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/ Source: NBC News
By Maggie Fox

You knew it, you just knew it and it’s true: People who think they know everything make up stuff.

It’s what anyone arguing at a bar or family dinner has long suspected. People who overestimate what they know will claim to know about things they truly know nothing about.

Worse, they apparently don't even know that they don't know.

“At times, people even claim knowledge they cannot possibly have, because the object of their knowledge does not exist, a phenomenon known as overclaiming,” Stav Atir of Cornell University and colleague write in their report, published in the journal Psychological Science.

Studies have shown that people will overestimate what they know. Atir and colleagues set out to find out just how far it will go. They set up a series of experiments.

In the first, they offered an online test of people’s financial knowledge. They recruited 100 people to rate their general knowledge of personal finance, and they asked about 15 specific finance terms. Twelve of the terms were real: tax bracket, fixed-rate mortgage and so on. But three were just made up: “pre-rated stocks”, “fixed-rate deduction”, “annualized credit”).

“The more people believed they knew about finances in general, the more likely they were to overclaim knowledge of the fictitious financial terms,” Atir said in a statement.

For a deeper look, they recruited people on Amazon’s Mechanical Turk — a website the recruits people online to take tests for a small fee — to rate their knowledge about biology, philosophy, and literature, as well as mathematics, architecture, computer programming, and 20th-century art.

Then they asked real questions about these areas, as well as questions about made-up terms such as “meta-toxin”, “bio-sexual” and “retroplex”. They could give themselves anything from a 1: “never heard of it” to a 7: “very familiar”.

About 90 percent of the volunteers claimed to know something about at least one of the made-up terms, Atir’s team found. The more people claimed to know about a particular subject, the more likely they were to fall for the fake terminology.

It could be that people are doing this on purpose just because they want to seem smart. So they set up a test and warned people there would be bogus terms.

People who want to be seen as knowledgeable wouldn't want to be seen falling for fake terms, the researchers figured.

They again recruited people online, this time 97 of them. But most — 85 percent — again claimed to know about at least one of the made-up items. And again, the more expertise someone claimed, the likely more he or she was to claim knowledge about non-existent areas.

Finally, Atir’s team recruited 148 people to take a geography quiz. One-third got an easy quiz, a third got a hard quiz and a third got no quiz at first.

“The questions in the easy condition were meant to give participants the sense that they were relatively well traveled and well versed in U.S. geography because these participants were likely to answer “yes” (e.g., “Have you ever been to New York? Yes/No”) or to choose a high-numbered answer (e.g., “How many state capitals can you name?”) Atir’s team wrote.

“As a manipulation check, all participants then rated their knowledge of U.S. geography (1 = my geography knowledge is very weak, 10 = my geography knowledge is very strong).”

Then everyone was asked about 15 cities. Three don’t exist: Monroe, Montana; Lake Othello, Wisconsin; and Cashmere, Oregon.

People who got the easy quiz were more likely to rate themselves as well-versed in U.S. geography. And they were more likely to then claim they knew something about one of the nonexistent cities.

What may be going on is that people don’t stop to think about what they actually know, but rely on a kind of perception that they know about a subject in general, Air’s team concluded.

It’s not just annoying.

“Self-perceived experts may give bad counsel when they should give none. For instance, an individual considering a financial decision may consult a friend who expresses confidence in her financial knowledge,” Atir’s team noted.

“That friend may provide inappropriate advice because she fails to recognize her insufficient familiarity with the question. In other words, overclaiming may hinder people from truly achieving a valuable level of genuine knowledge.”