"We found that people who are narcissistic use Facebook in a self-promoting way that can be identified by others," said lead author Laura Buffardi, a doctoral student in psychology who co-authored the study with associate professor W. Keith Campbell.
In the study, around 130 Facebook users were given personality questionnaires. The researchers also analysed the content of the pages and had untrained strangers view the pages and rate their impression of the owner's narcissism.
It was found that the number of Facebook friends and wallposts on an individual's profile pages correlates with narcissism. According to Buffardi, this is consistent with how narcissists behave in the real world-having numerous yet shallow relationships.
She said that narcissists are also more likely to choose glamorous, self-promoting pictures for their main profile photos, while others are more likely to use snapshots.
In the study, even untrained observers could successfully detect narcissism. The researchers found that the observers used three characteristics - quantity of social interaction, attractiveness of the individual and the degree of self-promotion in the main photo - to form an impression of the individual's personality.
"People aren't perfect in their assessments, but our results show they're somewhat accurate in their judgments," said Buffardi.
Campbell said that Narcissism is a trait of particular interest because it obstructs the ability to form healthy, long-term relationships.
"Narcissists might initially be seen as charming, but they end up using people for their own advantage. They hurt the people around them and they hurt themselves in the long run," said Campbell.
He added: "Nearly all of our students use Facebook, and it seems to be a normal part of people's social interactions. It just turns out that narcissists are using Facebook the same way they use their other relationships - for self promotion with an emphasis on quantity of over quality."
The results of the study appear in the October issue of the journal Personality and Social Psychology Bulletin.