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THIS IS ONE STORY ABOUT THE COMEDY and tragedy of error. The time is the late 1980s, a cold winter night. The scene is a house somewhere in Pittsburgh, where two men and one woman, all scruffily dressed Pitt students, are trying to eat their dinner in peace.

What's disturbing the peace is their cat -- a kitten, actually, with the valiance of a tiger and the persistence of a door-to-door salesman. This pint-sized tabby leaps from the floor to the seat of a dining room chair, and then from the chair to the tabl e.

That's when the real trouble starts. The cat heads straight for the woman's barbecued chicken, but she scoops him up and transfers him to the floor. Undaunted, the cat walks a small circle, jumps back up on the chair, and begins again.

Finally, one of the men pulls the empty chair away from the table. Too small to jump straight to the table from the floor, this determined kitten jumps up on the chair again. Sizing up the distance from the chair to the table, he decides that he can leap the gap. He bounds across the chair and launches himself. Paws extended, he arcs through the air, and it looks as though he'll make it. He is a picture of agility and grace -- even as he sails toward the table's edge, comes within an inch, and misses. He hurtles underneath and drops to the floor with an awkward thud.

This is the comedy and the tragedy of error, comedy for the Pitt students and tragedy (or at least indignity) for the cat. What the cat's misadventure demonstrates is that the significance of an error depends on your point of view. This is an idea worth c onsidering because all too often we see mistakes merely as signs of inadequacy or incompetence. We often fail to see the benefits we could gain from a deeper understanding of error.

The reason that errors are worth studying closely is that they are almost never random. Instead, mistakes arise inevitably out of the workings of the world. Most of the errors in our lives take their shape from the ways that human beings think and learn.< p> In the worst cases, of course, errors cause disasters: train wrecks, computer failures, overdrawn bank accounts. But at the same time, errors can be a source of creative inspiration. (The lowercase-styling of the poet e. e. cummings' name, for instance, w as originally a printer's error, and another well-known poet, Elizabeth Bishop, once invented an imaginary character called the Manmoth by playing on a misspelling of "mammoth," a newspaper's typographical mistake.) In the laboratory, errors can yield une xpected results that provide clues to scientific mysteries. And sometimes, errors can even offer entertainment (often at the expense of someone else -- or someone else's cat).

Here, then, are four Pitt professors who seek the intimate connections between error and insight. Each of these scholars takes a unique approach to error, whether it's finding ways to understand and eliminate it, discovering how to learn from it, or simpl y enjoying it.

We join them now in their search for the meaning in mistakes.

RAJIV GUPTA, ASSOCIATE professor of computer science, sits with his hands on his desk, displaying an analytical calm that is characteristic of his line of work. He offers assurances that what he has to say about the proces s of debugging computer programs will be easy to understand. "Most of what we do in software," he says, "is common sense."

A bug, of course, is a problem in a computer program -- sometimes a typographical mistake, but often, Gupta emphasizes, a flaw in the way the program is designed. The results of computer bugs can range from incorrect data in a printout to the temporary fa ilure of a complex system such as a university's phone network. For this reason, Gupta, as a computer scientist, needs to understand a great deal about errors -- specifically, where they come from and how to track them down.

Pitt's computer science department has been internationally recognized both for its theoretical research about computers and for its more practical work, for instance in developing software. Gupta, as part of his research at Pitt, develops software tools that help to pinpoint the precise places in a computer program where something has gone wrong. To give a simple example, a debugging tool might make it possible to stop a program execution in the middle, and so discover whether a bug occurs earlier or lat er in the program.

Software developers, says Gupta, are always looking for better ways to keep bugs out of their programs. For such companies, making reliable software is a matter of economic survival. "If you get these bugs," he explains, " they could make your product go down the tubes." Furthermore, society as a whole counts more and more on software systems -- for instance in airplane flight controls and in hospital patient monitoring equipment , where reliability can be a matter of life and death.

For software to be considered reliable, it must function smoothly in a wide variety of situations. For example, if it's reliable, it won't break down when one piece of information is entered incorrectly. Software developers, therefore, try to foresee all of the ways the software might be used. Errors arise, Gupta says, when the developers, without realizing it, make certain assumptions -- for instance, that one part of the "code" will always be used before another. When these assumptions prove false, the result is a bug.

These errors, then, often arise from an ordinary human overconfidence. They happen when people think they know more than they actually do -- when they get too comfortable with their habitual conceptions of the world.

So the secret to catching errors is to catch false assumptions. For this reason, software companies usually have separate quality assurance departments. Says Gupta, "It's commonly the case that if a person who developed the software tests it, they won't f ind anything wrong." Software testers, on the other hand, will do all they can to "break" a program -- to invent situations where it shuts down or makes mistakes. What happens when two people try to access this program at the same moment in time? What hap pens when someone turns the machine off before completing the last steps of the program ?

