wisdom of crowds
the (optimistic) notion that people make better decisions in groups
The (overly optimistic) notion that crowds reach, on average, better decisions than individual people or small groups.
It's possible this may only be apparently true, a statistical mirage perhaps because most people pull down the average of the individual, thus lowering the threshold for perceived crowd wisdom.
The historical record doesn't shine all that favorably on crowds.
Crowds that aren't wise are, by social convention, usually called mobs, so the "wisdom of crowds" crowd are sheltered linguistically from confronting the mountain of historical evidence contravening this hypotheis.
Every authoritarian dystopia that hunanity has ever tried was powered by a crowd that was pretty sure it was right about something that it was, in fact, very wrong about.
The "wisdom of crowds" hypothesis also fails to properly account for much of human advancement (at least prior to the discovery of the scientific method) being the apparant result of singular great minds. Socrates, Isaac Newton, and Charles Darwin weren't multitudes.
Popularized by the 2004 book, The Wisdom of Crowds: Why the Many Are Smarter Than the Few and How Collective Wisdom Shapes Business, Economies, Societies and Nations by James Surowiecki, the idea has some merit. Certain carefully constructed experiments also seem to indicate that crowds have the potential to converge on something useful.
In practice, the nature of the minds (trained vs untrained, open vs closed, authoritarian vs liberal, informed vs uninformed), the nature of the task at hand, and the communications mechanisms available, all seem to, sometimes radically, alter the optimium group size for exemplary performance of a task, such as but not limited to reaching a wise decision.
[Editor's Note: I've long suspected that the ideal size for a trivia team is 5 or 6. Agile programming practicitioners believe that pair programming is an ideal organizational structure for writing code, though there is a growing interest in what's been called "mob" programming, where an entire team of five or six people including two or three programmers, a user experience designer, and a domain expert work together to produce the product, all around the same desk.]