In a series of 11 experiments involving more than 2,200 people of all ages, the researchers found they could reliably identify narcissistic people by asking them a question with an attached note.
The question was - To what extent do you agree with this statement: "I am a narcissist." (Note: The word "narcissist" means egotistical, self-focused, and vain.)
Participants rated themselves on a scale of 1 (not very true of me) to 7 (very true of me).
Results showed that people's answer to this question lined up very closely with several other validated measures of narcissism, including the widely used Narcissistic Personality Inventory.
The difference is that this new survey - which the researchers call the Single Item Narcissism Scale (SINS) - has one question, while the NPI has 40 questions to answer.
"People who are willing to admit they are more narcissistic than others probably actually are more narcissistic," said Brad Bushman, co-author of the study and a professor of communication and psychology at The Ohio State University.
"People who are narcissists are almost proud of the fact. You can ask them directly because they don't see narcissism as a negative quality - they believe they are superior to other people and are fine with saying that publicly," Bushman said.
Understanding narcissism has many implications for society that extend beyond the impact on the individual narcissist's life, Konrath said.
Bushman emphasised that SINS shouldn't be seen a replacement for the longer narcissism questionnaires. The NPI and other instruments can provide more information to researchers, such as which form of narcissism someone has.
"But our single-item scale can be useful for long surveys in which researchers are concerned about people getting fatigued or distracted while answering questions and possibly even dropping out before they are done," Bushman said.
The study will appear in the journal PLOS ONE.