Historians of science have demonstrated that almost all scientific discoveries can be assigned to one of just three scenarios. The first, the Archimedes scenario, is the most common and involves discoveries made in bathtubs or showers. Practicing scientists generally spend five to six hours each day in the bathtub (or Jacuzzi, in laboratories with particularly large grants from the National Institutes of Health), in the hopes of making a breakthrough akin to Archimedes’ discovery regarding the displacement of water. Upon such a discovery, the scientist typically leaps from the tub and runs through the lab, arms upraised, shouting in Greek.

The second, the It came to me in a dream scenario, also has a long pedigree, harking back to Friedrich Kekule’s discovery of the benzene ring after he dreamed of a snake swallowing its tail and dancing in a circle. Dreaming has been a fruitful route to scientific enlightenment and a major rationale for the frequent naps that scientists take when not splashing in bathtubs.

The third breakthrough scenario has the overworked scientist taking a night off from grappling with a vexing problem (or, more often, being forced to take a night off by a significant other) to attend the opera or symphony. During a quiet interlude (typically a flute solo), sudden insight dawns. Equations are hastily scribbled on program notes, and the person rushes to the exit while saying, My darling, I must return immediately to the laboratory (emphasis on second syllable, à la Anthony Hopkins). This is in reality the rarest of the major modes of discovery, but its frequency has been much inflated in movies, for several reasons: scenes of scientists sleeping lack cinematic potential; scantily clad scientists leaping from bathtubs are generally hard to market (the likes of Leonardo DiCaprio and Liv Tyler keep turning down the roles of Einstein and Curie); and the breakthrough-at-the-symphony scene comes with its own soundtrack.

All things considered, these three settings account for about 94 percent of important scientific breakthroughs. And the remaining instances? In some of them the scientist didn’t discover anything. Instead the lightbulb went off above someone else’s head, who came and told the professor about it.

One famous case involved Louis Leakey, the grand old man of paleontology, and his discovery of Zinjanthropus, the fossil skull that firmly established human origins in Africa. As it turned out, Leakey was lying sick in his tent when the skull was discovered by his wife, Mary. In that paleo-pc era, she was still decades away from being considered a scientist in her own right, so her discovery was credited to him.

In a similar vein, some discoveries have been made by the people who actually spend time around the study subjects that the scientists no longer have the time for (being too busy thinking about the big picture or, more likely, preparing their next grant proposal). This has happened a number of times at the Jackson Laboratories in Bar Harbor, Maine, a huge research facility that breeds mice for a variety of physiological or behavioral traits. Over the years, a mouse strain deficient in growth hormone has been developed there--because one of the animal technicians noticed a mouse that was a runt in its litter. A strain of congenitally deaf mice has been developed too--because another animal technician noticed a mouse that didn’t startle when two cages happened to bang together. At the Jackson Labs this pattern of discovery is so reliable that the staff hold regular meetings, charmingly known as deviant searches, to discuss whether the animal technicians have spotted anything odd among the mice.

One of the most consistent routes for the unlikely scientific discovery could be encapsulated in a snappy aphorism of the sort sometimes embroidered on pot holders: If you want to find out if the elephant in the zoo has a stomachache, don’t ask the veterinarian, ask the cage cleaner. People who have to clean up messes often become very attuned to the circumstances that change the amount of mess they have to clean up.

The Brattleboro rat is a good example. Normally mammals secrete the hormone vasopressin from the pituitary gland, and it tells the kidneys to retain water in the bloodstream. The Brattleboro rat, however, congenitally lacks vasopressin. As a consequence, it loses water and suffers from a terrible thirst and massive amounts of urination--diabetes insipidus. And who discovered the very first such rat, in a lab in West Brattleboro, Vermont? A scientist interested in renal function? A diabetes expert looking for animal models of the human disease? A researcher who, examining the values printed out by a laboratory instrument, spotted the odd electrolyte levels of the first such animal? No. It was the kid who cleaned the cages. Something’s wrong here--this rat is going through water ten times as fast as usual and peeing it all out, and I’m tired of having to change the bedding all the time. What’s the deal with this rat?

But my all-time favorite example of discovery by the person who cleans up the mess concerns a man whose identity is lost to history--a San Francisco upholsterer who just missed changing the course of medicine. It involves a finding by now so well entrenched in public awareness that it has been distorted beyond recognition: type A behavior, arguably the century’s central finding in behavioral medicine.

Certain personality types, we know, are linked to certain patterns of physiology or disease. The term type A behavior refers to a behavioral profile apparently associated with an increased risk of cardiovascular disease. A person with type A behavior, as first described by San Francisco cardiologists Meyer Friedman and Ray Rosenman, is immensely competitive, overachieving, time-pressured, impatient, insecure, and hostile, and suffers from low self-esteem. Despite some initial robust skepticism from more mainstream doctors, who thought about heart disease in the context of lipids and blood vessels and heart valves, the finding has been solidly validated, and type A behavior is now recognized to carry at least as much cardiac risk as does smoking or high cholesterol levels. And- -a sure sign of a healthy, important finding in science--research on type A-ness continues unabated.

