We all know the expression "To err is human." And this is true enough. When something goes wrong, the cause is overwhelmingly attributable to human error: airplane crashes (70 percent), car wrecks (90 percent), workplace accidents (90 percent). Once a human is blamed, the inquiry usually stops there. But it shouldn't—not if we want to eliminate the mistake.
We're all affected by certain biases in the way we see, remember, and perceive the world, and these biases make us prone to commit certain types of errors. As a journalist who's spent years studying the science of human error, I've identified common mistakes that afflict us all. Here are seven, along with ways to avoid making them in the first place.
1. We make slips of the tongue.
There is a mistake committed by people of all ages and cultures: We fail to come up with the name of a person we know or, even more embarrassing, we call the person by the wrong name. Researchers call these gaffes slip-of-the-tongue or tip-of-the-tongue errors, or TOTs, for short. For most people, they occur about once a week.
One of the more infamous slips occurred just before the 1992 Super Bowl. Joe Theismann, a former quarterback for the Washington Redskins, was interviewed by two reporters about Redskins coach Joe Gibbs. Gibbs was, and still is, considered one of the finest offensive strategists. The reporters wanted to know whether Theismann thought Gibbs was a genius.
Theismann didn't think so. In the first place, he said, the word genius isn't applicable to a sport like football. Added Theismann, "A genius is a guy like Norman Einstein."
Norman Einstein? Clearly Theismann meant to say Albert Einstein. Too late. His slip made national news, and Theismann became the poster child for dumb jocks everywhere. But his remark really wasn't as dumb as it first appeared to be.
Research shows that most TOTs involve the unique names of people or places. If you're searching for a common noun—such as the name of the computer part that displays text—you can say monitor or screen. But for a proper name, only one word will do.
When a proper name is on the tip of our tongues, we can usually recall some of the information we need. For instance, people can often guess the right number of syllables in the name, even the name's first letter. In one study, a participant tried to identify a picture of the actress Liza Minnelli. The person couldn't produce her name but wrote out names that came tantalizingly close: Monetti, Mona, Magetti, Spaghetti, Bogette.
Another clue to the TOTs riddle is that recall of the right name is often blocked by a wrong name. But not just any wrong name. The wrong name typically has the same meaning as the right name. If you're thinking about a smart person like Albert Einstein, for instance, the wrong name will likely be that of another person you also consider very smart. This is where the Theismann story gets interesting.
There really is a Norman Einstein. He's an emergency room physician at Catawba Valley Medical Center in Hickory, North Carolina. He and Joe Theismann were classmates at South River High School in New Jersey.
"I was a senior when he was a sophomore," Dr. Einstein said. As boys, they lived just blocks apart. "We played a little bit of basketball, touch football-that kind of stuff." But they weren't close friends: Theismann was a jock, Einstein a brain. Einstein graduated in 1965 and was the class valedictorian. He attended Rutgers University and then medical school at Tufts University. Theismann headed to the NFL. Twenty-seven years later, in a corner of the Metrodome in Minneapolis, Norman Einstein's name popped back into Joe Theismann's head.
In Theismann's mind, the surface details regarding Norman Einstein and Albert Einstein may have faded, but their common meaning had not: Both were very smart guys.
2. We wear rose-colored glasses.
Without intentionally trying to distort the record, we're all prone to recalling our own words and deeds in a more favorable light than others may recall. To demonstrate, answer this question objectively (but only if you kept all your old report cards): How did you do in high school?
The answer: probably not as well as you remember—at least not if students at Ohio Wesleyan University are any guide. In one study, they were asked to recall their high school grades. Researchers checked the students' responses against the actual transcripts. No less than 29 percent of the recalled grades were wrong. This was not ancient history; the students were college freshmen and sophomores being asked about their grades just a few years earlier.
What's more, the errors weren't neutral. Far more grades were shifted upward (recalling an A rather than a B) than downward. Students also had a better memory for good grades than for bad. The recall accuracy for A's was 89 percent; for D's, it was 29 percent (researchers threw out the F's). Overall, 79 percent of students inflated their grades.
Time and again, people have been shown to reconstruct their memories in positive, self-flattering ways. Parents have been shown to remember their parenting methods as being far closer to what expert opinion would prescribe than they actually were. And gamblers remember their wins more keenly than their losses.
This inclination is so powerful that, according to researchers at the University of Chicago and the University of Virginia, we also recognize our own faces as being more physically attractive than others judge them to be.
3. When we multitask, we get stupid.
The brain slows down when it has to juggle tasks.
In one experiment, researchers asked adults between the ages of 18 and 32 to identify two images: colored crosses and geometric shapes, such as triangles. Seems simple enough, right? But when the participants saw colored crosses and shapes at the same time, they needed almost a full second of reaction time to press a button. Even then, they often made mistakes. If the participants were asked to identify the images one at a time—crosses first, then shapes—the process went almost twice as quickly.
