Sex Sleep Eat Drink Dream (6 page)

Francis Crick and Christof Koch suggest that our ability to take conscious notice of an event has to do with the way attention influences the coalitions of neurons responding to various sensory stimuli—the deer by the highway, the distant whine of a siren, the naked bather. These coalitions vary in size and character, Crick and Koch suggest; they form, grow, compete with one another, disappear, or endure in fluid response to changing situations. Only those that are sustained make their way into consciousness as a registered perception. Attention, the theory goes, somehow serves to determine which rival coalitions win the competition. Perhaps attention jacks up the neural activity in one coalition by firing a certain way, making the stimulus that activated that coalition seem bigger and brighter than those activated by competing stimuli. In this view, attention not only points a finger at a sensory experience, it
makes
the experience.

Even when we think we're fully attending, we may miss critical particulars. Imagine this challenge: As a rapid stream of numbers flash by, pick out the two letters among them that appear randomly for only a tenth of a second. How would you do? Chances are you'd pick out the first target letter, but if the second appeared within a half second of the first, you'd fail to see it. This is because of a weird neural bottleneck—an attentional "blink" that prevents you from consciously attending to multiple visual events so close together in time.

Which begs the question: V/hat happens when we try to attend to two things at once?

***

For years my mother shuttled my profoundly retarded sister back and forth to her special school—a tediously long, twice-daily commute. While she navigated the Virginia highways, she would drink a cup of coffee and memorize poetry from a book propped up on her dashboard. For her, such juggling of Sumatra, steering, and Wallace Stevens was a kind of mental necessity to keep her mind nimble during the numbingly long drives. But most of us multitask out of an obsession with making the most of our time: We listen to the radio while reading the newspaper; we pay bills while chatting on the phone and type text messages while sitting in meetings.

How efficient is this? Are we doing both jobs justice? Are we saving time?

"To do two things at once is to do neither," wrote Publilius Syrus in
A.D.
100. Evidence is building to support the Latin poet. Despite the massive parallel-processing capabilities of its one hundred billion neurons, the brain just isn't built for two-timing. In attempting two tasks at once, it can be foiled by even the simplest jobs.

Take the matter of gauging how much time you have before the signal light ahead switches from yellow to red. To brake or sail through? The answer depends in part on your interval timer, another clock possessed by your brain. This one is expert at gauging the passage of time from seconds to minutes and hours. We tend to have pretty good interval sense when we're paying full attention—accurate to within 15 percent—and use it to make decisions and judgments in all sorts of everyday situations: running to catch a bus or a baseball, singing along with Regina Spektor, keying in a number on a cell phone while glancing up periodically to check the road. But as science has discovered, this internal timer suffers mightily from distraction.

Just how our brain calculates time intervals has been one of the most elusive concepts in neurobiology. Unlike seeing or hearing or smelling, interval timing has no dedicated sensors, as Richard Ivry, a cognitive neuroscientist at the University of California, Berkeley, points out; nonetheless, it's as "perceptually salient as the color of an apple or the timbre of a tuba," he says, and we need it for driving, walking, conversing, playing music, participating in sports, and a million other daily activities. For years scientists thought that the interval timer was located in some central hourglass area of the brain, inspired, perhaps, by the discovery of the circadian master clock in the SCN. But new research indicates that the brain may judge intervals through the activity of a network of neurons widely scattered among many different brain structures—and that different time intervals may be processed by different neuronal networks. Ivry's work suggests that the cerebellum, the part of the brain that coordinates movement, plays a role in the timing of tasks in the range of milliseconds. For longer intervals such as timing a yellow-to-red stoplight, the brain most likely uses a more distributed system, says Ivry, involving structures active in working memory, such as the prefrontal cortex and basal ganglia.

Temperature may toy with this clock, disrupting our ability to accurately time intervals that span more than a second. A doctor discovered this when his wife was ill with a high fever. He rushed out to the drugstore to get her some medication; when he returned twenty minutes later, she was upset with him for taking so long, claiming that he had been gone for hours. Intrigued by her misperception of passing time, the good doctor asked her to estimate a minute by counting to sixty at one number per second. Her estimate turned out to be thirty seconds long. As her temperature fell, her performance improved.

