When the pressure's on before, say, a big presentation, there's a lot of anticipatory conversation — a stress rehearsal. Evan Steingart, former head of sales at a consumer-products company, worked with a salesman who rehearsed his entire pitch the day before he met with clients, including their objections in a different voice.

"It was an extreme distraction to the rest of the group," says Steingart. "People were so mesmerized by it."

They couldn't stop themselves from secretly dialing into the conference-room phone and listening in whenever he went there to practice. "Fortunately, he would always make the sale, and he never got into an argument with himself," adds Steingart.

For some, talking to oneself is a way to reach group consensus, sans group. Chris Weyers, who works for a financial-services company, talks himself up all day, he says, "as if someone is helping you get the day organized, urging you on to get things done faster, telling you not to check e-mail when you hear the ping."

He's more efficient, he adds, because "two heads are better than one." The problem is his assistant, whose hearing isn't what it once was, rushes in throughout the day, asking, "Are you talking to me?"

Many of us are as used to someone's self-chatter as we are to people with invisible cell-phone headsets seemingly blathering on to themselves. J.P. Tristani, a former commercial-airline pilot, flew with a DC-8 captain who, whenever faced with bad weather on radar, would "consult" aloud with an Indian chief he pretended sat in the jump seat behind him.

"I didn't care who he was talking to back there," he says, "as long as I didn't hear a voice coming out of that black void."

Self-talk can be both a cause of distraction in the office and its cure. After a while, you listen to yourself think aloud so you don't have to listen to the soliloquy next to you.

"Talking to yourself eliminates some other distractions," says J.J. Stives, who sat next to an incessant self-talker. His partner, Christine Ascherman, a commercial photographer, talks to herself about exposure and aperture before and during her shoots. "It wards off conversation," she says.

Carli Entin, an associate magazine editor, loves talking to herself whether it's "appearing" as a panelist on "Meet the Press," narrating her imaginary cooking show ("replace some of the water with coffee for a tastier cupcake") or blogging.

At work, even when a colleague told her she stopped listening, that didn't stop Entin's side of the conversation or the fun she had engaging in it. Besides, her self-chatter can be efficient. "By acting out the conversation," she says, "I no longer need to have it."