But as a fundamental tenet of their profession, programmers acknowledge that no one will ever get all of the bugs out of a program. Inevitably, all computer software will contain some errors. The reason, says Gupta, is-inherent in the process. "Usually," he explains, "programs are intended to handle a potentially large number of situations. " But, of course, since the number is so large, one may not think of all of them. When writing software, a programmer tries to consider a broad range of subsets of sit uations, but these may not cover all of the possibilities. Says Gupta, "You can make the software good, but there's always the possibility that one very strange situation may arise."

"LET ME TELL YOU ABOUT two kinds of errors,"says Michelene Chi, professor of psychology, launching into the subject while she sorts the papers on her desk. "First, when people solve problems in a classroom, you typically g rade them for whether they give a right or a wrong answer. But in problem solving, students are doing a 'procedure,' a step-by-step solution. And in the last decade, there has been psychological research that starts to show that sometimes you need to try to understand the procedure that generated the error."

Like computer scientists, educational psychologists such as Chi struggle with the questions of why and how people make errors. Ultimately, they would like to help teachers and students catch and correct the errors that arise while people are trying to lea rn. And in the past decade, they have made great theoretical strides.

What's new is the idea that errors are often systematic rather than haphazard. In other words, a student who misses 20 questions on a test, may be making only one error -- that is, repeating one flawed procedure. "Instructionally," says Chi, "that means t hat you could correct that one procedure, if you know what it is, pretty easily."

The other kind of error Chi mentions is one that she considers in depth in her own research at Pitt's Learning and Research Development Center, one of the world's premier centers for educational research. The question she looks at is how people understand -- and misunderstand -- concepts, particularly scientific concepts such as the circulation of the blood or the process of evolution. People, no matter what age, tend to have trouble with certain scientific concepts. For example, many people mistakenly im agine heat to be a form of matter. (Medieval scholars, for instance, imagined an actual substance they called "caloric. ") Instead, it is more accurate to understand heat as an equilibrium-seeking process in which energy passes from hotter substances to c ooler ones. (For example, when your dinner cools off, it's not just losing heat. The heat energy from the food is passing to the cooler air around it.)

As an explanation for why science can be such a "bottleneck" for some, Chi theorizes that humans divide the world into several conceptual categories, such as "things," "process," and "intentions." According to Chi, misconceptions may happen because people more readily understand the world in terms of things than in terms of process.

This theory might explain the tendency to conceive of heat as a "thing." And, Chi notes, once a person has acquired the notion of heat as a substance, it's difficult for teachers to convey instead the idea of the passage of heat as a series of events. Chi believes that teachers might benefit students simply by raising the issue of conceptual categories: "We might want to start by saying that heat is not a 'thing' that flows around. Heat is really a process."

In another facet of her research, Chi has coined a term called self-explaining. Self-explaining is something students may do when they read a story or an informational passage. Students who self-explain interpret the material as they go, making inferences , relating their reading to things they already know. Chi's research has indicated that students learn material better if researchers ask them questions that prompt the students to interpret and explain the material to themselves.

"One simple connection between their research and this study," Chi says, "is the question of whether self-explaining can be so powerful as to bring about conceptual change." When she talks about inducing conceptual change, Chi refers to the challenging ta sk of teaching students to rethink their deeply held beliefs about the physical world -- of enabling people to reassign heat, for instance, from the "things" category to the "process" category. "Right now, we're sort of stuck at the crossroads where we do n't know how to induce conceptual change. We haven't succeeded," she concedes, "but then, we haven't tried."

MAGNIFIED IN THE 3 X 5 photo that Mike Kuziora holds in his hands, the fruit fly embryo floats, a beautiful egg-shaped mass banded by blue lines that are as regular and straight as the stripes on a referee's shirt. These r egions are blue because students in Kuziora's laboratory turned them that color by adding a chemical probe. This probe attaches to a specific variety of the genetic material RNA. The strips of RNA indicate that the embryo is already dividing itself into s egments.

Kuziora, an assistant professor of biology, marvels that this process of segmentation starts so early: "This is only a three-hour embryo. It's basically a bag of cells at this stage."

The question of how a developing organism divides itself into different parts -- how one region of cells becomes a head, for example, while a genetically identical region of cells becomes a leg -- is one of the most challenging problems in genetics today. And the answers will probably come, as many biological discoveries do, through a systematic study of error. In fact, Kuziora's line of research demonstrates how scientifically revealing errors can be.

"One of the biggest advantages of studying fruit flies," he says, "is that it's very easy to introduce mutations or errors in their DNA sequence with radiation or chemicals." To illustrate his point, he hefts down from a bookshelf a thousand-page book tha t lists all the mutations that have ever been recorded in fruit flies. The kind that interest him specifically are those that transform one body part to another. "You get some very strange-looking flies," he says, "that have legs growing out of their head s -- that's a very famous one -- or that have four wings instead of two.

"The remarkable thing," he goes on, "is that in the early 1980s people started looking at the genes connected with these mutations, and they discovered that there was one particular region of DNA that was very similar between these genes. And once they ha d that sequence, they looked at other species and found similar genetic sequences in everything from yeast to humans." Genes that contain this kind of region are known as homeotic genes. Homeotic genes play a regulatory role, signaling other genes to turn on and off. In the fruit fly embryo in Kuziora's photograph, as soon as the developing fly finishes dividing itself into segments, different homeotic genes will become active in each of the segments. By influencing the activity of other, nearby genes, th ese homeotic genes determine exactly which part of the organism will be built by the cells in a given region.