However, nothing flummoxes our interval timers like distraction. When participants in one study were asked to assess intervals of fifteen to sixty seconds while they performed concurrent real-life tasks, their accuracy plummeted. When you're engaged in one thing, time expands. When you're dual-tasking, it contracts; the brain misses the metaphorical "tick" of some number of pulses, so time seems shorter. It's simple: Accurate judgment of time requires attention to its passage—of critical import in matters of traffic. This is one reason why driving and chatting on a cell phone is not a good idea. There are others.

I'm no good at multitasking. When I talk on the phone, I can't hear my husband's verbal prompts or read his written ones. I can't drive and change a CD, much less memorize poetry. Not long ago, at a psychology lab at the University of Virginia, I had my inadequacies officially documented. But I also learned that I'm not alone in my "disability": Most people overestimate their capacity to attend to two things at once—especially when they're driving—with consequences that range from annoying to catastrophic.

"What do you get when you cross an owl with a goat?" This was the riddle posed to me the day before by Bryan, the first-grader I tutor in reading, and his teacher. Only later, in the small basement room of the Cognitive Aging Laboratory, was the answer percolating—when my mind should have been on the task at hand. My mission: to write down all the words I could think of in one minute that begin with the letters
f, a,
and
s
. I got started with a few familiar verbs and objects—animals, furniture, fruits—but then stopped. F? S? My mind suddenly locked up. Words starting with a? I couldn't think of a single one. Then "agoraphobic" popped out of the box, and "soporific" and "flagrant" and "felicitous." I was keenly aware that these long Latinate adjectives were wasteful luxuries; I should stick with the Anglo-Saxon, the monosyllabic—the sip, sap, soap; the flea, fly, and feel. My back muscles tightened, my hands grew clammy. I tried to think of the
fl
consonant blends I had supplied to Bryan—flip, flop, flap. Then the riddle seeped into consciousness to steal my attention.

Hootenanny.

That Bryan could appreciate such wordplay struck me as a small miracle. One of the many children who for one reason or another are deemed "at risk," Bryan had come to town only a few months earlier with his mother and older sister and virtually nothing else but the clothes on his back and a particular shade of sweetness that made teachers, librarians, and custodians silently mouth at me as we passed in the school halls, "I love that kid." When Bryan arrived, he had struggled with the very basics of language, with rhymes and phonemes, those sound packages that make up words. Just a few days earlier he had stumbled on a word that stumped him. "Wish?" he inquired. "What's a wish?"

The question had stunned me. Think of the myriad folk- and fairy tales most of us encounter in childhood, of wishes granted and often squandered by luckless recipients: Cinderella, the Frog King, the Seven Ravens, and of course the Grimm brothers' Three Wishes, a story I remember first reading when I was Bryan's age. After a minor bout of misbehavior and subsequent punishment, I had sought refuge with my book of fairy tales in my parents' clothes closet, dimly lit by a small circular window and redolent of shoe polish, mothballs, and my father's after-shave. I remember especially the image of the wished-for sausages stuck on the nose of the poor wife, with only a single wish to go.

Somehow, in the midst of all his want, Bryan had missed the concept of wish. I had asked him to tell me his big three. "I
wish
for a Popsicle. I
wish
for new sneakers. I
wish
for a remote-control car." He paused for a minute, then grinned at me and sang out, "WISH, FISH, DISH, PISH, MISH!" That Bryan could come so far in such a short time, to get the puns and verbal jousting, was humbling testimony to his powers of focus and concentration.

My minute was up. I flashed a smile of chagrin at the twenty-something graduate student administering the test. He seemed to have little sympathy. There it was in raw data: The split attention of this writer yielded an abysmally poor score on, of all things, verbal fluency.

