If you are worried that spending all day answering text messages and opening e-mails is making you dumber, you might be right.
In the last decade, high-tech brain scanning has shed new light on the mechanics of distraction - what happens when we shift attention frequently or let the mind wander. One thing has become certain: A person's attention is a limited resource.
Of course, distraction can have disastrous effects when you are behind the wheel of a car, but even multi-tasking at work can take a toll, robbing you of creativity and reflection, and depleting the willpower that might be needed later in the day to force yourself to the gym or avoid overeating.
Maggie Jackson, author of "Distracted,'' and a senior fellow at the New York-based think tank the Center for Talent Innovation, says the problem of workplace distraction is such a hot topic that some companies are beginning to experiment with "no e-mail Fridays.''
"A lot of people today are unhappy, overwhelmed, and feeling like they are knocking themselves out to get things done,'' Jackson says. "You are not able to use your higher order thinking skills when you are always distracted.''
In a 2011 survey conducted by Euro RSCG, an international communications company, 49 percent of the 7,000 respondents said that they worried that digital technology and multi-tasking were impairing their ability to think deeply and focus.
The brain is geared to novelty, which means that in some ways, it is seeking distraction, says Earl K. Miller, professor of neuroscience at the MIT Picower Institute for Learning and Memory. "Your brain is polling everything around you, noting what needs your attention.''
Miller led a 2007 electrophysiological study published in the journal Science that helped prove that we use one part of our brain to concentrate and another to be distracted. The prefrontal cortex, the brain's manager, resides directly behind the forehead.
It takes the lead when we are deliberately focusing on a project or goal. The parietal cortex, which is farther back in the brain, is always seeking sensory information from the environment.
"Things that are very loud or bright grab our attention,'' Miller says, because such abrupt changes in the environment could be signaling danger.
But often these lights and beeps are just announcing a new e-mail or text message. "If I have to sit and write a paper and these e-mails are up on the computer screen, I will be constantly looking over, changing my focus to what's not important,'' says Miller.
"The more gadgets we have seeking our attention, the more we tax our prefrontal cortex,'' he says. "You have a limited cognitive capacity to devote to your thoughts.''
The brain, like the rest of your body, runs on fuel. Every time you focus your attention, you use glucose and other metabolic resources, draining the supply.
Says Miller, "If you are fatigued, the prefrontal cortex is the first part of your brain to slow down.''
In a 2009 brain-imaging study published in the Proceedings of the National Academy of Sciences, John Gabrieli, a professor and neuroscientist at MIT's McGovern Institute for Brain Research, was part of a team that examined the brain's state when it is not specifically engaged in a task. That study focused on patients in the early stages of schizophrenia and their close relatives, but also showed how the average person's mind worked through the results of the control group.
For all study participants, the more active the mind-wandering regions of the brain were, the worse their ability was to do well at tasks.
"You can't be reminiscing or hoping what's going to happen tomorrow, and also paying powerful attention to what's actually going on,'' Gabrieli says.
A 2008 brain imaging study out of Carnegie Mellon University concluded that it wasn't just the hands-on nature of texting or dialing a cellphone that made driving dangerous, but the simple task of processing a conversation while trying to pay attention to the road.
Researchers collected MRI brain images of 29 undergraduates as they simulated steering a vehicle along a curved road while having to answer whether statements were true or false. The listening task reduced driving-related brain activity in the parietal lobe, where spatial processing takes place, by almost 40 percent, and the drivers hit simulated guardrails and had trouble staying in their lanes.
Every cognitive effort requires energy, says Mark Fenske, coauthor of "The Winner's Brain,'' and an associate professor of neuroscience at the University of Guelph in Canada. This brain fatigue often leads to failures of self-control, he says. "It's why you can mind your manners and control your temper at work, but when you come home, one little thing and you snap.''
It's also why you are likely to make better lifestyle decisions when your brain is better fueled, he says. "As in, do I eat the fries or the broccoli?''
Paul Hammerness, an assistant professor at Harvard University and a psychiatrist who specializes in treating patients with attention-deficit hyperactivity disorder, says the problem of inattention is a spectrum. "Everyone experiences these symptoms to a certain degree.''
He sees a lot of impulsivity in the way many people today respond to e-mails and text messages. "People need self-awareness. They need to tell themselves that they are going to sit down from 8 to 9 a.m. and work on one piece and not respond to a text or e-mail. They have to not let the environment dictate what they do.''
Hammerness, who coauthored the new book "Organize your Mind, Organize your Life,'' which offers solutions for dealing with the distractions, advises people to turn off the Internet connection and cellphone while trying to work. He also cautions against the temptation to do two things at once. "People think of multi-tasking as equally dividing up their attention across tasks with equal potency. Rather it is scattering attention and weakening it.''
Some interruptions and distractions are unavoidable, he adds, and emphasizes that it's important to be flexible. Some days mandate a necessary shift from one task to the other. "You need to be present in the moment,'' he says, and make conscious decisions about how you will apply your time and focus.
Jan Brogan can be reached at email@example.com.