Put Away The Bell Curve: Most Of Us Aren't 'Average'
For decades, teachers, managers and parents have assumed that the performance of students and employees fits what's known as the bell curve — in most activities, we expect a few people to be very good, a few people to be very bad and most people to be average.
The bell curve powerfully shapes how we think of human performance: If lots of students or employees happen to show up as extreme outliers — they're either very good or very bad — we assume they must represent a skewed sample, because only a few people in a truly random sample are supposed to be outliers.
New research suggests, however, that rather than describe how humans perform, the bell curve may actually be constraining how people perform. Minus such constraints, a new paper argues, lots of people are actually outliers.
Human performance, by this account, does not often fit the bell curve or what scientists call a normal distribution. Rather, it is more likely to fit what scientists call a power distribution.
The study examined the performance of 633,263 people involved in four broad areas of human performance: academics writing papers, athletes at the professional and collegiate levels, politicians and entertainers.
"We looked at researchers, we looked at entertainers, we looked at politicians, and we looked at collegiate as well as professional athletes," Aguinis said in an interview. "In each of these kinds of industries, we found that a small minority of superstar performers contribute a disproportionate amount of the output."
In 186 out of 198 groups ranging from physics professors and Grammy nominees to cricketers and swimming champions, researchers Ernest O'Boyle Jr., of Longwood University's College of Business and Economics, and Herman Aguinis at Indiana University's Kelley School of Business found that a sizable number in the group were superstars.
These superstars, moreover, accounted for much of the success of the group as a whole. The vast majority of the others in the group, Aguinis said, were actually performing below the mathematical average.
More than 80 percent of all Emmy-nominated entertainers, for example, fell below the mean in terms of the number of nominations they received. A small but sizable minority, meanwhile, enjoyed outsize success and accounted for a disproportionately large number of Emmy nominations.
Aguinis said the bell curve may describe human performance in the presence of some external constraint — such as an assembly line that moved at a certain speed.
"If you had a superstar performer working at your factory, well, that person could not do [a] better job than the assembly line would allow," Aguinis said. "If you unconstrain the situation and allow people to perform as best as they can, you will see the emergence of a small minority of superstars who contribute a disproportionate amount of the output."
Aguinis said his findings were descriptive, not prescriptive. He said the findings should not be interpreted to mean that managers and teachers should only focus on the superstars and ignore everyone else.
At the same time, he said, successful companies and nations would do well to identify superstars, because such performers were disproportionately likely to register new discoveries and achievements.
DAVID GREENE, HOST:
In Garrison Keillor's "Lake Wobegone," all the children are above average. That's a joke, of course. We know most children, like most adults, are not above average. In every human activity, we expect to find some people who are very good, some people who are very bad, and most people to be average.
But there's new research out into human performance that challenges our beliefs. To help explain it, we've called in NPR science correspondent Shankar Vedantam, who regularly joins us to discuss interesting social science research. Shankar, welcome back.
SHANKAR VEDANTAM, BYLINE: Hi, David.
GREENE: So what's this research about?
VEDANTAM: So, you know, there's been a half of century of research that suggests in every field of human activity, you're going to get some people who are very good, some people who are very bad, and most people in the middle. It's the familiar bell curve. So if you look at education or athletics, this is how human performance generally works.
GREENE: The curve where you see that middle just - sort of building up in the middle, as if it were a bell.
VEDANTAM: Exactly. It looks a little like a hill - where you have a tall peak in the middle, and you have the ends tapering off. So I spoke with a psychologist. His name is Herman Aguinis. He's at the Kelley School of Business at Indiana University, and he has some research that threatens to overturn our beliefs about the bell curve. So he's looked at the performance of more than 600,000 people in four broad areas of human performance. And here's what he's found.
HERMAN AGUINIS: We looked at researchers, we looked at entertainers, we looked at politicians, and we looked at collegiate as well as professional athletes. In each of these kinds of industries, we found that a small minority of superstar performers contribute a disproportionate amount of the output.
VEDANTAM: So what Aguinis is saying is that the performance of the people across these different fields did not fit the bell curve. He didn't find a few incompetent people, a few superstars, and lots of people in the middle. Rather, what he found was that most people are actually below average, and a small but fairly sizable number of superstars accounts for most of the performance - whether you're talking about home runs or academic papers or Oscar nominations.
GREENE: We seem to be talking about a lot of fields here - I mean, across life. And you're saying that in general, most of us are below average. That's a bit disturbing, in a way.
(SOUNDBITE OF LAUGHTER)
VEDANTAM: Well, it's not my conclusion. It's a conclusion that disturbs me as well, but it is what Aguinis is finding. So if you look at the universe of, say, 3,000 Grammy nominations, what you'd expect to see is that a few people would receive one or two nominations; lots of people would receive three or four nominations; and fewer than five would receive more than 10 nominations.
Instead, what Aguinis is finding is that most people receive only one Grammy nomination, and a small but fairly sizable number - 64 people - receive more than 10 nominations.
GREENE: Well, Shankar, before we throw out years of research - I mean, I have to ask; the bell curve certainly came from something. I mean, all the times performance was measured in schools and workplaces - I mean, what happens to all of that research?
VEDANTAM: So what Aguinis is basically saying is that much of the time, what we are doing is, we are not measuring human performance as much as we're constraining it. So when we force people into the bell curve, what this does is it eliminates the performance of people who are the superstars. And he says this is a crazy idea because the bell curve came to us from this 19th century idea of how a factory assembly line is supposed to work. Here's what he told me.
AGUINIS: If you had a superstar performer working at your factory, well, that person could not do a better job than the assembly line would allow. If you un-constrain the situation and allow people to perform as best as they can, you will see the emergence of a small minority of superstars who contribute a disproportionate amount of the output.
VEDANTAM: What Aguinis is saying is that when you're working an assembly line, you can make only so many widgets in an hour because that's how fast the assembly line is moving. But today, most people are not working in an assembly line. And so there is, theoretically, no limit on the number of academic papers you can write, or the number of home runs you can hit, or the number of Grammy nominations you can receive.
GREENE: So in this current world, if we're not talking all the time about an assembly line, I mean, would he say that we should just be focusing on the superstars and what they're able to do?
VEDANTAM: You know, it depends if productivity is your only goal. So if you think about education, for example, it would be absurd to say that we should only focus on the superstars, and kick everybody else out of school - because the goals of education are not just to win Nobel Prizes. But, he says, if your goal is to win Nobel Prizes or Grammy nominations then yes, you're disproportionately likely to get most of those victories from a fairly small number of superstars.
GREENE: Shankar, thanks for sharing this research with us.
VEDANTAM: Thank you, David.
GREENE: Shankar Vedantam, who regularly joins us to share interesting research on topical issues. You can follow him on Twitter @hiddenbrain, and you can follow this program @nprgreene and @morningedition. Transcript provided by NPR, Copyright NPR.