No! I am not just like an American!

The study, which investigated the accuracy of national character stereotypes in 49 cultures around the world, carries significant implications, Mr. McCrae said.

"When stereotypes of national or ethnic groups are unfavorable, they can lead to prejudice, discrimination or persecution, of which history and the world today are full of tragic examples," the paper says.

The research compared people's descriptions of their "typical" compatriot to their own personality traits and those of a friend or loved one. The differences were often striking. (The study did not measure perceptions through the eyes of foreigners.) Canadians, for example, believe they are generally submissive. But when it came to assessing levels of assertiveness, Canadians and Americans had nearly identical scores -- which were a bit higher than the world average.

"That's probably as striking a contrast as you could ask for," Mr. McCrae said.

The "most discordant" results came from England, where people consider themselves to be reserved and conventional. However, those that took the test in England were actually extroverted and open to new experiences.

Czechs believe they are antagonistic and disagreeable, but they scored higher than most on measures of altruism and modesty. Indians say they are unconventional and open to a wide range of new experiences, but were more conventional than residents of other countries.

Some people actually lived up to their stereotypes. Germans, for example, consider themselves hard-working and industrious -- and the personality tests showed they were.

Heaven, the joke goes, is a place where the police are English, the mechanics German and cooks French. Hell is where the police are German, the mechanics French and the cooks English.

There's just one problem. A new study in the journal Science finds that our stereotypes about different cultures, whether positive or negative, are just plain unreliable.

"Overall, there's about zero overlap" between perception and reality, says Robert McCrae of the National Institute on Aging.

Researchers from around the world asked 3,989 people in 49 cultures to define their cultural character, then compared the self-assessments with separate personality profiles of those cultures conducted by psychologists, says Antonio Terracciano, also affiliated with the federal agency.

The researchers looked at cultures rather than nations. For example, French-speaking and German-speaking Swiss were considered separately.