Switching from task to task creates other problems. We can forget what we were doing or planned to do. The to-do list in our brains is known as working memory, and it keeps track of all the short-term stuff we need to remember, like an e-mail address someone just gave us.
But the contents of our working memory can evaporate like water in a desert; after only about two seconds, things begin to disappear. Within 15 seconds of considering a new problem, you'll have forgotten the old problem. In some cases, the forgetting rate can be as high as 40 percent. Workplace studies have found that it takes up to 15 minutes to regain a deep state of concentration after a distraction.
This squares with what researchers found when they looked at the work habits of Microsoft employees. A group of them took, on average, 15 minutes to get back to serious mental tasks, like writing reports or computer codes, after they responded to incoming e-mails. Why so long? Typically, the employees strayed off to reply to other messages or browse the Web.
In workplace cubicles, we're safe (most of the time). But out in the real world, multitasking can be dangerous. In 1999, the U.S. Army studied the effect talking on a cell phone had on driving ability. Its conclusion? "All forms of cellular phone usage lead to significant decreases in abilities to respond to highway traffic situations."
This was especially true for older drivers. The older we are, the harder it becomes to screen out distractions. The decline is noticeable after age 40.
4. We see, but we don't see.
Sometimes a person can look directly at something and still not see it. In experiments done in the early 1990s, researchers found that a surprising number of participants were unaware of certain objects that were presented to them in visual tests. This tendency held true not only when the presented objects were small but when they were large and quite obvious. (Consider, also, how eyewitness testimony persistently fails.)
A real-life demonstration of the "we see, but we don't see" mistake occurred in 2004 near Washington, D.C. On November 14, a 44-year-old charter bus driver picked up a group of students at the Baltimore/Washington airport for a trip to Mount Vernon, George Washington's home. By all accounts, the driver was in a bad mood that day. He was upset about the way another driver in the entourage was treating him. So he got on the phone and vented about it.
The students' route that morning took them along the George Washington Memorial Parkway. The parkway passes through rolling hills and beneath arched overpasses, including a stone bridge. About a quarter of a mile before it, a large yellow sign warns that the arched overpass ahead has a clearance of just over ten feet in the right-hand lane.
For cars, this is no problem. But the charter bus was 12 feet tall. The driver needed to move toward the center lane, under the peak of the arch, where the clearance is well over 13 feet. This is what the lead bus did.
Yet the second bus never changed lanes. The driver continued talking on the phone. The bus slammed into the bridge, and the collision sheared off the right side of the bus's roof, exposing a gaping hole. One student was seriously injured.
After the accident, the driver was interviewed by the National Transportation Safety Board. His statement shows the power of inattentional blindness. He told investigators that not only did he fail to see the yellow warning sign, he failed to see the bridge itself.
5. We notice on a need-to-know basis.
Often we fail to pick up major changes to scenes even while we're actually viewing them.
The profound impact of this "change blindness" was demonstrated a decade ago in an experiment by Daniel Simons and Daniel Levin, then at Cornell University. The experiment was simple: The researchers had strangers on a college campus ask pedestrians for directions. But there was a twist. As the stranger and the pedestrian talk, they're interrupted by two men who pass between them while carrying a door. The interruption is brief—it only lasts a second—but something important happens. One of the men carrying the door trades places with the stranger. When the door is gone, the pedestrian is confronted with a different person, who continues the conversation as if nothing had happened.
Would the pedestrians notice the change?
In more than half of the cases, the answer was no. Only seven of the 15 pedestrians reported noticing.
You may think, I would have noticed a change like that. And maybe you would have. But consider that you've probably seen countless similar changes and not noticed them—in the movies. Movie scenes, of course, are not filmed sequentially but shot in a different order than they appear in the film, usually months apart. This process often results in embarrassing mistakes known in the industry as continuity errors.
One of the most famous of these comes in the chariot scene in the 1959 Hollywood epic Ben-Hur, which lasts for 11 minutes but took three months to film. During the race, Messala damages Ben-Hur's chariot with his saw-toothed wheel hubs. But at the end of the race, if you look closely, you will see that Ben-Hur's chariot appears undamaged.
There's also a mix-up in the number of chariots. The race begins with nine; during the race, six crash. That should leave three at the end, but there are four.
Even experts cannot catch every mistake. "It's not humanly possible," says Claire Hewitt, who has supervised scripts on a variety of movies over the years. The best you can do, she says, is to try to spot the most important things.
