This is a quiet rejoinder to New Age wisdom-people are simply not designed to “live in the moment”-and the first part of “Chatter” grounds its argument in research about the brain. “We are perpetually slipping away from the present into the parallel, nonlinear world of our minds,” he writes our “default state” is a rich zone of remembrance, musing, projection. But Kross argues that self-talk has long been a part of humanity’s basic architecture.

“Chatter,” which spends a lot of time examining high-drama conversations that go nowhere, arrives as hundreds of millions of people broadcast their innermost thoughts (or what they’d like us to believe are their innermost thoughts) on social media every day. (The book’s subtitle-“The Voice in Our Head, Why It Matters, and How to Harness It”-reflects a slightly warmer attitude toward our inner cynic, who can also, Kross suggests, become our “best coach.”) It’s an irresistible thought experiment: What does yours look like? A drill sergeant? A languidly bored crush? Kross, who studies the “science of introspection” at the University of Michigan’s Emotion & Self-Control Lab, which he founded, aims to produce a different sort of portrait, one pieced together from MRI scans and clinical observations. This dope, or some form of him, is also the subject of “ Chatter,” a new book by the experimental psychologist Ethan Kross. (“Eat normal.”) He’s a nuisance, a torment, and not especially original-the kind of bargain-bin hater that makes all the rest of us critics look bad. “Ready for another disappointing day?” The camera follows the pair from the shower (“Your penis is very small”) to the car (“You know your dad hates you”) and then to work, where the dope, wearing a pin-striped olive jacket and gold chain, keeps the bit going through lunchtime. In “The Voice in Your Head,” a darkly comic short film by the writer-director Graham Parkes, a man wakes up every morning to find a fit, hipsterish dope perched next to his bed.

Chatter voice in your head