Kuziora studies the homeotic gene that is ordinarily active in the posterior abdominal segment of the fruit fly. When this gene is removed or altered, the posterior segment develops, instead, into a repeat of the middle of the insect s abdomen. By experim enting with mutations, Kuziora hopes ultimately to understand the biological process by which homeotic genes affect the development of organisms.

"Basically, the whole field of genetics is based on errors," he concludes. "The errors are in the negative for the animal, but they are to our benefit in the sense that we can look at them and understand more about how things normally should work."

IN AN OFFICE WHOSE WINdow looks out on lush greenery, Norman McWhinney, professor of English at the University of Pittsburgh at Greensburg, sits back and recounts the story of the water goat. Having heard that the article he's being interviewed for will include a section on computer bugs, he embarks on a tale about a computer program designed to translate technical materials from English into Russian. In some of the Russian materials, it seems, a strange term appeared seve ral times: "water goat." Eventually, someone examined the original document to find the source of this mysterious phrase. Says McWhinney, "They found out that it was a hydraulic ram."

For McWhinney, this is more than just a shaggy goat story. As a scholar, McWhinney has expertise in the areas of comedy and comic theory. (In addition to his academic interest in comedy, he has practical experience as an actor and stand-up comic. He has p erformed, he says with a charming smile, "at the Comedy Store in Hollywood, Zany's in Chicago, and the Greensburg YWCA. ") McWhinney's story reveals a crucial link between comedy and error. The humor lies in the way that errors take us by surprise. "What we expect from a computer is seriousness, " he says. " And what we get is something we did not expect."

McWhinney offers a way of seeing errors as something to be savored, as something that can bring us joy. Errors are often funny, he says, because they break the expected sequence of events. "If you take the word 'serious,"' he insists, "that means in a ser ies. And when you disrupt the series, the human reaction is laughter."

In fact, McWhinney sees laughter as the "essential human sign," the act that sets people apart from other living creatures. "I love the idea that children laugh before they talk," he says. This, in turn, reminds him of another story, this one from his own life. He recalls a day when his son, then a toddler, was playing in the living room, which was fenced off from the rest of the apartment by low, child-safe gates. "I was going from the living room to the kitchen, and I had to step over the gate," McWhinn ey says. "My foot caught on the gate, and -- I fell over." Although his son was too young to talk, he gave a laugh of sheer, knowing delight.

At this, McWhinney adds that, of course, errors are funny only when you have some intellectual or "comic" distance from them: "You have to be far enough away."

McWhinney also explores a state of mind that transcends the very concept of error. We reach this state of mind when we give up on "serious" notions of how things ought to happen and we accept the world as it is. Walt Whitman, writes McWhinney in Sex, T ime, and Laughter: A New Theory of the Comic, achieves this state of mind with the "total affirmation and total inclusiveness" of his poetry. And in Buddhism, the bodhisattva, having relinquished his intellectual distance from the rest of existence, s miles rather than laughs. The Buddha smiles gently because, in an infinite universe there is no such thing as an error. And without error, McWhinney says, there is no such thing as comedy: "There is nothing that is not in the series, " he explains. "Every thing is expected."

HERE IS ONE FINAL STORY about the comedy and tragedy of error. It takes place in the same house of Pitt students where we began, on that same cold winter night. Late in the evening, the woman student is sitting cross-legge d on her bed, writing a draft of a seven-page history paper due the next morning. She is scribbling her way through page four when the recently humiliated tabby cat marches, with unbroken spirit, into the room.

He slinks up into her lap and, in the interest of helping her finish her paper, bats ferociously at the top of her pen. By second nature, the woman scoops him to the floor, but seconds later he is back in her lap again.

The woman tries shutting him out of the room, but it's no use. Doggedly, the cat mewls outside the door. Finally, in a flash of brilliance, the woman decides that the only way she will be able to work in peace is if she can fool the kitten into going to s leep.

Setting her notebook aside, she stretches out on the bed, and the cat, who usually dozes off beside her at night, jumps up and settles down next to her. She will wait for him to fall asleep, and then get up and finish her paper. It looks as though the kit ten is about to be outwitted for the second time tonight. But several hours later, when the woman wakes up, there he sits, staring at her with deadpan amusement and triumph in his eyes.

We have seen how errors can be a source of problems, a source of insight, a source of joy. But even more, they can be a source of grace. In a sense, our errors are what make us bearable to one another. There's deep comfort in knowing that while you left y our lunch at home or lost your wallet, your friends will sympathize because they know that tomorrow it could be their turn.

We often talk about error as something that we need to "get away from." Perhaps we ought to consider it as something we need to move closer to. It is by embracing error -- by thinking through its causes, by getting to know both the good and the harm that it does -- that we can understand in greater depth the way things ought to be. Then we can begin to see more clearly the right ways of getting things done.

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