Oh, dear. Something else to worry about.Cellphones may cause brain cancer. “May” is the key word in that sentence, as in “maybe,” “possibly” or perhaps even “not likely.” The International Agency for Research on Cancer, a branch of the World Health Organization, has not concluded that cellphones do lead to brain cancer, but that “we need to keep a close watch for a link between cellphones and cancer risk.”

Cellphones join a list of 32 things beginning with the letter C that are possibly carcinogenic to humans, including coffee, carpentry, coconut oil in shampoo and carrageenan, a thickener found in instant-pudding mixes. You’ll be happy to know that cookies and cupcakes are not on the list. Yet.

Science ultimately may be able to prove whether or not you risk your health by using a cellphone. But science has already proved something else about cellphones: They are really annoying.

Cellphones give us intimate and frequently unwanted insights into the lives of others. Is it really necessary to learn the details of a recent colonoscopy from the diner sitting at the next table in a restaurant? It may seem that cellphones annoy us simply because we think someone talking loudly in a public setting, especially to an invisible companion, is rude. But our reaction may also be biological.

In fact, brain science may explain why we are annoyed by lots of the small disturbances of daily life. We humans are programmed to impose order on ourselves; we get annoyed when the unpredictable messes up that program. And while many of our annoyances are highly idiosyncratic and individualized, cellphone chatter is a universal irritant, transcending race, age, gender and culture.

Psychologist Lauren Emberson’s research suggests that the way our brains process speech affects how we feel when we hear these one-sided conversations. She became interested in the question of why cellphones annoy while living in Vancouver, where she had a 45-minute bus ride to school each day. During her commute, she wanted to read essays on the philosophy of the mind, but she found herself distracted by her fellow passengers’ phone conversations. At first, she thought her distraction was “because I was nosy,” she says. “But I actually didn’t want to listen. I felt myself forced to, almost.”

After studying the issue, she’s concluded that when we hear half of a conversation, or a “halfalogue” — such as when someone is talking on a cellphone — “our brains are always predicting what’s going to happen next, based on our current state of knowledge. . . . When something is unexpected, it draws our attention in, our brains tune in to it.”

Speech, especially, reels us in. Listening to it, our brains are not passively soaking up words like a sponge — they’re actively trying to predict what’s coming next, to make it easier to make meaning from conversation. You may be able to finish your spouse’s sentences, but your mind wants to finish everyone else’s sentences, too.

There’s plenty of evidence that humans are good at filling in the blanks. One example is what’s called verbal shadowing. “The task is to listen to someone speaking and repeat what they say as soon as possible after they say it,” says University of Pennsylvania linguist Mark Liberman. “There used to be people who would go on variety shows because they could do it almost as fast as the person was talking. They hardly seemed to be behind them at all.” The brain has developed to make sense of the world in real time, even as it changes.

Even people without any special skills can do this fairly rapidly, but only when the speech is logical. Ask them to shadow someone reciting nonsense phrases, and everything slows down, studies show. And then people get annoyed.

Emberson has shown that halfalogues distract us more than dialogues or monologues do. In one study, she and her colleagues asked people to perform a task that required a lot of attention: using a mouse to keep a cursor on a dot that was moving around a computer screen. The researchers wanted to know if people were worse at this when overhearing halfalogues.

Indeed, people started to make more errors moments after the halfalogue commenced. “When the person starts talking, your attention is really drawn in,” Emberson says. “It’s really automatic.”

To make sure that the effect was caused specifically by understandable speech, Emberson then filtered the halfalogue so that it was garbled and unrecognizable as words. In that case, the distracting effects went away.

Her theory is that because our brains have to work harder to predict speech when we’re hearing only half a conversation, we divert more attention to it and get more distracted from what we actually want to be doing. Annoyance ensues.

Although cellphones are fairly new, halfalogues are not a new irritant. More than a century ago, when good old-fashioned land lines were coming in vogue, Mark Twain railed against halfalogues in “A Telephonic Conversation” in the Atlantic in June 1880:

“You hear questions asked; you don’t hear the answer. You hear invitations given; you hear no thanks in return. You have listening pauses of dead silence, followed by apparently irrelevant and unjustifiable exclamations of glad surprise or sorrow or dismay. You can’t make head or tail of the talk, because you never hear anything that the person at the other end of the wire says.”

Lucky for Twain he didn’t live to see the cellphone. At least the phone cord once tethered us to our desks or kitchens or phone booths. Now people are free to roam. Restaurants, waiting rooms, bathrooms, gyms, even libraries are fair game for the modern communicator.

There’s a chance that cellphone conversations will eventually fade into the noise tapestry of life. If everybody is yakking all the time, it’s unlikely that our overworked brains will be able to track a multitude of halfalogues simultaneously.

But even if we do manage to tune out cellphones, the multitude of other annoyances will still be waiting. Why do the little things bother us? You might think scientists would have a ready answer, since annoyance is one of the most recognizable human emotions. But with a few notable exceptions, they don’t.

So it fell to us, two science journalists, to try to generalize what can be learned from the cellphone research, as well as from studies in a variety of other fields, including physics, psychology, acoustics, ethology, chemistry and linguistics, to define what makes something annoying.

Our conclusion: Things that are annoying have three basic components. First, they are unpredictable, or at the very least unavoidable. You might know that the Mixing Bowl in Springfield will be snarled at rush hour, but there’s not much you can do about it.

Second, they are unpleasant (but not harmful — annoyances are, by definition, trivial). There are few universals in this category: the sound of fingernails on a blackboard or the smell of rotten eggs may qualify — or, of course, halfalogues — but not many more. Poor grammar may not bother you, but it makes some people nuts. Noisy eaters drive other people bonkers. Still others can’t stand it when people wear too much cologne.

Third, annoying things are of uncertain duration. You know they will end, but you don’t know when. This allows time for recursive annoyance, also known as terminal annoyance, where you become annoyed with yourself for being annoyed.

There’s one paradoxical quality of annoyances that we still don’t quite understand: Nobody likes to experience them, but everybody seems to like to talk about them. It’s as if they give us an excuse for a community catharsis, all of us railing together against aggressive drivers, pointless red tape and that guy on the Metro clipping his nails.

All of these things can drive you nuts, but they’re unlikely to end up on anybody’s list of potential carcinogens.

doctorannoyng@gmail.com

flora.lichtman@gmail.com

Joe Palca is an NPR science correspondent. Flora Lichtman is multimedia editor for the public radio program “Science Friday.” They are the authors of “Annoying: The Science of What Bugs Us.”

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