mind also makes shrill noises and scratches itself a lot.)

Twenty-five hundred years and a good deal of laboratory research later, Michael Corballis’s The Wandering Mind: What the Brain Does When You’re Not Looking (University of Chicago Press) has little to say about taming, much less transcending, the restless mind. Corballis, a professor emeritus of psychology at the University of Auckland, New Zealand, wants to reconcile us to the mental flux through a review of scientific research on the neurobiology behind ordinary awareness. From his perspective, wandering attention is necessary and even beneficial for humankind, in spite of the disapproval of authority figures for countless generations.

Central to the author’s approach is what he calls “mental time travel” -- meaning, in part, the human ability to remember the past and anticipate the future, but also (more importantly, perhaps) our capacity to shift attention away from immediate experience for considerable periods while focusing on our memories, plans and worries.

This power is a blessing and a curse, and Nietzsche suggested that it gives us reason to envy the beast of the field, which “springs around, eats, rests, digests, jumps up again, and so from morning to night and from day to day, with its likes and dislikes closely tied to the peg of the moment, and thus is neither melancholy nor weary.”

But that’s just human vanity talking. A variety of methods are available to record the flow of blood and bursts of neural activity within the brain -- and some can be used on lab animals as well as hospital patients. Corballis reports on experiments with rats that have learned their way through a maze to a feeding spot. The effort sets off “sharp-wave ripples” among the brain cells dedicated to tracking a rat’s location. But the activity may continue even after the rat is done, “as though the animal is mentally tracing out a trajectory in the maze,” the author says.

Perhaps this is not so surprising, since “for a laboratory rat, being in a maze is probably the most exciting event of the day.” But there’s more:

“These mental perambulations need not correspond to the paths that the rat actually traversed. Sometimes the ripples sweep out in a path that is precisely the reverse of the one the rat actually took. It may be a path corresponding to a section of the maze the rat didn’t even visit, or a shortcut between locations that wasn’t actually traversed. One interpretation is that the ripples function to consolidate the memory for the maze, laying down a memory for it that goes beyond experience, establishing a more extensive cognitive map for future use. But mind wandering and consolidation may be much the same thing. One reason that we daydream -- or even dream at night -- may be to strengthen memories of the past, and allow us, and the rat, to envisage future events.”

On that point, at least, our difference from the humble rodent is one of degree and not of kind: the human brain undertakes (and absorbs information from) a much wider range of activity, but the same part of the brain -- the hippocampus -- serves as the hub for the neural networks that enable “mental time travel.”

What does distinguish us, of course, is language, which among other things enables storytelling and more complex forms of social organization than those possible for even the most sophisticated chimpanzee community. So the human brain finds itself navigating any number of mazes, many of its own creation. Zoning out while someone is speaking, then, is not a solely a function of overburdened powers of attention reaching their limit. The wandering mind is part of a range of phenomena that includes dreaming, fantasy, hallucination and creativity -- all of them products of the brain’s constant obligation to shift between levels of experience and directions of “time travel.”

Corballis makes the point with a range of biological, medical and anthropological references in a casual style that sometimes just barely holds things together. One or two chapters might have been removed without it making much difference, as would the jocular bits about whether the reader is still paying attention. (“Yes,” reads my note in the margin, “because irritation wonderfully concentrates the mind.”)

While interesting on the whole, the book leaves completely unaddressed the question of whether there is any difference between a mind wandering under its own powers, so to speak, and one that’s grown accustomed to constantly increasing bombardment. Where the monkeys used to swing from vine to vine, they now run the risk of colliding in midair, distracted by all the beeps and buzzes coming from their smartphones.