The fluency task was the first of a dozen or so cognitive tests I would take over the next several hours as a participant in a study of the brain and its workings by Tim Salthouse, the director of the laboratory. Though the setting was artificial and the tasks contrived, I could see how these tests were aimed at parsing the things our brains do on a daily basis. They are windows on how we think—specifically, how our brain accomplishes its repertoire of organizing activities, called executive functions: focusing attention, concentrating on what's relevant and ignoring what's not; making split-second decisions, often based on conflicting information; shifting mental goals and rules in the face of new demands; doing two mental jobs at once.

Among the trials were classic tests of dual-tasking: steering the wheel of a driving simulator to keep a tracking ball between two wiggly, swerving lines while counting backward by threes from 862; and the Stroop test, a list of color names presented in mismatched ink (the word "blue," for instance, printed in red). The subject is expected to quickly reel off the names of the printed colors, not the words.

My performance on both Stroop and simulator was pathetic—though, it turns out, not all that much worse than the average. Teens who play video games are sometimes pretty good at the simulator task, but the Stroop test often stumps even the young. Because reading is more automatic than recognizing and naming colors, speed in this test requires focusing attention only on the color of the typeface and simultaneously inhibiting the desire to read its verbal content. Try it yourself; it takes longer to say "red" to the word "blue" printed in red than to say the word "red" printed in red, because two mental processes are in conflict. (Rumor has it that the CIA used the Stroop test in the 1950s to ferret out Russian spies. The names of the colors were written in Russian; if test participants were slowed by the written words, it was a sign they knew the language and might be spies.)

People's ability to dual-task is a good deal less impressive than they think, in part because of the limitations of working memory. If you can recall the start of this sentence while you read the end, you can thank your working memory. Also known as short-term or scratchpad memory, it's what allows you to keep in mind several facts or thoughts (most people can hold between five and nine) and manipulate them for a brief time, a few seconds or so, while solving a problem or performing a task: holding in mind a phone number, for instance, or remembering where you are in the subtraction part of your simulator task, or recalling how long it normally takes for a traffic light to turn while deciding to brake or accelerate.

When you try to carry on a cell phone conversation and stay on the road, tuned to traffic, you strain your working memory as well as other executive functions, such as the ability to shift goals in your mind, activate new rules, and refocus your attention.

To quantify just how efficiently the brain toggles between two mental jobs, David E. Meyer and his colleagues at the University of Michigan asked a group of participants to perform two tests of dual-tasking. In the first, they were asked to switch repeatedly between a pair of tasks focused on geometric shapes, judging one perceptual characteristic (shape, for instance) and another (color, size, or number); in the second, between two tasks involving different kinds of arithmetic problems (say, switching back and forth between multiplication and division). In both tests, the participants took more time to complete the tasks simultaneously than they would have if they had performed the tasks one after the other. "Sometimes they showed an increase in total task completion time of 50 percent or more," says Meyer. That's because the brain takes time to shift its mental rules and goals, he explains, to leap from "I'm doing this, which requires these rules, to I'm doing that, which requires those rules"—several tenths of a second, in fact, which adds up if you're toggling a lot.

When you're on the cell phone and the vehicle you're driving is moving along at eighty-eight feet per second, those lost moments may mean the difference between life and death. According to a 2006 study by the National Highway Traffic Safety Administration, some 80 percent of crashes and 65 percent of near crashes have involved some form of driver inattention less than three seconds before the event. Talking on a cell phone increased the risk of a crash or near crash by 1.3 times; dialing a cell phone tripled the risk.

***

It's 10
A.M.
You've reached the office safely and swallowed a second cup of coffee while returning phone calls and e-mail. In another hour or so you're expected to give a presentation at a meeting. Now you plunge into the required reading, all fine focus and concentration. If we could eye the workings of your gray matter as you scan those pages of dense text, what would we see? What's going on beneath the snug carapace of your skull while you engage in keen-witted reading (or, for that matter, its nemesis, distraction)? Until lately, the brain and all that it lodged—the ability to think, feel, act, imagine, reason, remember—were one dark riddle. But in the past decade, science has opened stunning new windows that allow a look inside to see in detail a brain going about its business in real time.