A number of important questions about type A behavior remain to be answered. Among them: Which features of the personality profile are critical? Some think it’s the time-pressuredness, others the hostility. The latter crowd is eager to know whether expressed or unexpressed hostility is most chronically corrosive to the heart. Stay tuned.

There is also the question of how it is that a personality profile can translate into increased risk of heart disease. One scenario involves the physiological equivalent of turning molehills into mountains. Take a card-carrying type B person, put him in a frustrating social situation (say, a slow supermarket line), and soon he’s checking out the Elvis sightings in the tabloids. He’ll show hardly a blip of a rise in blood pressure at the frustration. Take a type A and she’ll rage (I’m late, I’m going to die someday and I can’t waste my life in supermarket lines, that weaselly little checkout kid is moving slowly just to screw up my day). Her blood pressure soars and stays up there for a while. No big deal if you do that once. But do that incessantly over a lifetime, turning every frustration into a hypertensive episode, and the cardiovascular system becomes more likely to pay a price someday.

If you can change the personality features of a type A, can you decrease the disease risk? The good news appears to be a resounding yes, while the bad news appears to be that it doesn’t come easy. (Distrust the ads in the tabloids being read languidly by the type B individual about how some expensive technique can banish type A-ness over a weekend.)

Meanwhile, experts have not begun to address perhaps the most challenging question: Why are people who talk loudly at parties about how type A they are, while certainly irritating to those around them, usually nowhere near as irritating as the people who talk loudly about their type B-ness?

Somewhere in all this, of course, is hidden the question of discovery: How did Friedman and Rosenman figure out the type A story to begin with? I recently had the privilege of hearing it from the horse’s mouth, from Meyer Friedman himself. At 86, he runs the Meyer Friedman Institute and is in the thick of ongoing research. A self-proclaimed type A, he suffered a heart attack at a relatively early age, then made some changes in his life. Cardiologists are not usually introspective and psychologically minded, but Friedman is a strong exception.

It’s the form of the introspection that struck me as relevant to this story. We discussed his work over the course of several visits, and though his demeanor is cordial and gentle to an extreme, he illustrated half his examples of type A-ness with a self-excoriating confessionalism. He told me all about what an angry, impatient, unappreciative S.O.B. he was in his prime, regaling me with tales of people he was curt to, whose efforts he never noticed, whose accomplishments he envied. His confessions took an almost religious tone at times, as if coronary blood vessels have become our ledgers of sin. (Happily for many of us, type A science has its parallels not with religions whose leaders gave signs of their saintliness from the time of their births, but with those in which dissolute youth finds redemption later in life.) As our conversations progressed, it occurred to me that Friedman might not be the most accurate narrator; I suspect that this kind and sensitive man has probably been that way his entire life, and that he’s way too hard on himself.

During those visits, Friedman told me about the discovery of the type A link. It was the mid-1950s, and he and Rosenman were having an unexpected problem with their successful cardiology practice: they were spending a fortune reupholstering the chairs in their waiting rooms. There seemed to be no end of chairs that had to be fixed. One day a new upholsterer came in to see to the problem, took one look at the chairs, and discovered the type A-cardiovascular disease link. He announced it semicryptically, with the words: What the hell is wrong with your patients? People don’t wear out chairs this way. The front-most few inches of the seat cushions and the armrests--and only the front-most few inches-- were torn to shreds, as if some very short beavers had spent the night in the office craning their necks to savage the chairs. Obviously these particular waiting rooms were far from peaceful places. The patients habitually sat on the edges of their seats while fidgeting and clawing away.

The rest should have been history. Upswelling music as the upholsterer is seized by the arms and held in a penetrating gaze--Good heavens, man, do you realize what you’ve just said? Hurried conferences between the upholsterer and other cardiologists. Frenzied, sleepless nights while teams of idealistic young upholsterers spread across the land, bringing back the news: Nope, you don’t see that wear pattern in the waiting rooms of the urologists, or the neurologists, or the oncologists, or the podiatrists--just the cardiologists. There’s something different about people who wind up with heart disease. And the field takes off.

However, none of that happened. Friedman sighs. Another confession: He didn’t pay any attention to the man, he tells me. He was too busy; it went in one ear and out the other. It wasn’t until four or five years later that Friedman’s formal research with his patients began to yield some hints, sparking a thunderclap of memory: Oh my god, the upholsterer! Remember that guy going on about the wear pattern?

Somewhere in San Francisco there’s no doubt a bar, probably by the docks, where in days gone by old, grizzled whalers would tell you the improbable stories of how they got their wooden legs. He sits there in the corner, usually by himself, a man who’s seen a lot of bad seat cushions but doesn’t necessarily feel the need to talk about them. Maybe, if a newcomer buys him a drink and he’s in the right mood, he might loosen up a bit. Truth be known, though, the regulars roll their eyes a bit at the old eccentric--Oh no, here comes that crazy story of his again--as he begins to tell the young ’un about the big fish that got away. Son, I can tell you haven’t seen much of the world, but you must have noticed there’s some folks who get all twitchy when the bank line’s moving slow. . . .