In the weeks I spent listening to Malcolm Gladwell's podcast, I learned that lobsters have serotonin, that Elvis Presley suffered from parapraxis and that Mr. Gladwell adheres to a firm life rule that he drink only five liquids: water, tea, red wine, espresso and milk.

On the afternoon I met the author and journalist, I had just listened to an episode in which he interviews an intimidating guest. His audio recorder malfunctions, and he has to sprint to Staples to get a replacement. ''I was embarrassed,'' Mr. Gladwell confides in the podcast. ''I worried that he would think I was pathetic.'' It sounded mortifying. And yet when I sat down to interview Mr. Gladwell, at the kitchen table of his Manhattan apartment, I went ahead and trusted my own recorder.

This is what Mr. Gladwell, in his new book, ''Talking to Strangers,'' calls ''default to truth.'' Human beings are by nature trusting -- of people, technology, everything. Often, we're too trusting, with tragic results. But if we didn't suppress thoughts of worst-case scenarios, we'd never leave the house. We definitely wouldn't go on dating apps or invest in stocks or let our kids take gymnastics.

''It would be impossible!'' Mr. Gladwell said, throwing up his hands, almost giddy at imagining the social paralysis that would occur if we were a less trusting species. ''Everyone would withdraw their money from banks,'' he continued. ''In fact, the whole internet exists because people default to truth. Nothing is secure! They are hacking into the cloud as we speak!''

The ''default to truth'' theory is Mr. Gladwell's latest obsession and the theme of his first book in six years. Lots of readers will scoff. After his first two pop-science smash hits -- ''The Tipping Point'' (2000) and ''Blink'' (2005) -- Mr. Gladwell's reviews have steadily worsened, with prominent critics savaging his anecdote-heavy methodology. I counted myself among the skeptics. I doubted the premise of ''Talking to Strangers'' and dismissed it as armchair psychology.

And then my audio recorder broke midinterview, and I became a believer.

This wasn't just coincidence. It's exactly what Mr. Gladwell's towering success -- his five best-selling books, his six-figure speaking fees, his top-rated podcast -- rests on: the moment when the skeptic starts to think that maybe we're wrong about everything and maybe, just maybe, this Mr. Gladwell guy is onto something.

Nearly 20 years and millions of sales after his nonfiction debut, Mr. Gladwell is at something of a professional tipping point. He elicits from readers the kind of polarized reactions usually reserved for talk-radio hosts. To one camp, he is a master storyteller, pithily translating business concepts and behavioral science to a lay audience. To others, he is a faux intellectual, dressing up ordinary truths (such as an ''Outliers'' argument that success results from a combination of hard work and opportunity) as counterintuitive genius. How ''Talking to Strangers'' is received could cement Mr. Gladwell in one of those camps for good.

The book is weightier than his previous...