6. We skim when we shouldn't.
Few industries make a habit of confessing their errors. But one does on a daily basis: newspapers. Their correction columns often make such delicious reading that in 2004 Craig Silverman, a freelance writer in Montreal, launched a website devoted to them, regrettheerror.com. Each year, he compiles the industry's greatest hits, as it were, into a book of the same name. A favorite was published a few years ago in the Wall Street Journal: "Some jesters in a British competition described in a page-one article last Monday ride on unicycles. The article incorrectly said that they ride on unicorns." How could the editors have missed that? While it's tempting to attribute mistakes like this to simple carelessness, the explanation is more complicated.
When we read an article, odds are, we don't read every single letter in every single word in every single sentence. We've read enough words and sentences that we can recognize patterns. If the sentence begins, "The thirsty man licked his …," the final word is probably lips. Likewise, if our eyes pick up a short word that begins with th-, we will probably assume that the final letter is e.
Human perception is, above all, economical; we notice some things and not others. And the better we are at something, the more likely we are to skim. Good sight readers of music don't read music note by note; they scan for familiar patterns and cues. This lets them play with the fluidity that other musicians must practice to achieve.
But with this ability comes a trade-off: Details are overlooked. Decades ago, a distinguished piano teacher, Boris Goldovsky, discovered a misprint in a much-used edition of a Brahms capriccio after a student played the note at a lesson. Goldovsky stopped the pupil and told her to fix her mistake. She looked confused; she had played what was written. To Goldovsky's surprise, there was an apparent misprint in the music. Why, he wondered, had no one—the composer, the publisher, the proofreader, other pianists—noticed the error? They had all misread the music and misread it in the same way. They had inferred a sharp sign in front of the note because in the musical context, it had to be a G-sharp, not a G-natural.
Goldovsky conducted his own experiment. He told skilled pianists that there was a misprint in the piece and asked them to find it. He allowed them to play the piece as many times as they liked. Not one musician found the error. (For music fans, the piece is Brahms's op. 76, no. 2. The mistake occurs in bar 78.)
7. We think we're better than we are.
When a Princeton University research team asked people to estimate how susceptible they and the "average person" were to judgmental biases, most people claimed to be less biased than others. Which should come as no surprise. Most of us hate to think of ourselves as average or, heaven forbid, below average. So we walk around with this private conceit that we're above average, and therein lies the seed of many of our mistakes. "Overconfidence is, we think, a very general feature of human psychology," says Stefano DellaVigna, an associate professor of economics at the University of California, Berkeley.
He's studied the ways in which overconfidence induces us to commit everyday errors of judgment, from signing up for gym memberships we'll never use to buying time-shares in a condo (which we also won't use, at least not as much as we think we will). "Nearly everyone is overconfident," he says, "except the people who are depressed. They tend to be realists."
Oddly, as tasks get harder, overconfidence tends to go up, not down. Even when given a nearly impossible job—like telling the difference between drawings by Asian children and those by European children—people think they'll perform better than they do.
So strong is our belief in our own abilities that we often believe we can control even chance events, such as flipping a coin or cutting a deck of cards. But it's an illusion of control. And it's not limited to those who make a living at the racetrack or in other high-stakes endeavors.
Corporate executives often display overconfidence in their judgments about the thing they think they know best: their businesses. In a well-known series of tests, managers were quizzed about their knowledge of their own industries; 99 percent proved overconfident.
Mistake-Proof Your Life
1. Think small. Each year in the United States, some 7,000 people die from medication errors—and many of them are made because of doctors' sloppy handwriting. Little things do mean a lot.
2.Think negatively. When you have a major decision to make, ask, What could go wrong? While putting a positive spin on things can influence their outcome, positive thinking also blinds us to pitfalls. So look for and even expect failure. It's "the power of negative thinking," says Atul Gawande, MD, of Harvard Medical School.
3. Think differently. Habit is a great friend, saving us time and mental effort. But it can kill our ability to perceive novel situations. After a while, we see only what we expect to see.
4. Slow down. Multitasking can cause our error rate to go up, as our attention becomes divided. It makes sense to slow down and do things one at a time. The slower approach may actually be more efficient in the long run.
5. Get more sleep. Sleepy people make mistakes, and there are staggering numbers of sleep-deprived people out there.
6. Beware anecdotes. When making decisions, we often give vivid bits of information-like diet testimonials—more credence than they deserve. The power of anecdotes to lead us astray is so strong that an influential CIA study advises intelligence analysts not to rely on them. Ask for averages, not testimonials.
7. Put off decisions until you're in a better mood. Good feelings increase the tendency to combine material in new ways and see relatedness between things. Happy people tend to be more creative and less prone to errors.
8. Use constraints. Simple mental aids keep us on the right track. The color red works well because this extreme and powerful color signifies "stop." A song's melody can be a constraint against forgetting; it's why jingles stay with us long after commercials do.
Why We Make Mistakes, Copyright © 2009 By Joseph T. Hallinan, is published at $24.95 by Broadway Books, 1745 Broadway, New York, New York 10019