Wisdom of the Crowds

  • Posted 06.25.08
  • NOVA scienceNOW

(This program is no longer available for online streaming.) In the early 1900s, British scientist Sir Francis Galton thought he was proving the ignorance of the masses when he noted that no one got the right answer at a country-fair competition in which entrants were asked to guess the exact weight of an ox. What Galton failed to realize was that the median of all the guesses produced close to the right answer—and showed the "wisdom of the crowd."

Running Time: 04:28



PBS Airdate: June 25, 2008

NEIL deGRASSE TYSON: In an election year, people might disagree about who makes the best candidate, but you don't hear much argument on the merits of democracy: that millions of average people can, together, make a wise decision.

It wasn't always so. In the early 20th century, this controversial Englishman, Sir Francis Galton, tried to statistically test whether mobs of common folk were capable of choosing well.

And, as our musical correspondent Rob Morsberger tells us, what Sir Francis actually found was that, mathematically, at least, there's often wisdom in a crowd.

ROB MORSBERGER (Correspondent): Sir Francis Galton was a nobleman

And scorned the common masses.

He thought that votes of governance

Should be left to higher classes.

He'd prove with all the data

From a contest inescapable,

Of guessing even simple things

That commoners were incapable.

CARNIVAL BARKER: Ladies and gentlemen, step right up.

ROB MORSBERGER: What kind of contest might it be?

CARNIVAL BARKER: Guess the ox's weight and see. Guess the weight correctly and win a prize!


ROB MORSBERGER: Said a little one.

ADULT IN CROWD: That's much too light, at least a ton.

ROB MORSBERGER: An eager crowd queued up to play,

Eight hundred made a guess that day.

MATT WINTERS: So he had 800 data points.

CARNIVAL BARKER: And now the ox's weight is exactly...eleven hundred ninety-eight pounds. There are no winners!


ROB MORSBERGER: Sir Francis knew the rabble

Would never guess the weight.

How might they judge important things,

If left to meet that fate?

With mathematics he would show

How far they went astray.

But in the end his theory

Was in total disarray.

Because a curve of all the guesses...

ANDREW GELMAN: Oh that curve? It's the cumulative distribution function of the normal distribution.

Sorry, that's what it's called.

(The crowd laughs.)

ROB MORSBERGER: ...because graphing all the guesses

And determining their mean...

MATT WINTERS: I think he was talking about the median.

ROB MORSBERGER: And determining their me-dee-een.

He showed that if the crowd were one, its estimate is keen.

He showed that if the crowd were one, its estimate is keen.

JIMMY WALES (Founder, Wikipedia): Keen, yes.

ROB MORSBERGER: That's because, while no individual guessed the actual weight, the average of all the individual guesses is exactly right.

ANDREW GELMAN (Columbia University): The average will generally be better than a randomly selected individual guess.

ROB MORSBERGER: The average of the masses assures us of success.

MATT WINTER: I think he was talking about the median.

ROB MORSBERGER: And the larger the number of guesses we toss in...

MELISSA SCHWARTZBERG:...the more likely we are to get the right answer about the oxen.

ROB MORSBERGER: His premature prognostication,

They cannot help but scoff.

JENNIFER HILL: Galton should have gathered more data before he went shooting his mouth off.

ROB MORSBERGER: Sir Francis' hypothesis was rocked by ignoramuses.

He lost the proof he had avowed.

He found the wisdom of the crowds.

KELLY RADER: If you have a group of people and they each have tiny bits of information, then you can learn a lot, if we could just gather all those bits together.

ROB MORSBERGER: It's just like Wikipedia.

JIMMY WALES: Well, this isn't exactly like Wikipedia. It's a little bit different.

MATT WINTERS: It could maybe be Wikipedia. You don't even need to be an expert, but if you know something, then you're able to contribute, and that entry is able to be that much more informed.

ROB MORSBERGER: Another sample of this fare...

JENNIFER HILL: Who wants to be a millionaire?

REGIS PHILBIN IMPERSONATOR: Yeah, the audience lifeline.

JENNIFER HILL: If the person feels like they can't answer the question by themself, ask the audience.

KELLY RADER: The audience is right over 90 percent of the time.

JENNIFER HILL: There you go.


ANREW GELMAN: The wrong Gelman...


ROB MORSBERGER: One by one we're not too smart,

But every guess it plays its part,

And when you add them up you'll find...

ROB MORSBERGER AND CROWD: The wisdom of the crowd.


Wisdom of the Crowds

Produced and Edited by
Vincent Liota

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This material is based upon work supported by the National Science Foundation under Grant No. 0638931. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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Neil deGrasse Tyson
Astrophysicist, American Museum of Natural History
Andrew Gelman
Columbia University www.columbia.edu/cu/polisci/fac-bios/gelman/faculty.html
Jimmy Wales
Founder, Wikipedia en.wikipedia.org/wiki/Jimmy_Wales

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